Nitric Oxide Synthase Inhibitors as Antidepressants

A comprehensive review on phosphatidylinositol-3-kinase (PI3K) and its inhibitors bearing pyrazole or indazole core for cancer therapy

Cancer is a complex and multifaceted group of diseases with a high mortality rate characterized by uncontrolled proliferation of abnormal cells. Dysregulation of normal signalling pathways in cancer contributes to the different hallmarks of this disease. The signalling pathway of which phosphatidylinositol 3-kinase (PI3K) is a part is not an exception. In fact, dysregulated activation of PI3K signalling pathways can result in unbridled cellular proliferation and enhanced cell survival, thereby fostering the onset and advancement of cancer. Therefore, there is substantial interest in developing targeted therapies specifically aimed at inhibiting the PI3K enzyme and its associated pathways. Also, the therapeutic interest on pyrazoles and indazoles has been growing due to their various medicinal properties, namely, anticancer activity. Derivatives of these compounds have been studied as PI3K inhibitors, and they showed promising results. There are already some PI3K inhibitors approved by Food and Drug Administration (FDA), such as Idelalisib (Zydelig®) and Alpelisib (Piqray®). In this context, this review aims to address the importance of PI3K in cellular processes and its role in cancer. Additionally, it aims to report a comprehensive literature review of PI3K inhibitors, containing the pyrazole and indazole scaffolds, published in the last fifteen years, focusing on structure-activity relationship aspects, thus providing important insights for the design of novel and more effective PI3K inhibitors.

Resocialization mitigates depressive behaviors induced by social isolation stress in mice: Attenuation of hippocampal neuroinflammation and nitrite level

BACKGROUND AND AIM

Social isolation stress (SIS) is a stressor known to trigger depressive behaviors. Psychiatric disorders are associated with neurobiological changes, such as neuroinflammation and an increase in nitric oxide (NO) signaling. Despite the well-established detrimental effects of SIS and the involvement of neuroinflammation and NO in depression, potential management strategies, especially resocialization, remain insufficiently explored. Our aim was to elucidate the effects of resocialization on depressive behaviors in socially isolated mice, with a focus on the possible involvement of neuroinflammation and nitrite in the hippocampus (HIP).

METHODS

We utilized 24 Naval Medical Research Institute male mice, maintained under both social and isolation conditions (SC and IC). After the isolation period, the mice were divided into two groups of eight, including the SIS group and a resocialized group. The SC group was kept without exposure to isolation stress. We conducted the open-field test, forced swimming test, and splash test to evaluate depressive behaviors. Additionally, nitrite levels, as well as the gene expression of interleukin (IL)-1β, tumor necrosis factor (TNF), and toll-like receptor 4 (TLR4) in the HIP, were measured.

RESULTS

The study found that resocialization significantly reduces depressive behaviors in SIS mice. The results suggest that the antidepressive effects of resocialization may be partially due to the modulation of the neuroinflammatory response and nitrite levels in the HIP. This is supported by the observed decrease in hippocampal gene expression of IL-1β, TLR4, and TNF, along with a reduction in nitrite levels following resocialization.

CONCLUSION

These insights could pave the way for new management strategies for depression, emphasizing the potential benefits of social interactions.

In Vitro Determination of Nitric Oxide Synthase Inhibition, Antioxidant Capacity and Phenolic Content of Various Natural Products (Bee and Herbal Products)

It is obvious that the oxidation process is an undeniable fact and when it comes to aging, one of the first solutions that come to mind is natural products. When it comes to natural products, both plants and bee products play an important, almost combative role against oxidation. For this purpose, natural products of both plant and animal origin were considered together in our study: Linden, green tea, aronia, wild grapes, myrtle, blueberries and basil, honey, pollen and propolis. Total phenolic content values of the extracts ranged between 49.28 and 3859.06 mg gallic acid equivalent/100 g, and propolis, green tea, chestnut flower and aronia samples were found to have the highest values. When looking at the NOS inhibition potential, it was determined that propolis, pollen and aronia samples had the highest percentage inhibition values of 98.11, 92.29, 83.44, respectively. Antioxidant activities of methanolic extracts were investigated using iron(III) reducing/antioxidant capacity (FRAP), 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity test and NOS inhibition tests. The phenolic composition of methanolic extracts was tested using the RP-HPLC-UV (high-performance liquid chromatographic method with ultraviolet) method with 19 phenolic standards.

Impaired coronary microvascular reactivity in youth with bipolar disorder

BACKGROUND

Cardiovascular disease (CVD) is excessively prevalent and premature in bipolar disorder (BD), even after controlling for traditional cardiovascular risk factors. The increased risk of CVD in BD may be subserved by microvascular dysfunction. We examined coronary microvascular function in relation to youth BD.

METHODS

Participants were 86 youth, ages 13-20 years (n = 39 BD, n = 47 controls). Coronary microvascular reactivity (CMVR) was assessed using quantitative T2 magnetic resonance imaging during a validated breathing-paradigm. Quantitative T2 maps were acquired at baseline, following 60-s of hyperventilation, and every 10-s thereafter during a 40-s breath-hold. Left ventricular structure and function were evaluated based on 12-15 short- and long-axis cardiac-gated cine images. A linear mixed-effects model that controlled for age, sex, and body mass index assessed for between-group differences in CMVR (time-by-group interaction).

RESULTS

The breathing-paradigm induced a significant time-related increase in T2 relaxation time for all participants (i.e. CMVR; β = 0.36, p < 0.001). CMVR was significantly lower in BD v. controls (β = -0.11, p = 0.002). Post-hoc analyses found lower T2 relaxation time in BD youth after 20-, 30-, and 40 s of breath-holding (d = 0.48, d = 0.72, d = 0.91, respectively; all pFDR < 0.01). Gross left ventricular structure and function (e.g. mass, ejection fraction) were within normal ranges and did not differ between groups.

CONCLUSION

Youth with BD showed evidence of subclinically impaired coronary microvascular function, despite normal gross cardiac structure and function. These results converge with prior findings in adults with major depressive disorder and post-traumatic stress disorder. Future studies integrating larger samples, prospective follow-up, and blood-based biomarkers are warranted.

A review of poly(ADP-ribose)polymerase-1 (PARP1) role and its inhibitors bearing pyrazole or indazole core for cancer therapy

Cancer is a disease with a high mortality rate characterized by uncontrolled proliferation of abnormal cells. The hallmarks of cancer evidence the acquired cells characteristics that promote the growth of malignant tumours, including genomic instability and mutations, the ability to evade cellular death and the capacity of sustaining proliferative signalization. Poly(ADP-ribose) polymerase-1 (PARP1) is a protein that plays key roles in cellular regulation, namely in DNA damage repair and cell survival. The inhibition of PARP1 promotes cellular death in cells with homologous recombination deficiency, and therefore, the interest in PARP protein has been rising as a target for anticancer therapies. There are already some PARP1 inhibitors approved by Food and Drug Administration (FDA), such as Olaparib and Niraparib. The last compound presents in its structure an indazole core. In fact, pyrazoles and indazoles have been raising interest due to their various medicinal properties, namely, anticancer activity. Derivatives of these compounds have been studied as inhibitors of PARP1 and presented promising results. Therefore, this review aims to address the importance of PARP1 in cell regulation and its role in cancer. Moreover, it intends to report a comprehensive literature review of PARP1 inhibitors, containing the pyrazole and indazole scaffolds, published in the last fifteen years, focusing on structure-activity relationship aspects, thus providing important insights for the design of novel and more effective PARP1 inhibitors.

