matrix metalloproteinases ( mmps ) are zinc - dependent proteases that are involved not only in the degradation and remodeling of the extracellular matrix but also in processing bioactive molecules , including cell surface receptors , neurotrophic factors , chemokines , and cytokines ( kim and joh , 2012 ) . mmps are indispensable enzymes for various physiological processes such as embryogenesis , morphogenesis , tissue reconstruction , and regulation of inflammatory processes under a variety of conditions ( nissinen and kahari , 2014 ) . mmps belong to a family of more than 25 enzymes , and each has their own activating cascade with mmp-2 and mmp-9 at the core . among mmps , gelatinases , including mmp-2 and mmp-9 , are similar in structure and are able to enzymatically process various substrates of the extracellular matrix , such as gelatin , collagen i and collagen iv ( sbardella et al . , 2012 ) . constitutively expressed in most cell types , mmp-2 has a prohomeostatic property , whereas mmp-9 is expressed at low levels in most cell types but is highly responsive to stimulation and has proinflammatory properties ( van den steen et al . , 2002 ; these enzymes are also known to be related to pathological processes such as cancer , neurodegenerative disorders , arthritis , and cardiovascular diseases ( sbardella et al . , 2012 ) . in the central nervous system , mmps play important roles in synaptogenesis , synaptic plasticity , and long - term potentiation ( ethell and ethell , 2007 ) . in contrast , there are limited studies of the role of mmps in psychiatric disorders . the mmps are endogenously inhibited by the tissue inhibitors of mmps ( timps ) . in humans , the c - terminal domain of timp-1 and timp-2 binds to the hemopexin of the proenzymes of mmp-9 and mmp-2 , respectively ( carlo , 2014 ) . this indicates that timp-1 and timp-2 are major individual inhibitors of mmp-9 and mmp-2 ( goldberg et al . , 1992 ) . mood disorders ( mds ) have been recognized as having a strong association with chronic inflammatory states ( rosenblat et al . , 2014 ) . in depression , fatigue and somatic symptoms such as gastrointestinal symptoms , autonomic symptoms , and flu - like malaise are significantly associated with signs of an activated inflammatory pathway ( maes et al . , 2012 ) . several studies have reported an association between depressive symptoms and state - dependent elevated levels of inflammatory markers , such as interleukin-1 beta , interleuki-6 , and tumor necrosis factor - alpha ( felger and lotrich , 2013 ; rosenblat et al . , 2014 ) . mmps process cytokines , which leads to alterations of their activity ( van lint and libert , 2007 ) . at the same time , the expression of mmps , mmp-9 in particular , is regulated by cytokines ( harkness et al . , 2000 ) . the current study sought to find an association between md and inflammation - related markers . the main mmps , mmp-2 and mmp-9 , and their inhibitors , timp-2 and timp-1 , were quantified in patients with md . first , serum levels of mmp-2 , mmp-9 , timp-2 , and timp-1 from patients with md who had depressive episodes and were eligible for electroconvulsive therapy ( ect ) were compared with healthy controls and patients with schizophrenia - spectrum disorders ( scz ) , who also had psychotic episodes and were also eligible for ect . serum levels of mmp and timp were then compared before and after a course of ect in patients with md and scz . finally , an association between serum levels of mmps and timps with clinical symptoms in patients with md and scz was determined . this study was conducted at the department of psychiatry of the national hospital organization kure medical center between january 2011 and april 2013 . thirty - four patients ( 12 men and 22 women , mean age  sd=54.116.1 ) were recruited among inpatients planning to receive ect based on the guidelines of the american psychiatric association ( 2001 ) . ect is often proscribed when a patient exhibits episodes of severe major depression , psychosis , and catatonia or has shown insufficient improvement with prescribed pharmacotherapy treatment ( american psychiatric association , 2001 ) . twenty - one patients were diagnosed as having md , either major depressive disorders ( n=11 ) or bipolar disorders ( n=10 ) , with a current episode of major depression . thirteen patients were diagnosed with scz , either schizophrenia ( n=10 ) or schizoaffective disorder ( n=3 ) , with symptoms currently exacerbated to psychosis , such as delusions , and catatonia . various types of schizophrenia were diagnosed , including catatonic ( n=5 ) , paranoid ( n=4 ) , and undifferentiated ( n=1 ) . patients with a past or present history of substance abuse , substance dependence , significant neurological illness , or any other significant medical illness were excluded from participation in the current study . a