Risperidone Reduces Matrix Metalloproteinase-9 and Increases Neurotrophin-3 in Schizophrenia Spectrum of Disorder

Abstract

Even though earlier studies have reported alteration in the markers of synaptic plasticity (Matrix metalloproteinase-9 [MMP-9] and Neurotrophin-3 [NT-3]), there are no reports about the effect of risperidone on the same. The present study was designed to assess the effect of risperidone on NT-3 and MMP-9 levels in patients with schizophrenia spectrum of disorder and to investigate whether these markers can be used to predict the treatment response in these patients. 62 schizophrenia spectrum of disorder patients were enrolled in the study and were treated with 4 mg of risperidone OD. Serum NT-3 and MMP-9 levels were compared at baseline and after 6 weeks following risperidone treatment. Severity of the disease was assessed using Positive and Negative Syndrome Scale (PANSS). MMP-9 was significantly reduced and NT-3 was significantly increased in schizophrenia spectrum of disorder after treatment with risperidone. We also found a significant reduction in MMP-9 levels in the non-responders group. At a cut off of 1225 ng/mL, MMP-9 can predict response to treatment with 64% sensitivity and 62% specificity and at a cut off of 957 pg/mL, NT-3 predicted the response to treatment with 60% sensitivity and 62% specificity. We conclude that risperidone decreases the serum levels of MMP-9 and increases the NT-3 levels in schizophrenia spectrum of disorder. MMP-9 and NT-3 can predict the response to treatment with risperidone.

Introduction

Schizophrenia spectrum disorders are psychiatric disorders which includes Schizotypal disorder, Delusional disorder, Brief psychotic disorder, Schizophreniform disorder, Schizophrenia, Schizoaffective disorder [1]. Even though several hypotheses have been postulated in its pathophysiology, etiology of schizophrenia is not well understood, rendering it as a complex disorder [2]. Recent studies have hypothesized that deranged synaptic plasticity and altered inflammatory response may be contributing to the pathophysiology of schizophrenia [3, 4].

Synaptic plasticity is the ability of synapses to strengthen or weaken over time, in response to increase or decrease in their activity [5]. Matrix metalloproteinase dependent processing of the proteins like cell adhesion molecules is responsible for the normal functioning of synapse [6]. Among the members of MMP family, MMP-9 was found to have a significant role in brain neuronal development. MMP-9 was found to be responsible for the deranged synaptic plasticity resulting from abnormal neuronal morphology [7]. In a recent study from our laboratory, we demonstrated elevated MMP-9 levels in drug naïve schizophrenia patients [8]. Yamamori et al. have reported elevated MMP-9 levels in treatment resistant schizophrenia patients [9].

Neurotrophins are nerve growth factors responsible for the development and survival of the neurons [10]. Neurotropins aid in the mobilization and release of pre synaptic vesicles containing the neurotransmitter. Alterations in the level of Neurotropins and their receptors were reported to result in abnormal nerve impulse transmission across the synapse [11]. Neurotrophin-3 (NT-3), a member of neurotrophin family, was not extensively studied in schizophrenia. Durany et al. have demonstrated reduced NT-3 levels in post mortem brain samples when compared with controls [12]. Vargas et al. have shown reduced NT-3 levels in schizophrenia patients who were on medications and suggested that NT-3 levels might be related to the course of illness or to treatment variables [13]. A recent study by Keshri et al. have reported elevated NT-3 levels in schizophrenia cases compared to healthy controls [14].

Risperidone, a second-generation anti-psychotic drug is used for the treatment of schizophrenia. Even though MMP-9 and NT-3, are known to be involved in the pathogenesis of Schizophrenia spectrum of disorder, there are no studies till date to document whether these markers can be used to predict treatment response in schizophrenia patients. Hence this study was designed to assess the effect of risperidone on the serum levels of MMP-9 and NT-3, in schizophrenia.

Materials and Methods

Subjects

A longitudinal follow-up study was conducted from December 2015 to August 2017 in Department of Biochemistry, JIPMER, Puducherry, India. Approval for the study was obtained from the Institution Human Ethics Committee and a written informed consent was obtained from all the participants and their legally accepted representative. Sixty two participants, aged between 15 and 45 years, who are diagnosed as Schizophrenia spectrum of disorder as per DSM-5 (APA-13) and 62 age and gender matched controls were included in the study. Patients with known medical illness such as diabetes mellitus, cardiovascular disease, Liver disorders, Renal disorders, Inflammatory disorders, Patients with history of substance use, who were taking drugs like antiepileptics or psychotropics were excluded from the study. All the participants were treated with Risperidone tablets, 4 mg OD for 6 weeks.