Modulatory effect of olanzapine on neuronal nitric oxide synthase (nNOS) expression in the rat striatum

Nitric oxide (NO) has been thought to be a novel factor involved in the mechanisms of mental disorders pathogenesis for quite some time. However, little is known about potential crosstalk between neuronal NO signaling and neuroleptics action. The present work was, therefore, focused on gene expression of neuronal NO synthase (nNOS) in the brains of rats chronically treated with olanzapine, an atypical antipsychotic drug. Studies were carried out on adult, male Sprague-Dawley rats that were divided into 2 groups: control and experimental animals treated with olanzapine (28-day-long intraperitoneal injection, at dose 5 mg/kg daily). All individuals were killed under anesthesia and the whole brains excised. Immunohistochemical procedure was used for histological assessment of the whole brain, and for both descriptive and quantitative analysis of nNOS protein distribution in selected brain structures. Long-term treatment with olanzapine is reflected in different changes in the number of enzyme-expressing cells in the rat brain. Olanzapine decreased the number of nNOS-expressing cells and possibly reduced NO synthesis in the rat striatum. Olanzapine can be taken into account as a potential inhibitor of NO synthesis in the rat striatum.

Exploring the Roles of Vitamins C and D and Etifoxine in Combination with Citalopram in Depression/Anxiety Model: A Focus on ICAM-1, SIRT1 and Nitric Oxide

The study of intercellular adhesion molecule-1 (ICAM-1) and SIRT1, a member of the sirtuin family with nitric oxide (NO), is emerging in depression and anxiety. As with all antidepressants, the efficacy is delayed and inconsistent. Ascorbic acid (AA) and vitamin D (D) showed antidepressant properties, while etifoxine (Etx), a GABAA agonist, alleviates anxiety symptoms. The present study aimed to investigate the potential augmentation of citalopram using AA, D and Etx and related the antidepressant effect to brain and serum ICAM-1, SIRT1 and NO in an animal model. BALB/c mice were divided into naive, control, citalopram, citalopram + etx, citalopram + AA, citalopram + D and citalopram + etx + AA + D for 7 days. On the 8th day, the mice were restrained for 8 h, followed by a forced swim test and marble burying test before scarification. Whole-brain and serum expression of ICAM-1, Sirt1 and NO were determined. Citalopram's antidepressant and sedative effects were potentiated by ascorbic acid, vitamin D and etifoxine alone and in combination (p < 0.05), as shown by the decreased floating time and rearing frequency. Brain NO increased significantly (p < 0.05) in depression and anxiety and was associated with an ICAM-1 increase versus naive (p < 0.05) and a Sirt1 decrease (p < 0.05) versus naive. Both ICAM-1 and Sirt1 were modulated by antidepressants through a non-NO-dependent pathway. Serum NO expression was unrelated to serum ICAM-1 and Sirt1. Brain ICAM-1, Sirt1 and NO are implicated in depression and are modulated by antidepressants.

Unraveling the Potential of Isorhamnetin as an Adjuvant in Depression Treatment with Escitalopram

Oxidative stress and inflammation are implicated in depression. While selective serotonin reuptake inhibitors (SSRIs) like escitalopram are commonly prescribed as first-line treatments, their inconsistent efficacy and delayed onset of action necessitates the exploration of adjunctive therapies. Isorhamnetin, a flavonol, has shown antioxidant and anti-inflammatory properties that makes exploring its antidepressant effect attractive. This study aims to investigate the adjuvant potential of isorhamnetin in combination with escitalopram to enhance its antidepressant efficacy in a lipopolysaccharide (LPS)-induced depression model using Swiss albino mice. Behavioral paradigms, such as the forced swim test and open field test, were employed to assess depressive symptoms, locomotion, and sedation. Additionally, enzyme-linked immunosorbent assays were utilized to measure Nrf2, BDNF, HO-1, NO, and IL-6 levels in the prefrontal cortex and hippocampus. The results demonstrate that isorhamnetin significantly improves the antidepressant response of escitalopram, as evidenced by reduced floating time in the forced swim test. Moreover, isorhamnetin enhanced antidepressant effects of escitalopram and effectively restored depleted levels of Nrf2, BDNF, and HO-1 in the cortex caused by LPS-induced depression. Isorhamnetin shows promise in enhancing the efficacy of conventional antidepressant therapy through antioxidant and anti-inflammatory effects.

Regulation of pleiotropic physiological roles of nitric oxide signaling

Nitric Oxide (NO) is a highly diffusible, ubiquitous signaling molecule and a free radical that is naturally synthesized by our body. The pleiotropic effects of NO in biological systems are due to its reactivity with different molecules, such as molecular oxygen (O₂), superoxide anion, DNA, lipids, and proteins. There are several contradictory findings in the literature pertaining to its role in oncology. NO is a Janus-faced molecule shown to have both tumor promoting and tumoricidal effects, which depend on its concentration, duration of exposure, and location. A high concentration is shown to have cytotoxic effects by triggering apoptosis, and at a low concentration, NO promotes angiogenesis, metastasis, and tumor progression. Upregulated NO synthesis has been implicated as a causal factor in several pathophysiological conditions including cancer. This dichotomous effect makes it highly challenging to discover its true potential in cancer biology. Understanding the mechanisms by which NO acts in different cancers helps to develop NO based therapeutic strategies for cancer treatment. This review addresses the physiological role of this molecule, with a focus on its bimodal action in various types of cancers.

Nitric Oxide Synthase inhibition counteracts the stress-induced DNA methyltransferase 3b expression in the hippocampus of rats

It has been postulated that the activation of NMDA receptors (NMDAr) and nitric oxide (NO) production in the hippocampus is involved in the behavioral consequences of stress. Stress triggers NMDAr-induced calcium influx in limbic areas, such as the hippocampus, which in turn activates neuronal NO synthase (nNOS). Inhibition of nNOS or NMDAr activity can prevent stress-induced effects in animal models, but the molecular mechanisms behind this effect are still unclear. In this study, cultured hippocampal neurons treated with NMDA or dexamethasone showed an increased of DNA methyltransferase 3b (DNMT3b) mRNA expression, which was blocked by pre-treatment with nNOS inhibitor nω -propyl-l-arginine (NPA). In rats submitted to the Learned Helplessness paradigm (LH), we observed that inescapable stress increased DNMT3b mRNA expression at 1h and 24h in the hippocampus. The NOS inhibitors 7-NI and aminoguanidine (AMG) decreased the number of escape failures in LH and counteracted the changes in hippocampal DNMT3b mRNA induced in this behavioral paradigm. Altogether, our data suggest that NO produced in response to NMDAr activation following stress upregulates DNMT3b in the hippocampus.