clinical psychiatrist recommended ect to each patient according to standards recommended by the american psychiatric association task force and based on the patient s urgency and severity of illness . forty healthy subjects ( 14 men and 26 women , mean age 54.213.9 years ) , with no history of past or current mental disorders were recruited as a control group . after procedures were fully explained , written informed consent was obtained from all subjects to participate in the study . the current study was approved by the ethics committee of national hospital organization kure medical center . ect was performed according to procedures from a previous report ( shibasaki et al . , 2015 ) . before undergoing ect , each patient was screened for general health through a physical and neurological examination , blood and urine tests , electrocardiogram , chest x - ray film , and a cerebral computed tomography scan . thiamylal sodium ( 23mg / kg , i.v . ) and suxamethonium chloride ( 0.51mg / kg , i.v . ) . the ect device used was the thymatron system iv brief pulse square wave apparatus ( somatics inc ) . only one adequate seizure was required for each session , which was defined as an electroencephalographic seizure lasting more than 25 seconds with a high - amplitude , slow wave , and postictal suppression . the initial stimulus dose was determined using the half - age method ( petrides and fink , 1996 ) . if an adequate electroencephalographic seizure occurred in one session , the stimulus energy of the next session remained the same . when a missed or inadequate seizure occurred , the patient was restimulated after a 20- to 30-second pause and the stimulus increased 1.5- to 2.0-fold . if any adverse effects ( eg , cognitive dysfunction , delirium ) occurred , the frequency of the ect schedule was reduced to once or twice per week . ect continued until the patient was asymptomatic or the attending psychiatrist determined that the patient had obtained the maximum benefit within 3 to 15 sessions . after the purpose and the ect procedure were described in detail , written informed consent was obtained from patients or caregivers of patients prior to initiating ect . most of patients with md ( 20/21 patients ) received antidepressant pharmacotherapy before ect : duloxetine ( 2060mg / d ; n=8 ) , mirtazapine ( 1545mg / d ; n=8 ) , paroxetine ( 2040mg / d ; n=4 ) , sertraline ( 25100mg / d ; n=2 ) , mianserin ( 1060mg / d ; n=5 ) , trazodone ( 2575mg / d ; n=3 ) , imipramine ( 50mg / d ; n=1 ) , or nortriptyline ( 100mg / d ; n=2 ) . nine subjects were on a stable dose of antidepressant during ect , 8 subjects had antidepressant dosage decreased during the course of ect , and 3 subjects had antidepressant dosage increased during the course of ect . eleven of 21 patients with md also took an antipsychotic medication ( either olanzapine or quetiapine ) before the course of ect to control either psychomotor agitation or psychotic symptoms . eleven of 13 patients with scz received antipsychotic pharmacotherapy before the course of ect : risperidone ( 1.512mg / d ; n=7 ) , olanzapine ( 1020mg / d ; n=4 ) , quetiapine ( 300675mg / d ; n=4 ) , zotepine ( 150400mg / d ; n=3 ) , blonanserin ( 1224mg / d ; n=2 ) , aripiprazole ( 24mg / d ; n=1 ) , haloperidol ( 30mg / d ; n=1 ) , chlorpromazine ( 450mg / d ; n=1 ) , or i.v . 3 subjects were on a stable dose of antipsychotics , 7 subjects had antipsychotics dosage decreased , and 3 subjects had antipsychotics dosage increased . clinical symptomatic scores were assessed using the 17-item ( hamilton rating score for depression [ hamd ] ) for patients with md and the brief psychiatric rating scale ( bprs ) for patients with scz . hamd 17-items were assigned to the following 5 subscales : core symptom ( items 1 , 2 , 7 , 8 , 10 , 13 ) ; sleep ( items 4 , 5 , 6 ) ; activity ( items 7 , 8) ; psychic anxiety ( items 9 , 10 ) ; and somatic anxiety ( items 11 , 12 , 13 ) in accordance with a previous report ( seretti et al . each patient s symptoms were assessed prior to the first ect session ( baseline , pre - ect ) and a day after the last ect session ( post - ect ) by the same psychiatrist . responders to ect were defined as demonstrating a 50% decrease in hrsd score in md patients or a 30% decrease in bprs score in scz patients . venous blood samples were taken in the morning ( between 7:00 and 8:00 am ) at pre - ect and post - ect . they were kept at room temperature for 1 hour , and serum was separated by centrifugation at 3000rpm for 15 minutes at 4c . serum levels of mmp-2 , mmp-9 , timp-1 , and timp-2 were measured using elisa ( quantikine elisa , r&d systems , minneapolis , mn ) according to the manufacturer s instructions . the data are shown as the mean  sd . the normal distribution of data was tested by the shapiro - wilk and the kolmogorov - smirnov tests , and statistical analysis was