Clinical Evaluation

Study subjects were assessed by a detailed clinical history and brief physical examination. Positive and Negative Syndrome Scale(PANSS), is a 30 item, clinician administered scale for assessing positive symptoms (delusion, hallucination), negative symptoms (withdrawal, amotivation, paucity of speech) and general psychopathology in cases with schizophrenia. Each item has 7 point scale, higher score means more severity of the symptoms, same applies to total score. This scale is used for assessing response to treatment. PANSS Score was done before and after 6 weeks of treatment with Risperidone. The study participants were divided into 2 groups. Participants with greater than or equal to 40% reduction in PANSS score after treatment with Risperidone from the baseline were grouped as Responders. Participants with less than 40% reduction in PANSS score were grouped as non-responders [15].

Sample Collection

Five ml of venous blood samples were obtained from the participants before the treatment and six weeks after treatment with Risperidone. Serum was separated and stored at  − 80°C and used for the analysis of NT-3 and MMP-9.

Biochemical Analysis

Commercially available ELISA kits were used to determine serum MMP-9 and NT-3 levels (Raybiotech, Mexico).

Statistical Analysis

Continuous data was represented as Mean and Standard deviation /Median and interquartile range depending upon its distribution. Categorical data was represented as proportion and percentage. Paired t test and Wilcoxson’s signed rank sum test was used to evaluate the changes in the biochemical parameters. Spearman test was used to assess the association of MMP-9 and NT-3 with PANSS score and duration of illness. ROC curve analysis was performed to identify the cut off value, specificity and sensitivity of MMP-9 and NT-3 in schizophrenia cases in response to treatment. Statistical analysis was performed using SPSS software 19.0 version and p value < 0.05 was considered as statistically significant.

Results

Table 1 shows the clinical characteristics and biochemical parameters in schizophrenia spectrum disorder and controls. At baseline assessment patients had significantly higher serum levels of MMP-9 and NT-3 compared to that in controls. Among 62 cases, we had 31 men and their duration of illness varied from one month to 20 years.

Table 1.

Age, clinical characteristics, biochemical parameters and PANSS in controls and schizophrenia spectrum of disorder patients

Parameters	Controls (n = 62)	Schizophrenia spectrum of Disorders (n = 62)
Age (Years)	38.7 ± 8	32.21 ± 8.86
Gender (M/F)	31/31	31/31
Duration of illness	–	2 years (1 month- 20 years)
Drug naïve / Drug free	–	37/25
Matrix Metalloproteinase–9 (µg/L)	555.1 (59–1167)	2309.5 (32–8382)*
Neurotropin–3 (ng/L)	109 (38–393)	542.2 (2–2532)*

*p < 0.001 compared to controls

Table 2 shows the clinical characteristics and the effect of Risperidone on MMP-9 and NT-3 in schizophrenia spectrum disorder. Among the cases, 37 (59.6%) were drug naïve and 25 (40%) were drug free for a minimum period of 6 weeks. After treatment with risperidone, NT-3 (p = 0.036) was significantly increased and MMP9 (p = 0.022) was significantly reduced. There was a significant decrease (p < 0.001) in the total score and the subclass of PANSS score after treatment with risperidone.

Table 2.

Age, clinical characteristics, biochemical parameters and PANSS in schizophrenia spectrum of disorder patients before and after treatment with Risperidone

Parameters	Before treatment (n = 62)	After treatment (n = 62)	p value
Matrix Metalloproteinase–9 (µg/L)	2309.5 (32–8382)	1048.76 (15–7224)	0.022
Neurotropin–3 (ng/L)	542.2 (2–2532)	849.7 (3–4467)	0.036
Positive symptom score	24.02 ± 5.57	13.55 ± 4.70	< 0.001
Negative symptom score	18.03 ± 5.68	12.48 ± 4.25	< 0.001
General psychopathology symptom score	38.50 ± 6.6	26.39 ± 6.74	< 0.001
Total symptom score	80.55 ± 15.03	52.42 ± 13.83	< 0.001

Table 3 shows the effect of Risperidone on the biochemical parameters and PANSS score among the responders and non responders. Following treatment with Risperidone, MMP-9 was significantly reduced (p = 0.017) in the non-responders group. In both, responder and non-responder groups, Total score and the subclass of PANSS score was significantly reduced after treatment with risperidone.

Table 3.