Arsenic alters nitric oxide signaling similar to autism spectrum disorder and Alzheimer's disease-associated mutations

Epidemiological studies have proven that exposure to Arsenic (AS) leads to the development of many neurological disorders. However, few studies have investigated its molecular mechanisms in the brain. Our previous work has revealed nitric oxide (NO)-mediated apoptosis and SNO reprogramming in the cortex following arsenic treatment, yet the role of NO and S-nitrosylation (SNO) in AS-mediated neurotoxicity has not been investigated. Therefore, we have conducted a multidisciplinary in-vivo study in mice with two different doses of Sodium Arsenite (SA) (0.1 ppm and 1 ppm) in drinking water. We used the novel SNOTRAP-based mass spectrometry method followed by the bioinformatics analysis, Western blot validation, and five different behavioral tests. Bioinformatics analysis of SA-treated mice showed significant SNO-enrichment of processes involved in mitochondrial respiratory function, endogenous antioxidant systems, transcriptional regulation, cytoskeleton maintenance, and regulation of apoptosis. Western blotting showed increased levels of cleaved PARP-1 and cleaved caspase-3 in SA-treated mice consistent with SA-induced apoptosis. Behavioral studies showed significant cognitive dysfunctions similar to those of Autism spectrum disorder (ASD) and Alzheimer's disease (AD). A comparative analysis of the SNO-proteome of SA-treated mice with two transgenic mouse strains, models of ASD and AD, showed molecular convergence of SA environmental neurotoxicity and the genetic mutations causing ASD and AD. This is the first study to show the effects of AS on SNO-signaling in the striatum and hippocampus and its effects on behavioral characteristics. Finally, further investigation of the NO-dependent mechanisms of AS-mediated neurotoxicity may reveal new drug targets for its prevention.

Hydrogen Ion Dynamics as the Fundamental Link between Neurodegenerative Diseases and Cancer: Its Application to the Therapeutics of Neurodegenerative Diseases with Special Emphasis on Multiple Sclerosis

The pH-related metabolic paradigm has rapidly grown in cancer research and treatment. In this contribution, this recent oncological perspective has been laterally assessed for the first time in order to integrate neurodegeneration within the energetics of the cancer acid-base conceptual frame. At all levels of study (molecular, biochemical, metabolic, and clinical), the intimate nature of both processes appears to consist of opposite mechanisms occurring at the far ends of a physiopathological intracellular pH/extracellular pH (pHi/pHe) spectrum. This wide-ranging original approach now permits an increase in our understanding of these opposite processes, cancer and neurodegeneration, and, as a consequence, allows us to propose new avenues of treatment based upon the intracellular and microenvironmental hydrogen ion dynamics regulating and deregulating the biochemistry and metabolism of both cancer and neural cells. Under the same perspective, the etiopathogenesis and special characteristics of multiple sclerosis (MS) is an excellent model for the study of neurodegenerative diseases and, utilizing this pioneering approach, we find that MS appears to be a metabolic disease even before an autoimmune one. Furthermore, within this paradigm, several important aspects of MS, from mitochondrial failure to microbiota functional abnormalities, are analyzed in depth. Finally, and for the first time, a new and integrated model of treatment for MS can now be advanced.

Environmental Exposures and Congenital Heart Disease

Congenital heart disease (CHD) is the most common congenital abnormality worldwide, affecting 8 to 12 infants per 1000 births globally and causing >40% of prenatal deaths. However, its causes remain mainly unknown, with only up to 15% of CHD cases having a determined genetic cause. Exploring the complex relationship between genetics and environmental exposures is key in understanding the multifactorial nature of the development of CHD. Multiple population-level association studies have been conducted on maternal environmental exposures and their association with CHD, including evaluating the effect of maternal disease, medication exposure, environmental pollution, and tobacco and alcohol use on the incidence of CHD. However, these studies have been done in a siloed manner, with few examining the interplay between multiple environmental exposures. Here, we broadly and qualitatively review the current literature on maternal and paternal prenatal exposures and their association with CHD. We propose using the framework of the emerging field of the exposome, the environmental complement to the genome, to review all internal and external prenatal environmental exposures and identify potentiating or alleviating synergy between exposures. Finally, we propose mechanistic pathways through which susceptibility to development of CHD may be induced via the totality of prenatal environmental exposures, including the interplay between placental and cardiac development and the internal vasculature and placental morphology in early stages of pregnancy.

Nitric Oxide Synthase activity in major depressive episodes before and after antidepressant treatment: Results of a large case-control treatment study

BACKGROUND

Nitric oxide synthase (NOS) activity, an enzyme potentially involved in the major depressive episodes (MDE), could be indirectly measured by the L-Citrulline/L-Arginine ratio (L-Cit/L-Arg). The aim of this study was: (1) to compare the NOS activity of patients with a MDE to that of healthy controls (HC); (2) to assess its change after antidepressant treatment.

METHODS

A total of 460 patients with a current MDE in a context of major depressive disorder (MDD) were compared to 895 HC for NOS activity (L-Cit/L-Arg plasma ratio). L-Arg and L-Cit plasma levels were measured using a MS-based liquid chromatography method. Depressed patients were assessed at baseline, and after 3 and 6 months of antidepressant treatment for depression severity and clinical response.

RESULTS

Depressed patients had a lower NOS activity than HC at baseline [0.31 ± 0.09 v. 0.38 ± 0.12; 95% confidence interval (CI) -0.084 to -0.062, p < 0.0001]. Lower NOS activity at baseline predicted a higher response rate [odds ratio (OR) = 29.20; 95% CI 1.58-536.37; p = 0.023]. NOS activity in depressed patients increased significantly up to 0.34 ± 0.08 after antidepressant treatment (Est = 0.0034; 95% CI 0.0002-0.0067; p = 0.03).

CONCLUSIONS

Depressed patients have a decreased NOS activity that improves after antidepressant treatment and predicts drug response. NOS activity may be a promising biomarker for MDE in a context of MDD.

Possible involvement of NO-sGC-cGMP signaling in the antidepressant like effect of pyridoxine in mice

The present study was designed to determine the antidepressant like effect of pyridoxine in mice. Pyridoxine (12.5, 25 and 50 mg/kg, i.p.) was administered to the mice and depression related behavioral and neurochemical alterations were determined. It was observed that pyridoxine (50 mg/kg, i.p.) treatment decreased the immobility period in tail suspension test (TST) and forced swim test (FST) significantly as compared to control. Pyridoxine (50 mg/kg, i.p.) treatment increased the level of serotonin (5-HT) and decreased the level of nitrite in the brain of mice significantly as compared to control. Pyridoxine thus confer antidepressant like effect by increasing the level of 5-HT and by decreasing the level of nitrite in the brain of mice. Further the influence of nitric oxide (NO)/ soluble guanylate cyclase (sGC)/ cyclic guanosine monophosphate (cGMP) in antidepressant-like effect of pyridoxine was studied. It was observed that the pretreatment of NO donor (i.e. L-Arginine) and cGMP modulator (i.e. sildenafil) counteracted while the pretreatment of NO/sGC inhibitor (i.e. methylene blue) potentiated the effect of pyridoxine in TST and FST. Pretreatment of NO donor did not influence, pretreatment of NO/sGC inhibitor decreased while the pretreatment of cGMP modulator increased the level of brain nitrite in pyridoxine treated mice. Further the pretreatment of NO donor and cGMP modulator decreased while the pretreatment of NO/sGC inhibitor increased the level of brain serotonin in pyridoxine treated mice. Pyridoxine thus exerted antidepressant like effect and NO-sGC-cGMP signaling modulated the antidepressant like effect of pyridoxine in mice.