performed by nonparametric tests . a kruskal - wallis test was used to evaluate the significant difference in the parameters ( clinical and laboratory values ) among the 3 groups ( md , scz , and control ) . significant differences in the parameters between the 2 groups of patients with md and scz were evaluated using the mann - whitney u - test . a wilcoxon signed - rank test was used to evaluate the statistical differences in the parameters between pre - ect and post - ect . the receiver operating characteristic ( roc ) curves for the assessment of specificity and sensitivity of mmps and timps were calculated to discriminate between the md group and the control group . the areas under the roc curve ( auc ) were calculated for each mmps and timps as well . statistical significance after logistic regression between the 2 aucs statistical analysis was conducted by logistic regression , analyzing diagnosis value of single and combined detection of mmps . analyses were performed using spss version 22.0 for windows ( ibm japan corporation , tokyo , japan ) . this study was conducted at the department of psychiatry of the national hospital organization kure medical center between january 2011 and april 2013 . thirty - four patients ( 12 men and 22 women , mean age  sd=54.116.1 ) were recruited among inpatients planning to receive ect based on the guidelines of the american psychiatric association ( 2001 ) . ect is often proscribed when a patient exhibits episodes of severe major depression , psychosis , and catatonia or has shown insufficient improvement with prescribed pharmacotherapy treatment ( american psychiatric association , 2001 ) . twenty - one patients were diagnosed as having md , either major depressive disorders ( n=11 ) or bipolar disorders ( n=10 ) , with a current episode of major depression . thirteen patients were diagnosed with scz , either schizophrenia ( n=10 ) or schizoaffective disorder ( n=3 ) , with symptoms currently exacerbated to psychosis , such as delusions , and catatonia . various types of schizophrenia were diagnosed , including catatonic ( n=5 ) , paranoid ( n=4 ) , and undifferentiated ( n=1 ) . patients with a past or present history of substance abuse , substance dependence , significant neurological illness , or any other significant medical illness were excluded from participation in the current study . a clinical psychiatrist recommended ect to each patient according to standards recommended by the american psychiatric association task force and based on the patient s urgency and severity of illness . forty healthy subjects ( 14 men and 26 women , mean age 54.213.9 years ) , with no history of past or current mental disorders were recruited as a control group . after procedures were fully explained , written informed consent was obtained from all subjects to participate in the study . the current study was approved by the ethics committee of national hospital organization kure medical center . ect was performed according to procedures from a previous report ( shibasaki et al . , 2015 ) . before undergoing ect , each patient was screened for general health through a physical and neurological examination , blood and urine tests , electrocardiogram , chest x - ray film , and a cerebral computed tomography scan . thiamylal sodium ( 23mg / kg , i.v . ) and suxamethonium chloride ( 0.51mg / kg , i.v . ) . the ect device used was the thymatron system iv brief pulse square wave apparatus ( somatics inc ) . only one adequate seizure was required for each session , which was defined as an electroencephalographic seizure lasting more than 25 seconds with a high - amplitude , slow wave , and postictal suppression . the initial stimulus dose was determined using the half - age method ( petrides and fink , 1996 ) . if an adequate electroencephalographic seizure occurred in one session , the stimulus energy of the next session remained the same . when a missed or inadequate seizure occurred , the patient was restimulated after a 20- to 30-second pause and the stimulus increased 1.5- to 2.0-fold . if any adverse effects ( eg , cognitive dysfunction , delirium ) occurred , the frequency of the ect schedule was reduced to once or twice per week . ect continued until the patient was asymptomatic or the attending psychiatrist determined that the patient had obtained the maximum benefit within 3 to 15 sessions . after the purpose and the ect procedure were described in detail , written informed consent was obtained from patients or caregivers of patients prior to initiating ect . most of patients with md ( 20/21 patients ) received antidepressant pharmacotherapy before ect : duloxetine ( 2060mg / d ; n=8 ) , mirtazapine ( 1545mg / d ; n=8 ) , paroxetine ( 2040mg / d ; n=4 ) , sertraline ( 25100mg / d ; n=2 ) , mianserin ( 1060mg / d ; n=5 ) , trazodone ( 2575mg / d ; n=3 ) , imipramine ( 50mg / d ; n=1 ) , or