Effect of Risperidone on biochemical parameters and PANSS score among responders and non responders

Parameters	Responders (n = 25)			Non responders (n = 37)
	Before treatment	After treatment	p value	Before treatment	After treatment	p value
Neurotropin–3 (ng/L)	822.68 (1.86–1881.6)	1118.75 (4–3077)	0.135	429.7 (2.15–2532.47)	488.2 (2.85- 4467.4)	0.182
Metalloproteinase–9 (µg/L)	3694 (95–7608)	3556.7 (55–7224)	0.476	1322.80 (32–8382)	439.6 (14.75–6687.4)	0.017
Positive symptom score	24.60 ± 5.68	10.56 ± 2.23	< 0.001	23.62 ± 5.5	15.57 ± 4.81	< 0.001
Negative symptom score	20.08 ± 4.52	10.80 ± 2.94	< 0.001	16.65 ± 6.02	13.62 ± 4.65	< 0.001
General psychopathology symptom score	40.32 ± 5.43	22.3 ± 4.62	< 0.001	37.27 ± 7.10	29.11 ± 6.62	< 0.001
Total symptom score	85.00 ± 11.69	43.72 ± 7.08	< 0.001	77.54 ± 16.40	58.30 ± 14.24	< 0.001

Table 4 shows the association of pre-treatment and post-treatment levels of MMP-9 and NT-3 levels with PANSS score and duration of illness in schizophrenia cases. NT-3 was significantly associated with negative symptom score (r = 0.29, p = 0.022) before treatment and MMP-9 was negatively associated with general psychopathology score (r =  − 0.28, p = 0.03) after treatment in schizophrenia. We did not observe any association with duration of illness with MMP-9 and NT-3.

Table 4.

Association of Metalloproteinase–9 and Neurotropin–3 with duration of illness and disease severity scores in schizophrenia cases before and after treatment

Parameters	Metalloproteinase–9				Neurotropin–3
	Before Treatment		After Treatment		Before Treatment		After Treatment
	r	p	r	p	r	p	r	p
Neurotropin–3	0.550	0.001	0.445	0.001
Duration of illness	− 0.085	0.51	− 0.018	0.83	0.010	0.94	− 0.05	0.70
Positive symptom score	− 0.02	0.89	− 0.25	0.05	0.09	0.50	0.08	0.49
Negative symptom score	0.225	0.08	− 0.11	0.42	0.29	0.022*	0.15	0.25
General psychopathology symptom score	0.22	0.865	− 0.28	0.03*	0.17	0.18	0.12	0.34
Total symptom score	0.09	0.49	− 0.25	0.05	0.22	0.09	0.14	0.29

Figure 1 shows the ROC curve for MMP-9. It shows that at cut off of 1225 ng/mL, MMP-9 can predict response to treatment with 64% sensitivity and 62% specificity.

Fig. 1.

ROC curve for Metalloproteinase–9 for predicting treatment response to risperidone in schizophrenia spectrum disorder at 1225 μg/L (AUC–0.659, sensitivity of 64% and specificity of 62%)

Figure 2 shows the ROC curve for NT-3. It shows at cut off of 957 pg/mL, NT-3 can predict response to treatment with 60% sensitivity and 62% specificity.

Fig. 2.

ROC curve for Neurotropin–3 for predicting treatment response to risperidone in schizophrenia spectrum disorder at 957 ng/L (AUC–0.606, Sensitivity–60%, specificity–62%)

Discussion

In our study we tried to find the effect of 6 week of risperidone treatment on neurotropic biomarkers(MMP-9 and NT-3) in patients with schizophrenia spectrum disorders and based on the response we tried to find whether MMP-9 and NT-3 levels can predict the response to treatment with risperidone.

Patients showed significantly higher MMP-9 and NT-3 levels compared to that in age and gender matched controls at baseline prior to starting antipsychotic treatment. After 6 weeks of risperidone treatment, within the cases, there was significant change in psychopathology scores(decreased), in MMP-9 levels (decreased), and in NT-3 levels(increased) (Table 4). Significant decrease in MMP-9 levels at the end of 6 weeks was noticed only in the non-responders to risperidone treatment. Both MMP-9 and NT-3 showed significant correlation with psychopathology scores but no correlation with the duration of the illness.