Anti-depressant Effect of Betaine Mediates via Nitrergic and Serotoninergic Systems in Ovariectomized Mice

This study aimed to determine the anti-depressant effect of betaine (BT) in ovariectomized mice and its possible interaction with nitrergic and serotoninergic systems. In experiment 1, the mice were divided into control and sham groups, ovariectomy (OVX), OVX+BT (12.5mg/kg), OVX+BT (25 mg/kg), and OVX+BT (50mg/kg) groups. In experiment 2, the mice were assigned into control and sham, OVX, OVX+BT (50mg/kg), OVX+L-NAME (10 mg/kg), as well as OVX+injection of the BT and L-NAME. Experiments 3-5 were similar to experiment 2, except for L-Arginine (50 mg/kg), Fluoxetine (5 mg/kg), and Cyproheptadine (4 mg/kg) that were injected instead of the L-NAME. Subsequently, forced swimming test (FST), tail suspension test (TST), and open field test (OFT) were performed in this study. Moreover, this study determined serum Malondialdehyde (MDA), Superoxide dismutase (SOD), Glutathione peroxidase (GPx), and total antioxidant status levels. According to the findings, OVX increased immobility time, compared to the control group (P<0.05). In addition, BT (50mg/kg) decreased depression-induced immobility time, compared to the OVX group (P<0.05). The co-injection of the BT+L-NAME decreased depression-induced immobility time in TST and FST, followed by an increase in the number of crossing in OFT(P<0.05).Moreover, the co-injection of the BT+L-Arginine significantly diminished the antidepressant activity of BT on immobility time and decreased positive effect of BT on the number of crossing (P<0.05). The co-injection of the BT+Fluoxetine significantly amplified the antidepressant activity of BT on immobility time and number of crossing (P<0.05). Furthermore, the co-injection of the BT+Cyproheptadine decreased antidepressant activity of BT on immobility time and number of crossing (P<0.05). The BT (25 and 50mg/kg) reduced the MDA; however, it elevated SOD and GPx levels in OVX mice (P<0.05). It seems that antidepressant activity of BT mediates via nitrergic and serotoninergic systems in OVX mice.

Antidepressant Like Effect of Ascorbic Acid in Mice: Possible Involvement of NO-sGC-cGMP Signaling

The present study was designed to determine the antidepressant like activity of ascorbic acid (AA) in mice. Further the influence of NO-sGC-cGMP signaling in the antidepressant like effect of AA in mice was determined. Male swiss albino mice were used in the present study. Mice in the control group received saline and fluoxetine (10 mg/kg, i.p.) was used as the standard antidepressant drug. AA (50, 100 and 150 mg/kg, i.p.) was administered to the mice and depression related behavior were determined using tail suspension test (TST) and forced swim test (FST). Further the whole brain nitrite and serotonin levels were also determined. It was observed that the administration of AA (100 mg/kg, i.p.) reversed the depression like behavior in mice in TST and FST. AA (100 mg/kg, i.p.) treatment decreased the level of nitrite and increased the level of serotonin in the brain of mice significantly as compared to control. Further the behavioral and neurochemical effect of AA (50 mg/kg, i.p) was studied in NO modulator [NO donor: L-Arginine (50 mg/kg, i.p); NO-sGC inhibitor: methylene blue (1 mg/kg, i.p.) and cGMP modulator: sildenafil (1 mg/kg, i.p.)] pretreated mice. It was observed that the pretreatment of NO donor and cGMP modulator counteracted the effect conferred by AA (50 mg/kg, i.p). While the pretreatment of NO-sGC inhibitor potentiated the effect conferred by AA (50 mg/kg, i.p). The present study suggested that the AA confer antidepressant like effect in mice and NO-sGC-cGMP signaling pathway influence the antidepressant like effect of AA in mice.

The role of brain gaseous neurotransmitters in anxiety

Although anxiety is perhaps one of the most significant current medical and social problems, the neurochemical mechanistic background of this common condition remains to be fully understood. Multifunctional regulatory gasotransmitters are novel, atypical inorganic factors of the brain that are involved in the mechanisms of anxiety responses. Nitric oxide (NO) signaling shows ambiguous action in animal models of anxiety, while NO donors exert anxiogenic or anxiolytic effect depending on their chemical structure, dose, treatment schedule and gas release rapidity. The majority of NO synthase inhibitors act as a relatively potent axiolytic agents, while hydrogen sulfide (H₂S) and carbon monoxide (CO) delivered experimentally in the form of "slow" or "fast" releasing donors have recently been considered as anxiolytic neurotransmitters. In this comprehensive review we critically summarize the literature regarding the intriguing roles of NO, H₂S and CO in the neuromolecular mechanisms of anxiety in the context of their putative, yet promising therapeutic application. A possible mechanism of gasotransmitter action at the level of anxiety-related synaptic transmission is also presented. Brain gasesous neuromediators urgently require further wide ranging studies to clarify their potential value for the current neuropharmacology of anxiety disorders.

Alterations in acylcarnitines, amines, and lipids inform about the mechanism of action of citalopram/escitalopram in major depression

Selective serotonin reuptake inhibitors (SSRIs) are the first-line treatment for major depressive disorder (MDD), yet their mechanisms of action are not fully understood and their therapeutic benefit varies among individuals. We used a targeted metabolomics approach utilizing a panel of 180 metabolites to gain insights into mechanisms of action and response to citalopram/escitalopram. Plasma samples from 136 participants with MDD enrolled into the Mayo Pharmacogenomics Research Network Antidepressant Medication Pharmacogenomic Study (PGRN-AMPS) were profiled at baseline and after 8 weeks of treatment. After treatment, we saw increased levels of short-chain acylcarnitines and decreased levels of medium-chain and long-chain acylcarnitines, suggesting an SSRI effect on β-oxidation and mitochondrial function. Amines-including arginine, proline, and methionine sulfoxide-were upregulated while serotonin and sarcosine were downregulated, suggesting an SSRI effect on urea cycle, one-carbon metabolism, and serotonin uptake. Eighteen lipids within the phosphatidylcholine (PC aa and ae) classes were upregulated. Changes in several lipid and amine levels correlated with changes in 17-item Hamilton Rating Scale for Depression scores (HRSD₁₇). Differences in metabolic profiles at baseline and post-treatment were noted between participants who remitted (HRSD₁₇≤ 7) and those who gained no meaningful benefits (<30% reduction in HRSD₁₇). Remitters exhibited (a) higher baseline levels of C3, C5, alpha-aminoadipic acid, sarcosine, and serotonin; and (b) higher week-8 levels of PC aa C34:1, PC aa C34:2, PC aa C36:2, and PC aa C36:4. These findings suggest that mitochondrial energetics-including acylcarnitine metabolism, transport, and its link to β-oxidation-and lipid membrane remodeling may play roles in SSRI treatment response.