nortriptyline ( 100mg / d ; n=2 ) . nine subjects were on a stable dose of antidepressant during ect , 8 subjects had antidepressant dosage decreased during the course of ect , and 3 subjects had antidepressant dosage increased during the course of ect . eleven of 21 patients with md also took an antipsychotic medication ( either olanzapine or quetiapine ) before the course of ect to control either psychomotor agitation or psychotic symptoms . eleven of 13 patients with scz received antipsychotic pharmacotherapy before the course of ect : risperidone ( 1.512mg / d ; n=7 ) , olanzapine ( 1020mg / d ; n=4 ) , quetiapine ( 300675mg / d ; n=4 ) , zotepine ( 150400mg / d ; n=3 ) , blonanserin ( 1224mg / d ; n=2 ) , aripiprazole ( 24mg / d ; n=1 ) , haloperidol ( 30mg / d ; n=1 ) , chlorpromazine ( 450mg / d ; n=1 ) , or i.v . 3 subjects were on a stable dose of antipsychotics , 7 subjects had antipsychotics dosage decreased , and 3 subjects had antipsychotics dosage increased . clinical symptomatic scores were assessed using the 17-item ( hamilton rating score for depression [ hamd ] ) for patients with md and the brief psychiatric rating scale ( bprs ) for patients with scz . hamd 17-items were assigned to the following 5 subscales : core symptom ( items 1 , 2 , 7 , 8 , 10 , 13 ) ; sleep ( items 4 , 5 , 6 ) ; activity ( items 7 , 8) ; psychic anxiety ( items 9 , 10 ) ; and somatic anxiety ( items 11 , 12 , 13 ) in accordance with a previous report ( seretti et al . , 1999 ) . each patient s symptoms were assessed prior to the first ect session ( baseline , pre - ect ) and a day after the last ect session ( post - ect ) by the same psychiatrist . responders to ect were defined as demonstrating a 50% decrease in hrsd score in md patients or a 30% decrease in bprs score in scz patients . venous blood samples were taken in the morning ( between 7:00 and 8:00 am ) at pre - ect and post - ect . they were kept at room temperature for 1 hour , and serum was separated by centrifugation at 3000rpm for 15 minutes at 4c . serum levels of mmp-2 , mmp-9 , timp-1 , and timp-2 were measured using elisa ( quantikine elisa , r&d systems , minneapolis , mn ) according to the manufacturer s instructions . the data are shown as the mean  sd . the normal distribution of data was tested by the shapiro - wilk and the kolmogorov - smirnov tests , and statistical analysis was performed by nonparametric tests . a kruskal - wallis test was used to evaluate the significant difference in the parameters ( clinical and laboratory values ) among the 3 groups ( md , scz , and control ) . significant differences in the parameters between the 2 groups of patients with md and scz were evaluated using the mann - whitney u - test . a wilcoxon signed - rank test was used to evaluate the statistical differences in the parameters between pre - ect and post - ect . the receiver operating characteristic ( roc ) curves for the assessment of specificity and sensitivity of mmps and timps were calculated to discriminate between the md group and the control group . the areas under the roc curve ( auc ) were calculated for each mmps and timps as well . statistical significance after logistic regression between the 2 aucs was determined . statistical analysis was conducted by logistic regression , analyzing diagnosis value of single and combined detection of mmps . analyses were performed using spss version 22.0 for windows ( ibm japan corporation , tokyo , japan ) . the clinical data of the 3 groups ( md , scz , and control ) are presented in table 1 . patients with md were significantly older and their duration of illness was shorter compared with the scz group . duration of current episode , number of ects , and duration of the ect course did not differ between the md and scz groups . there were no differences between the dose equivalence of imipramine of pre - ect and post - ect in the md group and also no differences between the dose equivalence of chlorpromazine of pre - ect and post - ect in the scz group . subject clinical data abbreviations : bprs , brief psychiatric rating scale ; cpz , chlorpromazine ; ect , electroconvulsive therapy ; hamd , hamilton rating score for depression ; imi , imipramine ; md , mood disorder ; scz : schizophrenia - spectrum disorder . comparison between scores at pre - ect and those at post - ect by wilcoxon signed - rank test . serum levels of mmp-2 in the md group with depressive episodes at pre - ect were significantly lower than those of the control group ( figure 1a ; p=.023 ) , whereas there were no significant differences for the serum levels of timp-2 , mmp-9 , and timp-1 between the md group and the control group ( figure 1b - d ) . serum levels of mmp-2 , mmp-9 , timp-1 , and timp-2 in the md group at pre - ect were not significant different compared with those of the scz group with psychotic episodes at pre - ect . additionally , serum levels of mmps and timps were not significantly different between md patients with either md ( unipolar ) or bipolar disorder ( bipolar ) at pre - ect ( mmp-2 , unipolar=165.925.0ng / ml vs bipolar=159.426.8ng / ml , p=.512 ; timp-2 , 63.17.6ng / ml vs 66.66.2ng / ml , p=.259 ; mmp-9 , 553.9218.8ng / ml vs 604.6310.5ng / ml , p=.668 ; timp-1 , 150.539.4ng / ml vs 148.023.2ng / ml , p=.571 ) . scatter plot of serum levels of matrix metalloproteinases ( mmps ) and tissue inhibitors of mmps ( timps ) . mmp-2 ( a ) , timp-2 ( b ) , mmp-9 ( c ) , and timp-1 ( d ) in controls (  ) , mood disorders ( md ) group before a course of ect ( pre - ect ,  ) and after a course of ect ( post - ect ,  ) , and schizophrenia - spectrum disorders ( scz ) group pre - ect (  ) and post - ect (  ) . the horizontal bars represent the mean values . in the roc curve analysis of diagnosis , the auc of mmp-2 , mmp-9 , timp-1 , and timp-2 at pre - ect between the md and control groups were 0.738 , 0.603 , 0.674 , and 0.675 , respectively . the scores for depressive symptoms evaluated by hamd in the md group and the scores of psychotic symptoms evaluated by bprs in the scz group significantly decreased following ect ( table 1 ) . both nonresponding scz patients were diagnosed with paranoid - type scz . there was a statistically significant increase in serum levels of mmp-2 in the md group over the course of ect ( p=.046 ) but no significant change observed in the scz group ( p=.650 ) ( figure 1a ) . there were statistically significant decreases in serum levels of mmp-9 in both the md and scz groups following ect ( md group , p=.003 ; scz group , p=.019 ) ( figure 1c ) . among the 2 nonresponders to ect in the scz group , one patient had an increase in serum level of mmp-9 and the other had a decrease in serum level of mmp-9 after the course of ect ( data not shown ) . serum levels of timp-2 and timp-1 did not significantly change over the course of ect in both the md and scz groups ( figure 1b , d ) . no significant correlations were observed in the md group between subject characteristics ( gender , age , age of onset , duration of illness , duration of current episode , or dose of medication ) and serum levels of mmp-2 , mmp-9 , timp-1 , and timp-2 at either pre - ect or post - ect ( data not shown ) . correlation coefficients were calculated between serum levels of mmps and timps and clinical symptomatic scores evaluated by hamd for md and by bprs for scz , combining results from pre - ect and post - ect ( table 2 ) . in the scz group , there was no significant correlation between serum levels of mmps , timps , and total bprs scores ( table 2 ) . in the md group , serum levels of timp-1 and timp-2 did not correlate with total hamd score ( table 2 ) . furthermore , no significant correlations were observed between timps and subscale hamd scores ( table 3 ) . correlation between mmp and timp serum levels and clinical symptomatic scores of md and scz groups abbreviations : bprs : brief psychiatric rating scale ; hamd , hamilton rating score for depression ; md , mood disorder ; mmp , matrix metalloproteinase ; scz , schizophrenia - spectrum disorder ; timp , tissue inhibitor of mmp . correlation between mmp and timp serum levels and subscale hamd scores in md groups abbreviations : hamd , hamilton rating score for depression ; md , mood disorder ; mmp , matrix metalloproteinase ; timp , tissue inhibitor of mmp . however , in the md group , there was a significant negative correlation between serum levels of mmp-2 and total hamd score ( p=.041 ) ( table 2 ; figure 2a ) and a significant positive correlation between serum levels of mmp-9 and total hamd score ( p=.006 ) ( table 2 ; figure 2b ) . furthermore , negative correlations between serum levels of mmp-2 and subscale hamd scores ( core symptom , activity , somatic anxiety ) were observed as well as positive correlations between serum levels of mmp-9 and the same subscale hamd scores ( core symptom , activity , psychic anxiety , somatic anxiety ) as observed with mmp-2 ( table 3 ) . a significant negative correlation between serum levels of mmp-2 and mmp-9 was observed in the md group ( p=.001 , rho=-0.479 ) , but not in the scz group ( p=.368 , rho=-0.184 ) or in the control group ( p=.592 , rho=0.087 ) ( figure 2c ) . correlation between serum levels of matrix metalloproteinases ( mmps ) and total hamilton rating scale for depression ( hamd ) score in patients with mood disorders ( md ) before and after a course of ect . ( a ) significant negative correlation between serum levels of mmp-2 and total hamd score . ( b ) pre - ect values (  ) and post - ect values (  ) ; n=21 , * p < .05 the clinical data of the 3 groups ( md , scz , and control ) are presented in table 1 . patients with md were significantly older and their duration of illness was shorter compared with the scz group . duration