Abnormality in the synaptic plasticity resulting from abnormal morphology of the dendritic spine was found to be associated with the alteration in the circulating levels of MMP-9 in several psychiatric disorders [7]. Previous investigators have demonstrated elevated MMP-9 levels in schizophrenia [8, 14]. However the data on the effect of risperidone on MMP-9 levels in schizophrenia was found to be limited. The results of the present study demonstrated a significant decrease (p=0.022) in the serum levels of MMP-9 in schizophrenia after treatment with Risperidone for 6 weeks compared to their baseline levels. When schizophrenia patients were divided into responders (> 40% reduction in PANSS) and non responders (< 40% reduction in PANSS), we observed that MMP-9 was significantly reduced in non responder group after treatment with respiridone.

Neurotropin-3 (NT3) is a neuroprotective protein that regulates neuronal survival, synaptic plasticity, and neurotransmission [16]. Previous studies have shown reduced expression of NT-3 in the postmortem brain tissue and CSF fluid when compared with controls [12, 17]. In the present study, NT-3 levels were significantly increased in schizophrenia cases compared to controls, which were similar to a recent study by Keshri et al [14]. These findings were in contrast to a previous study by Vargas et al [13] who had demonstrated reduction in NT-3 levels in schizophrenia patients on regular medications, whereas in our study we recruited drug naïve and drug free schizophrenia cases Also the sample size was more in our study and we included apparently healthy controls compared to earlier studies [12, 13]. To the best of our knowledge there are no previous studies about the effect of Risperidone on NT-3 levels in schizophrenia. In the present study there was a significant increase (p=0.036) in the serum NT-3 levels after treatment with risperidone for 6 weeks compared to their baseline levels. NT-3 levels did not show any association with response to treatment status at the end of 6 weeks.

Although the mechanism through which Risperidone decreases MMP-9 and increases NT-3 level in schizophrenia was not clear, our findings indicate that Risperidone aids in the remodeling of synapses in CNS by altering the level of these markers in the brain and thereby improving the synaptic plasticity.

When ROC curve analysis was done to identify whether these markers can predict the treatment response in schizophrenia patients, we found that at a cut off of 1225ng/mL, MMP-9 can predict response to treatment with 64% sensitivity and 62% specificity and at a cut off of 957pg/mL, NT-3 predicted the response to treatment with 60% sensitivity and 62% specificity.

The role of Risperidone in reducing the severity of schizophrenia spectrum has been well established in several studies [18]. In concurrence with other investigators, the data from our study reported a significant reduction in positive and negative symptoms after treatment with risperidone. Based on the findings from our study, we speculate that risperidone may reduce the severity of schizophrenia by altering inflammation and synaptic plasticity.

The current study had few limitations. The ideal follow up period to study the effect of risperidone on these markers would be at the end of 6 to 8 weeks with effective dose of risperidone being 2 mg to 16 mg per day. However, we tried with fixed dose of 4mg per day thereby not able to assess relationship between levels of neurotrophins with the dose and also the patients were not followed up to assess the disease severity after 6 weeks. In our present design we could not elucidate the mechanism through which risperidone alters the markers of inflammation and synaptic plasticity.

Further genetic studies are required to investigate whether risperidone can alter the mRNA expression of these markers in schizophrenia.

Conclusion

The data from the present study concludes that risperidone increases the circulatory levels of NT-3 and decreases the MMP9 levels. MMP-9 and NT-3 levels can be used as biomarkers to predict the response to treatment with risperidone.

Abbreviations

MMP

Matrix metalloproteinase

NT

Neurotrophin-3

PANSS

Positive and negative syndrome scale

DSM-5

Diagnostic and statistical manual of mental disorders, edition 5

ICD 10

International classification of diseases, tenth edition

Authors’ Contributions

RC Acquisition and analysis of data, HN the conception and design of the study, Analysis and interpretation of data, literature search, manuscript preparation, SK Design of the study, Interpretation of the data, manuscript review, ACG Statistical analysis, manuscript editing, DT: Acquisition and analysis of data.

Funding

This work was supported by a grant from JIPMER intramural fund sanctioned to the Corresponding author.

Data Availability

Available.

Declarations

Conflicts of interest

The authors declare that they have no conflicts of interest.

Ethics Approval

Institute ethics committee for human studies approved the study (JIP/IEC/2015/20/708).

Consent to Participate

Written informed consent was obtained from all the participants prior to the study.

Consent for Publication

All authors have given their consent for publication. Earlier presentation: Dr Raghavi C, presented a poster titled ‘Effect of respiridone on markers of inflammation and synaptic plasticity in schizophrenia spectrum disorders authored by Raghavi.C, Hanumanthappa Nandeesha, Shivanand Kattimani at ACBICON -2017 at Lucknow, Uttar Pradesh.