Plasma Metabolomics Profiling of Metabolic Pathways Affected by Major Depressive Disorder

Background: Major depressive disorder (MDD) is a common disease which is complicated by metabolic disorder. Although MDD has been studied relatively intensively, its metabolism is yet to be elucidated. Methods: To profile the global pathophysiological processes of MDD patients, we used metabolomics to identify differential metabolites and applied a new database Metabolite set enrichment analysis (MSEA) to discover dysfunctions of metabolic pathways of this disease. Hydrophilic metabolomics were applied to identify metabolites by profiling the plasma from 55 MDD patients and 100 sex-, gender-, BMI-matched healthy controls. The metabolites were then analyzed in MSEA in an attempt to discover different metabolic pathways. To investigate dysregulated pathways, we further divided MDD patients into two cohorts: (1) MDD patients with anxiety symptoms and (2) MDD patients without anxiety symptoms. Results: Metabolites which were hit in those pathways correlated with depressive and anxiety symptoms. Altogether, 17 metabolic pathways were enriched in MDD patients, and 23 metabolites were hit in those pathways. Three metabolic pathways were enriched in MDD patients without anxiety, including glycine and serine metabolism, arginine and proline metabolism, and phenylalanine and tyrosine metabolism. In addition, L-glutamic acid was positively correlated with the severity of depression and retardation if hit in MDD patients without anxiety symptoms. Conclusions: Different kinds of metabolic pathophysiological processes were found in MDD patients. Disorder of glycine and serine metabolism was observed in both MDD patients with anxiety and those without.

Paroxetine binding and activation of phosphofructokinase implicates energy metabolism in antidepressant mode of action

Selective serotonin reuptake inhibitors (SSRIs) are the predominant drugs prescribed for Major Depressive Disorder. The immediate pharmacological target of SSRIs is the serotonin transporter. However, the delayed therapeutic effect and high rate of patient non-response make it highly likely that SSRIs also have other molecular targets that are yet to be identified. Cellular thermal shift assay (CETSA) is a method based on thermal stabilization of target proteins upon drug binding. In the present study, we show that the SSRI paroxetine binds to phosphofructokinase (PFK) protein using CETSA. We found that mouse brain PFK and recombinant human PFK proteins are stabilized by paroxetine incubation. Chronic paroxetine treatment also significantly increased mouse brain PFK thermal stability. Paroxetine significantly elevated in vitro and in vivo PFK activity. Levels of several metabolites in glutamate- and energy metabolism-related pathways are significantly correlated with PFK activity in mouse hippocampus. Our data show that paroxetine can bind to PFK and affect its activity. Implications of these results for the antidepressant mode of action of paroxetine are discussed.

Early-Life Stress Induces Depression-Like Behavior and Synaptic-Plasticity Changes in a Maternal Separation Rat Model: Gender Difference and Metabolomics Study

More than 300 million people suffer from depressive disorders globally. People under early-life stress (ELS) are reportedly vulnerable to depression in their adulthood, and synaptic plasticity can be the molecular mechanism underlying such depression. Herein, we simulated ELS by using a maternal separation (MS) model and evaluated the behavior of Sprague-Dawley (SD) rats in adulthood through behavioral examination, including sucrose preference, forced swimming, and open-field tests. The behavior tests showed that SD rats in the MS group were more susceptible to depression- and anxiety-like behaviors than did the non-MS (NMS) group. Nissl staining analysis indicated a significant reduction in the number of neurons at the prefrontal cortex and hippocampus, including the CA1, CA2, CA3, and DG regions of SD rats in the MS group. Immunohistochemistry results showed that the percentages of synaptophysin-positive area in the prefrontal cortex and hippocampus (including the CA1, CA2, CA3, and DG regions) slice of the MS group significantly decreased compared with those of the NMS group. Western blot analysis was used to assess synaptic-plasticity protein markers, including postsynaptic density 95, synaptophysin, and growth-associated binding protein 43 protein expression in the cortex and hippocampus. Results showed that the expression levels of these three proteins in the MS group were significantly lower than those in the NMS group. LC-MS/MS analysis revealed no significant differences in the peak areas of sex hormones and their metabolites, including estradiol, testosterone, androstenedione, estrone, estriol, and 5β-dihydrotestosterone. Through the application of nontargeted metabolomics to the overall analysis of differential metabolites, pathway-enrichment results showed the importance of arginine and proline metabolism; pantothenate and CoA biosyntheses; glutathione metabolism; and the phenylalanine, tyrosine, and tryptophan biosynthesis pathways. In summary, the MS model caused adult SD rats to be susceptible to depression, which may regulate synaptic plasticity through arginine and proline metabolism; pantothenate and CoA biosyntheses; glutathione metabolism; and phenylalanine, tyrosine, and tryptophan biosyntheses.

Curcumin in Depression: Potential Mechanisms of Action and Current Evidence-A Narrative Review

Major depressive disorder (MDD) is one of the most prevalent and debilitating disorders. Current available treatments are somehow limited, so alternative therapeutic approaches targeting different biological pathways are being investigated to improve treatment outcomes. Curcumin is the main active component in the spice turmeric that has been used for centuries in Ayurvedic medicine to treat a variety of conditions, including anxiety and depressive disorders. In the past decades, curcumin has drawn researchers' attention and displays a broad range of properties that seem relevant to depression pathophysiology. In this review, we break down the potential mechanisms of action of curcumin with emphasis on the diverse systems that can be disrupted in MDD. Curcumin has displayed, in a number of studies, a potency in modulating neurotransmitter concentrations, inflammatory pathways, excitotoxicity, neuroplasticity, hypothalamic-pituitary-adrenal disturbances, insulin resistance, oxidative and nitrosative stress, and endocannabinoid system, all of which can be involved in MDD pathophysiology. To date, a handful of clinical trials have been published and suggest a benefit of curcumin in MDD. With evidence that is progressively growing, curcumin appears as a promising alternative option in the management of MDD.

Repeated Nitrous Oxide Exposure Exerts Antidepressant-Like Effects Through Neuronal Nitric Oxide Synthase Activation in the Medial Prefrontal Cortex

Clinical studies have demonstrated that exposure to the inhalational general anesthetic nitrous oxide (N₂O) produces antidepressant effects in depressed patients. However, the mechanisms underlying the antidepressant effects of N₂O remain largely unknown. Neuronal nitric oxide synthase (nNOS)-mediated nitric oxide (NO) synthesis is essential for brain function and underlies the molecular mechanisms of many neuromodulators. We hypothesized that activation of the nNOS/NO pathway in the medial prefrontal cortex (mPFC) might mediate the antidepressant effects of N₂O. In this study, we revealed that repeated N₂O exposure produced antidepressant-like responses in mice. Our mechanistic exploration showed that repeated N₂O exposure increased burst firing activity and that the expression levels of BDNF with nNOS activation were dependent in the mPFC. In particular, the antidepressant-like effects of N₂O were also antagonized by local nNOS inhibition in the mPFC. In summary, our results indicated that N₂O exposure enhances BDNF expression levels and burst firing rates in an nNOS activation dependent manner, which might underlie the pharmacological mechanism of the antidepressant-like effects of N₂O exposure. The present study appears to provide further mechanistic evidence supporting the antidepressant effects of N₂O.