of current episode , number of ects , and duration of the ect course did not differ between the md and scz groups . there were no differences between the dose equivalence of imipramine of pre - ect and post - ect in the md group and also no differences between the dose equivalence of chlorpromazine of pre - ect and post - ect in the scz group . subject clinical data abbreviations : bprs , brief psychiatric rating scale ; cpz , chlorpromazine ; ect , electroconvulsive therapy ; hamd , hamilton rating score for depression ; imi , imipramine ; md , mood disorder ; scz : schizophrenia - spectrum disorder . comparison between scores at pre - ect and those at post - ect by wilcoxon signed - rank test . serum levels of mmp-2 in the md group with depressive episodes at pre - ect were significantly lower than those of the control group ( figure 1a ; p=.023 ) , whereas there were no significant differences for the serum levels of timp-2 , mmp-9 , and timp-1 between the md group and the control group ( figure 1b - d ) . serum levels of mmp-2 , mmp-9 , timp-1 , and timp-2 in the md group at pre - ect were not significant different compared with those of the scz group with psychotic episodes at pre - ect . additionally , serum levels of mmps and timps were not significantly different between md patients with either md ( unipolar ) or bipolar disorder ( bipolar ) at pre - ect ( mmp-2 , unipolar=165.925.0ng / ml vs bipolar=159.426.8ng / ml , p=.512 ; timp-2 , 63.17.6ng / ml vs 66.66.2ng / ml , p=.259 ; mmp-9 , 553.9218.8ng / ml vs 604.6310.5ng / ml , p=.668 ; timp-1 , 150.539.4ng / ml vs 148.023.2ng / ml , p=.571 ) . scatter plot of serum levels of matrix metalloproteinases ( mmps ) and tissue inhibitors of mmps ( timps ) . mmp-2 ( a ) , timp-2 ( b ) , mmp-9 ( c ) , and timp-1 ( d ) in controls (  ) , mood disorders ( md ) group before a course of ect ( pre - ect ,  ) and after a course of ect ( post - ect ,  ) , and schizophrenia - spectrum disorders ( scz ) group pre - ect (  ) and post - ect (  ) . the horizontal bars represent the mean values . in the roc curve analysis of diagnosis , the auc of mmp-2 , mmp-9 , timp-1 , and timp-2 at pre - ect between the md and control groups were 0.738 , 0.603 , 0.674 , and 0.675 , respectively . the scores for depressive symptoms evaluated by hamd in the md group and the scores of psychotic symptoms evaluated by bprs in the scz group significantly decreased following ect ( table 1 ) . there was a statistically significant increase in serum levels of mmp-2 in the md group over the course of ect ( p=.046 ) but no significant change observed in the scz group ( p=.650 ) ( figure 1a ) . there were statistically significant decreases in serum levels of mmp-9 in both the md and scz groups following ect ( md group , p=.003 ; scz group , p=.019 ) ( figure 1c ) . among the 2 nonresponders to ect in the scz group , one patient had an increase in serum level of mmp-9 and the other had a decrease in serum level of mmp-9 after the course of ect ( data not shown ) . serum levels of timp-2 and timp-1 did not significantly change over the course of ect in both the md and scz groups ( figure 1b , d ) . no significant correlations were observed in the md group between subject characteristics ( gender , age , age of onset , duration of illness , duration of current episode , or dose of medication ) and serum levels of mmp-2 , mmp-9 , timp-1 , and timp-2 at either pre - ect or post - ect ( data not shown ) . correlation coefficients were calculated between serum levels of mmps and timps and clinical symptomatic scores evaluated by hamd for md and by bprs for scz , combining results from pre - ect and post - ect ( table 2 ) . in the scz group , there was no significant correlation between serum levels of mmps , timps , and total bprs scores ( table 2 ) . in the md group , serum levels of timp-1 and timp-2 furthermore , no significant correlations were observed between timps and subscale hamd scores ( table 3 ) . correlation between mmp and timp serum levels and clinical symptomatic scores of md and scz groups abbreviations : bprs : brief psychiatric rating scale ; hamd , hamilton rating score for depression ; md , mood disorder ; mmp , matrix metalloproteinase ; scz , schizophrenia - spectrum disorder ; timp , tissue inhibitor of mmp . correlation between mmp and timp serum levels and subscale hamd scores in md groups abbreviations : hamd , hamilton rating score for depression ; md , mood disorder ; mmp , matrix metalloproteinase ; timp , tissue inhibitor of mmp . however , in the md group , there was a significant negative correlation between serum levels of mmp-2 and total hamd score ( p=.041 ) ( table 2 ; figure 2a ) and a significant positive correlation between serum levels of mmp-9 and total hamd score ( p=.006 ) ( table 2 ; figure 2b ) . furthermore , negative correlations between serum levels of mmp-2 and subscale hamd scores ( core symptom , activity , somatic anxiety ) were observed as well as positive correlations between serum levels of mmp-9 and the same subscale hamd scores ( core symptom , activity , psychic anxiety , somatic anxiety ) as observed with mmp-2 ( table 3 ) . a significant negative correlation between serum levels of mmp-2 and mmp-9 was observed in the md group ( p=.001 , rho=-0.479 ) , but not in the scz group ( p=.368 , rho=-0.184 ) or in the control group ( p=.592 , rho=0.087 ) ( figure 2c ) . correlation between serum levels of matrix metalloproteinases ( mmps ) and total hamilton rating scale for depression ( hamd ) score in patients with mood disorders ( md ) before and after a course of ect . ( a ) significant negative correlation between serum levels of mmp-2 and total hamd score . ( b ) pre - ect values (  ) and post - ect values (  ) ; n=21 , * p < .05 the current study demonstrated that serum levels of mmp-2 were specifically reduced in md patients with depressive symptoms applicable to ect and that serum levels of both mmp-2 and mmp-9 were significantly altered in opposing directions in a depressive state - dependent manner following ect . in addition , alterations of mmp-2 and mmp-9 appear to be associated with certain depressive symptoms such as not only core symptom , but also somatic anxiety and activity . the current study is the first to demonstrate a significant negative association between serum levels of mmp-2 and clinical scores of depressive symptoms during the course of ect in md patients . a previous proteomic study demonstrated that the plasma levels of mmp-2 in depressive patients were significantly lower than those of control subjects , and plasma levels of mmp-2 in schizophrenic patients were the same as those of control subjects ( domenici et al . , 2010 ) . the study , however , measured mmps at only one time point , utilized a proteomics method , and did not evaluate patient symptoms . despite these limitations , the previous findings parallel the current findings . it is currently unknown why circulating levels of mmp-2 declined and are associated with levels of mmp-9 in the md patients in a depressive state . mmp-2 is constitutively expressed in almost all human tissues , but mainly by endothelial and epithelial cells and fibroblasts ( sbardella et al . , astrocytes are a major source of mmp-2 and presumably drive physiological remodeling of the blood brain barrier ( bbb ) ( del zoppo et al . mmp-2 is detectable in significant serum concentrations under physiological conditions and is linked to homeostatic functioning ( sbardella et al . , 2012 ) . the current study showed a reduction of mmp-2 in md patients before ect and an increase in mmp-2 after a course of ect . a number of studies have demonstrated significant reductions of glia , mainly astrocytes , in the postmortem brain of md patients ( ongur et al . , 1998 ; cotter et al . , 2001 ; gittins and harrison , 2011 ) . another postmortem brain study demonstrated that coverage of blood vessels by astrocyte endfeet in the prefrontal cortex was significantly reduced in patients with md ( rybakowski et al . , 2013 ) . the decline in glia within brain vasculature areas associated with mood function suggests the possibility of reductions in microenvironmental cellular components of the bbb , which is composed of astrocytes and vascular endothelial cells , in md patients . a clinical finding pointed out that serum levels of mmp-2 were decreased in patients suffering from subarachnoid hemorrhage , in which the bbb is in fact compromised ( horstmann et al . , 2006 ) . decreased mmp-2 in the circulation in md patients , then , suggests a small compromise of the bbb compared with a gross compromise observed with subarachnoid hemorrhage . the increase of serum levels of mmp-2 in md patients after the ect course could be associated with the remodeling of gliovascular units , which is supported by previous ect findings showing gliogenesis and angiogenesis ( hellsten et al . , 2005 ; wennstrom et al . , 2006 ; bouckaert et al . , 2014 further , this mmp-2-related phenomenon could lead to increased incidences of inflammatory states such as production of mmp-9 through a disruption in the bbb in the brain of md patients , because expression of mmp-9 is regulated not only by immune cells in response to inflammatory events ( van den steen et al . , 2002 ; sbardella et al . , 2012 ) but also directly by mmp-2 activity ( dzwonek et al . , 2004 ; romi et al . , thus , future studies will be needed to clearly establish evidence of a mmp-2-related  dysregulated bbb  and concurrent alteration of mmp-9 in md patients by examining samples from patients such as postmortem brain and cerebrospinal fluid . in the current study , the serum levels of mmp-9 in md patients was not significantly different from that of the control group before ect , but