Distribution of neuronal nitric oxide synthase immunoreactivity in adult male Sprague-Dawley rat brain

Neuronal NOS (nNOS) accounts for most of the NO production in the nervous system that modulates synaptic transmission and neuroplasticity. Although previous studies have selectively described the localisation of nNOS in specific brain regions, a comprehensive distribution profile of nNOS in the brain is lacking. Here we provided a detailed morphological characterization on the rostro-caudal distribution of neurons and fibres exhibiting positive nNOS-immunoreactivity in adult Sprague-Dawley rat brain. Our results demonstrated that neurons and fibres in the brain regions that exhibited high nNOS immunoreactivity include the olfactory-related areas, intermediate endopiriform nucleus, Islands of Calleja, subfornical organ, ventral lateral geniculate nucleus, parafascicular thalamic nucleus, superior colliculus, lateral terminal nucleus, pedunculopontine tegmental nucleus, periaqueductal gray, dorsal raphe nucleus, supragenual nucleus, nucleus of the trapezoid body, and the cerebellum. Moderate nNOS immunoreactivity was detected in the cerebral cortex, caudate putamen, hippocampus, thalamus, hypothalamus, amygdala, and the spinal cord. Finally, low NOS immunoreactivity were found in the corpus callosum, fornix, globus pallidus, anterior commissure, and the dorsal hippocampal commissure. In conclusion, this study provides a comprehensive view of the morphology and localisation of nNOS immunoreactivity in the brain that would contribute to a better understanding of the role played by nNOS in the brain.

Additive interaction between scopolamine and nitric oxide agents on immobility in the forced swim test but not exploratory activity in the hole-board

RATIONALE

The muscarinic cholinergic antagonist scopolamine has received an attention due to its unique antidepressant effects. However, the considerable adverse effects on nervous system limit the use of scopolamine as a psychiatric drug.

OBJECTIVE

In order to overcome the limitations and increase the therapeutic effects of scopolamine, we decided to examine the effects of joint administration of sub-effective dose of scopolamine and the sub-effective dose of a nitric oxide (NO) precursor L-Arginine or a non-selective nitric oxide synthase (NOS) inhibitor L-NAME on depression- and anxiety-related behaviors in male NMRI mice.

METHODS

To this aim, animal behavior was assessed in the forced swim test (FST) and hole-board apparatus.

RESULTS

Scopolamine (0.05 mg/kg) significantly decreased immobility time in the FST, suggesting an antidepressant-like effect. Moreover, L-Arginine (50 mg/kg) produced an antidepressant-like response in the FST and decreased head-dip counts in the hole-board apparatus, indicating an anxiety-like effect. The same doses of scopolamine and L-Arginine decreased the locomotor activity in mice. Joint administration of sub-effective dose of scopolamine (0.01 mg/kg) with a low dose of L-Arginine (25 mg/kg) or L-NAME (1 mg/kg) induced a profound antidepressant-like effect in the FST. These drug combinations did not influence on anxiety-related behaviors. Meanwhile, L-NAME alone did not alter the performance of mice in the FST and hole-board. Isobolographic analysis revealed an additive effect for scopolamine and L-Arginine or L-NAME.

CONCLUSION

Data suggests that NO agents could positively impact the therapeutic profile of scopolamine, because they might be useful for inducing antidepressant-like effect associated to scopolamine.

Prelimbic neuronal nitric oxide synthase inhibition exerts antidepressant-like effects independently of BDNF signalling cascades

OBJECTIVES

NMDA antagonists and nitric oxide synthase (NOS) inhibitors induce antidepressant-like effects and may represent treatment options for depression. The behavioural effects of NMDA antagonists seem to depend on Tyrosine kinase B receptor (TrkB) activation by BDNF and on mechanistic target of rapamycin (mTOR), in the medial prefrontal cortex (mPFC). However, it is unknown whether similar mechanisms are involved in the behavioural effects of NOS inhibitors. Therefore, this work aimed at determining the role of TrkB and mTOR signalling in the prelimbic area of the ventral mPFC (vmPFC-PL) in the antidepressant-like effect of NOS inhibitors.

METHODS

Pharmacological treatment with LY235959 or ketamine (NMDA antagonists), NPA or 7-NI (NOS inhibitors), BDNF, K252a (Trk antagonist) and rapamycin (mTOR inhibitor) injected systemically or into vmPFC-PL followed by behavioural assessment.

RESULTS

We found that bilateral injection of BDNF into the vmPFC-PL induced an antidepressant-like effect, which was blocked by pretreatment with K252a and rapamycin. Microinjection of LY 235959 into the vmPFC-PL induced antidepressant-like effect that was suppressed by local rapamycin but not by K252a pretreatment. Microinjection of NPA induced an antidepressant-like effect insensitive to both K252a and rapamycin. Similarly, the antidepressant-like effects of a systemic injection of ketamine or 7-NI were not affected by blockade of mTOR or Trk receptors in the vmPFC-PL.

CONCLUSION

Our data support the hypothesis that NMDA blockade induces an antidepressant-like effect that requires mTOR but not Trk signalling into the vmPFC-PL. The antidepressant-like effect induced by local NOS inhibition is independent on both Trk and mTOR signalling in the vmPFC-PL.

The nitrergic neurotransmission contributes to the anxiolytic-like effect of Citrus sinensis essential oil in animal models

Citrus fragrances have been used in aromatherapy for the treatment of anxiety, and the essential oil of Citrus sinensis (sweet orange) has shown promising results, although its mechanism of action was not known. The objective of this study was to evaluate the involvement of nitric oxide (NO) neurotransmission in the anxiolytic-like effect of C. sinensis essential oil. Swiss male mice were submitted to 15 min of C. sinensis essential oil inhalation (1%, 2.5%, 5%, and 10%) and tested in the marble-burying test, neophobia-induced hypophagia, and light/dark test. Locomotor activity was evaluated in an automated locomotor activity box. The coadministration of C. sinensis essential oil with L-arginine (200 mg/kg, i.p.), an NO precursor, was used for the behavioral evaluation of nitrergic system mediation. Additionally, the NO synthase activity was measured by nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) analysis in the cerebral cortex. C. sinensis essential oil exerted anxiolytic-like effect at dose that did not change locomotor activity. Moreover, L-arginine pretreatment prevented this anxiolytic-like effect on marble-burying test. Finally, C. sinensis essential oil reduced the NADPH-d positive cells. Thus, the nitrergic neurotransmission plays a relevant role in the anxiolytic-like effect C. sinensis essential oil.

Nitric oxide signalling and antidepressant action revisited

Studies about the pathogenesis of mood disorders have consistently shown that multiple factors, including genetic and environmental, play a crucial role on their development and neurobiology. Multiple pathological theories have been proposed, of which several ultimately affects or is a consequence of dysfunction in brain neuroplasticity and homeostatic mechanisms. However, current clinical available pharmacological intervention, which is predominantly monoamine-based, suffers from a partial and lacking response even after weeks of continuous treatment. These issues raise the need for better understanding of aetiologies and brain abnormalities in depression, as well as developing novel treatment strategies. Nitric oxide (NO) is a gaseous unconventional neurotransmitter, which regulates and governs several important physiological functions in the central nervous system, including processes, which can be associated with the development of mood disorders. This review will present general aspects of the NO system in depression, highlighting potential targets that may be utilized and further explored as novel therapeutic targets in the future pharmacotherapy of depression. In particular, the review will link the importance of neuroplasticity mechanisms governed by NO to a possible molecular basis for the antidepressant effects.