mmp-9 significantly decreased following ect . similar to the current findings , a previous study found that hamd scores and serum levels of mmp-9 were positively correlated and there was no difference between depressed patients and controls in serum levels of mmp-9 ( yoshida et al . , 2012 ) . others , however , have found that plasma levels of mmp-9 in depressed patients were significantly higher than those of the controls in a proteomic study ( domenici et al . , 2010 ) , and serum levels of mmp-9 in depressed young patients with bipolar disorder were significantly higher than those of the controls , which remained elevated even following drug treatment ( rybakowski et al . , 2013 ) . possible reasons for the discrepancy between the current findings and the findings of increased mmp-9 in depressed patients include differences in subject age , severity of symptoms , choice of symptom rating scale , and treatment protocol . it is also possible that circulating mmp-9 is considerably sensitive to psychosocial stress even in healthy individuals ( garvin et al . , 2009 ) . an inflammatory state has been proposed as the substrate of md , since circulating proinflammatory cytokines increase with the severity of mood disturbance symptoms ( felger and lotrich , 2013 ; rosenblat et al . , it is possible that in a depressive episode , the homeostatic state maintained by the immune system could be altered by changes in expression of proinflammatory cytokines and mmps , and these alterations could be normalized through ect treatment . the decreased mmp-9 levels in both md and scz groups following ect could reflect a common involvement of mmp-9 in psychiatric disorders . fragile x syndrome , psychiatric disorders associated with anxiety , compulsive - repetitive behaviors , and social communication deficits have been associated with changes in mmp-9 levels . knockout of the mmp-9 gene improved symptoms in a mouse model of fragile x syndrome and reduced dendritic spine abnormalities ( sidhu et al . , 2014 ) . a clinical trial of the antibiotic minocycline decreased mmp-9 levels and appeared to attenuate the symptoms of fragile x syndrome ( dziembowska et al . , 2013 ) . these findings , combined with the current findings , suggest that decreasing mmp-9 alleviates some types of psychiatric disorders . as biomarkers for md , roc analysis in the current study demonstrated that the auc for both mmps and timps prior to ect was found to be 0.745 at its peak , which does not suggest that either ligand would have high diagnostic value as a biomarker . because serum levels of mmp-2 was negatively correlated to certain depressive symptoms , to which mmp-9 was positively correlated , both mmp-2 and mmp-9 could serve as biomarkers for specific depressive states or symptoms with greater accuracy if possibly combined with other inflammatory ligands such as cytokines . to place the current findings into perspective , there are a few limitations that should be mentioned . while the total sample size of the current study was small , significant correlations were nonetheless observed . second , it is unclear if blood concentrations of mmp and timp reflect those in the brain . there are some reports that found no correlation between blood and csf concentrations of mmps ( horstmann et al . , 2010 ; niebroj - dobosz et al . , therefore , it is possible that the dynamics of mmps , as well as timp , in the brain are different from those in peripheral tissues . to overcome this issue , direct assessment of mmps in csf from md patients could be highly useful . finally , the effect of medications on serum mmps levels is not well understood . although there were no statistically significantly differences before and after ect on the equivalence of both imipramine and chlorpromazine , patients were allowed to use medication during the course of ect . a future investigation could include drug - nave patients to evaluate the effects of medications on mmp , at least before treatments . serum levels of mmp-2 were significantly decreased in md patients with depressive episodes , and a course of ect in these patients significantly increased mmp-2 but decreased mmp-9 . also in md patients , there were significant correlations between depressive symptoms and serum levels of mmp-2 and mmp-9 , in opposite directions , in response to ect . the findings suggest that alteration of homeostasis linked to inflammation lead to changes in levels of mmp-2 and mmp-9 , which occurs in a disease - specific manner and depend on the severity of depressive symptoms , which are in turn sensitive to ect treatment . shigeto yamawaki md , phd has received donation for research from astellas , pfizer and msd honoraria for lectures from glaxo smith kline , astellas , daiichi sankyo , japan eli lilly , takeda , otsuka , eisai , dai nippon sumitomo , shionogi , meiji seika , mochida , and pfizer .