Methylene Blue Analogues with Marginal Monoamine Oxidase Inhibition Retain Antidepressant-like Activity

Methylene blue (MB) possesses diverse medical applications. Among these, MB presents with antidepressant-like effects in animals and has shown promise in clinical trials for the treatment of mood disorders. As an antidepressant, MB may act via various mechanisms which include modulation of the nitric oxide cyclic guanosine monophosphate (NO-cGMP) cascade, enhancement of mitochondrial respiration and antioxidant effects. MB is also, however, a high potency inhibitor of monoamine oxidase (MAO) A, which most likely contributes to its antidepressant effect, but also to its adverse effects profile (e.g., serotonin toxicity). The latter has raised the question whether it is possible to design out the MAO inhibition properties of MB yet retaining its clinically useful attributes. This study explores this idea further by characterizing five newly synthesized low MAO-A active MB analogues and examining their antidepressant-like properties in the acute forced swim test (FST) in rats, with comparison to imipramine and MB. The results show that all five analogues exhibit antidepressant-like properties in the FST without confounding effects on locomotor activity. The magnitude of these effects is comparable to those of imipramine and MB. Moreover, these newly synthesized MB analogues are markedly less potent MAO-A inhibitors (IC₅₀ = 0.518-4.73 μM) than MB (IC₅₀ = 0.07 μM). We postulate that such lower potency MAO-A inhibitors may present with a reduced risk of adverse effects associated with MAO-A inhibition. While low level MAO-A inhibition still may produce an antidepressant effect, we posit that other MB-related mechanisms may underlie their antidepressant effects, thereby representing a novel group of antidepressant compounds.

Neuronal nitric oxide synthase and affective disorders

Affective disorders including major depressive disorder (MDD), bipolar disorder (BPD), and general anxiety affect more than 10% of population in the world. Notably, neuronal nitric oxide synthase (nNOS), a downstream signal molecule of N-methyl-D-aspartate receptors (NMDARs) activation, is abundant in many regions of the brain such as the prefrontal cortex (PFC), hippocampus, amygdala, dorsal raphe nucleus (DRN), locus coeruleus (LC), and hypothalamus, which are closely associated with the pathophysiology of affective disorders. Decreased levels of the neurotransmitters including 5-hydroxytryptamine or serotonin (5-HT), noradrenalin (NA), and dopamine (DA) as well as hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis are common pathological changes of MDD, BPD, and anxiety. Increasing data suggests that nNOS in the hippocampus play a crucial role in the etiology of MDD whereas nNOS-related dysregulation of the nitrergic system in the LC is closely associated with the pathogenesis of BPD. Moreover, hippocampal nNOS is implicated in the role of serotonin receptor 1 A (5-HTR1 A) in modulating anxiety behaviors. Augment of nNOS and its carboxy-terminal PDZ ligand (CAPON) complex mediate stress-induced anxiety and disrupting the nNOS-CAPON interaction by small molecular drug generates anxiolytic effect. To date, however, the function of nNOS in affective disorders is not well reviewed. Here, we summarize works about nNOS and its signal mechanisms implicated in the pathophysiology of affective disorders. On the basis of this review, it is suggested that future research should more fully focus on the role of nNOS in the pathomechanism and treatment of affective disorders.

Plasma metabolomic profiling of a ketamine and placebo crossover trial of major depressive disorder and healthy control subjects

(R,S)-Ketamine produces rapid, robust, and sustained antidepressant effects in major depressive disorder. Specifically, its pharmacological efficacy in treatment refractory depression is considered a major breakthrough in the field. However, the mechanism of action of ketamine's rapid effect remains to be determined. In order to identify pathways that are responsible for ketamine's effect, a targeted metabolomic approach was carried out using a double-blind, placebo-controlled crossover design, with infusion order randomized with medication-free patients with treatment-resistant major depressive disorder (29 subjects) and healthy controls (25 subjects). The metabolomic profile of these subjects was characterized at multiple time points, and a comprehensive analysis was investigated between the following: MDD and healthy controls, treatment and placebo in both groups and the corresponding response to ketamine treatment. Ketamine treatment resulted in a general increase in circulating sphingomyelins, levels which were not correlated with response. Ketamine response resulted in more pronounced effects in the kynurenine pathway and the arginine pathway at 4 h post-infusion, where a larger decrease in circulating kynurenine levels and a larger increase in the bioavailability of arginine were observed in responders to ketamine treatment, suggesting possible mechanisms for response to ketamine treatment.

Inflammation and depression: a causal or coincidental link to the pathophysiology?

This review summarises the evidence that chronic low grade inflammation triggers changes that contribute to the mental and physical ill health of patients with major depression. Inflammation, and the activation of the hypothalamic pituitary axis by stress, are normal components of the stress response but when stress is prolonged and the endocrine and immune system become chronic resulting in the activation of the peripheral macrophages, the central microglia and hypercortisolemia, the neuronal networks are damaged and become dysfunctional. The proinflammatory cytokines, in addition to activating the hypothalamic-pituitary-adrenal axis and thereby increasing cortisol synthesis, also activate the tryptophan-kynurenine pathway. This results in the synthesis of the neurotoxic N-methyl-d-aspartate (NMDA) glutamate agonist quinolinic acid and 3-hydroxykynurenine thereby enhancing oxidative stress and contributes to neurodegeneration which characterise major depression particularly in late life.While antidepressants attenuate some of the endocrine and immune changes caused by inflammation, not all therapeutically effective antidepressants do so. This suggests that drugs which specifically target the immune, endocrine and neurotransmitter systems may be more effective antidepressants.The preliminary clinical evidence that some non-steroidal anti-inflammatory drugs, such as the cyclooxygenase 2 inhibitor celecoxib, can enhance the response to standard antidepressant treatment is therefore considered and a critical assessment made of the possible limitations of such an approach to novel antidepressant development.

Methylene blue and its analogues as antidepressant compounds

Methylene Blue (MB) is considered to have diverse medical applications and is a well-described treatment for methemoglobinemias and ifosfamide-induced encephalopathy. In recent years the focus has shifted to MB as an antimalarial agent and as a potential treatment for neurodegenerative disorders such as Alzheimer's disease. Of interest are reports that MB possesses antidepressant and anxiolytic activity in pre-clinical models and has shown promise in clinical trials for schizophrenia and bipolar disorder. MB is a noteworthy inhibitor of monoamine oxidase A (MAO-A), which is a well-established target for antidepressant action. MB is also recognized as a non-selective inhibitor of nitric oxide synthase (NOS) and guanylate cyclase. Dysfunction of the nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) cascade is strongly linked to the neurobiology of mood, anxiety and psychosis, while the inhibition of NOS and/or guanylate cyclase has been associated with an antidepressant response. This action of MB may contribute significantly to its psychotropic activity. However, these disorders are also characterised by mitochondrial dysfunction and redox imbalance. By acting as an alternative electron acceptor/donor MB restores mitochondrial function, improves neuronal energy production and inhibits the formation of superoxide, effects that also may contribute to its therapeutic activity. Using MB in depression co-morbid with neurodegenerative disorders, like Alzheimer's and Parkinson's disease, also represents a particularly relevant strategy. By considering their physicochemical and pharmacokinetic properties, analogues of MB may provide therapeutic potential as novel multi-target strategies in the treatment of depression. In addition, low MAO-A active analogues may provide equal or improved response with a lower risk of adverse effects.

ZL006, a small molecule inhibitor of PSD-95/nNOS interaction, does not induce antidepressant-like effects in two genetically predisposed rat models of depression and control animals

N-methyl-D-aspartate receptor (NMDA-R) antagonists and nitric oxide inhibitors have shown promising efficacy in depression but commonly induce adverse events. To circumvent these, a more indirect disruption of the nitric oxide synthase/postsynaptic density protein 95 kDa complex at the NMDA-R has been proposed. This disruption can be achieved using small molecule inhibitors such as ZL006, which has attracted attention as ischemic stroke therapy in rodents and has been proposed as a potential novel treatment for depression. Based on this, our aim was to translate these findings to animal models of depression to elucidate antidepressant-like properties in more detail. In the present study, we administered ZL006 to two established animal models of depression and control rodents. Following treatment, we measured locomotion in the Open Field and depressive-like behavior in the Forced Swim Test and Tail Suspension Test. Our experimental designs included the use of different species (rats, mice), strains (Flinders Sensitive Line rats, Flinders Resistant Line rats, Wistar Kyoto rats, Wistar Hanover rats, Sprague Dawley rats, B6NTac mice), routes of administration (intraperitoneal, intracerebroventricular), times of administration (single injection, repeated injections), treatment regimens (acute, sustained), and doses (5, 10, 15, 50 mg/kg). ZL006 did not affect behavior in any of the described settings. On a molecular level, ZL006 significantly reduced total nitrate/nitrite concentrations in the cerebellum, supporting that it is capable of reducing nitric oxide metabolites in the brain. Future studies using different experimental parameters are needed to further investigate the behavioral profile of ZL006.

Adjuvant neuronal nitric oxide synthase inhibition for combined treatment of epilepsy and comorbid depression

BACKGROUND

Elevated nitric oxide (NO) levels in the brain have been apparently associated with depression in kindled animals. Owing to the major role of neuronal nitric oxide synthase (nNOS) in brain and ineffectiveness of antiepileptic drugs (AEDs) in restoring nitrosative stress, the present study was envisaged to evaluate the adjuvant nNOS inhibitor, 7-nitroindazole (7-NI) with valproic acid for combined treatment of epilepsy and associated depression.

METHODS

Pentylenetetrazole kindled animals associated with depression were treated with vehicle, valproate (300mg/kg/day ip), valproate with 7-NI (10mg/kg; 20mg/kg; 40mg/kg)/day ip and 7-NI (40mg/kg/day ip) for 15days. Except naïve, all groups were challenged with pentylenetetrazole (35mg/kg ip) on days 5, 10, and 15 to evaluate seizure severity. Depression was evaluated in all experimental groups using the tail suspension and forced swim test on days 1, 5, 10 and 15. On day 15, biochemical (corticosterone levels) and neurochemical (serotonin, kynurenine, tryptophan, glutamate, GABA, nitrite levels) estimations were carried out in cortical and hippocampal area of mice brain.

RESULTS

Vehicle treated kindled animals were significantly associated with depression. Chronic valproate treatment in kindled animals significantly reduced seizure severity, but could not reverse associated depression. 7-NI per se treatment in kindled animals was also reported unable to restore the associated depression completely. However, 7-NI supplementation with valproate significantly reduced seizure severity score and completely ameliorated depression with restoration of altered biochemical and neurochemical milieu.

CONCLUSION

Adjuvant nNOS inhibition can be previewed as safe therapy with AEDs for the combined management of epilepsy and associated depression.

Adjuvant indoleamine 2,3-dioxygenase enzyme inhibition for comprehensive management of epilepsy and comorbid depression

Epilepsy is one of the major neurological disorders frequently associated with psychiatric disorders such as depression. Alteration of tryptophan metabolism towards kynurenine pathway may be one of the plausible reasons for association of depression in epilepsy. Hence, this study was envisaged to evaluate the dose dependent inhibition of indoleamine 2,3-dioxygenase (IDO) enzyme (responsible for shifting tryptophan metabolism) employing minocycline with valproic acid for comprehensive management of epilepsy and comorbid depression. Kindling was induced in male swiss albino mice by administration of pentylenetetrazole subconvulsive dose (35mg/kg, i.p.) at an interval of 48±2h. Kindled animals were treated with saline, valproate (300mg/kg/day i.p.), valproate in combination with different doses of minocycline (10mg/kg; 20mg/kg; 40mg/kg)/day i.p. and minocycline per se (40mg/kg/day i.p.) for 15 days. Except naïve, all the groups were challenged with pentylenetetrazole (35mg/kg i.p.) on day 5, 10, and 15 to evaluate the seizure severity score. Depression was evaluated in all experimental groups using tail suspension and forced swim test on days 1, 5, 10 and 15, 2h after pentylenetetrazole challenge. Results suggested that saline treated kindled animals were significantly associated with depression. Chronic valproate treatment significantly reduced seizure severity score but unable to ameliorate the associated depression. Minocycline supplementation with valproic acid dose dependently ameliorated depression associated with epilepsy. Neurochemical and biochemical findings also supported the behavioural findings of the study. Thus, our results suggested that supplementation of IDO enzyme inhibitors with valproic acid could be explored further for comprehensive management of epilepsy and associated depression.

Pharmacological targeting of redox regulation systems as new therapeutic approach for psychiatric disorders: A literature overview

Redox dysregulation occurs following a disequilibrium between reactive oxygen species (ROS) producing and degrading systems, i.e. mitochondria, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases and nitric oxide synthase (NOS) on one hand and the principal antioxidant system, the glutathione, on the other hand. Increasing recent evidence points towards a pathogenetic role of an altered redox state in the development of several mental disorders, such as anxiety, bipolar disorders, depression, psychosis, autism and post-traumaticstress disorders (PTSD). In this regard, pharmacological targeting of the redox state regulating systems in the brain has been proposed as an innovative and promising therapeutic approach for the treatment of these mental diseases. This review will summarize current knowledge obtained from both pre-clinical and clinical studies in order to descant "lights and shadows" of targeting pharmacologically both the producing and degrading reactive oxygen species (ROS) systems in psychiatric disorders.

Behavioral despair associated with a mouse model of Crohn's disease: Role of nitric oxide pathway

Crohn's disease (CD) is associated with increased psychiatric co-morbidities. Nitric oxide (NO) is implicated in inflammation and tissue injury in CD, and it may also play a central role in pathogenesis of the accompanying behavioral despair. This study investigated the role of the NO pathway in behavioral despair associated with a mouse model of CD. Colitis was induced by intrarectal (i.r.) injection of 2,4,6-trinitrobenzenesulfonic acid (10mg TNBS in 50% ethanol). Forced swimming test (FST), pharmacological studies and tissues collection were performed 72 h following TNBS administration. To address a possible inflammatory origin for the behavioral despair following colitis induction, tumor necrosis factor-alpha (TNF-α) level was measured in both the hippocampal and colonic tissue samples. In parallel, hippocampal inducible nitric oxide synthase (iNOS) and nitrite level were evaluated. Pharmacological studies targeting the NO pathway were performed 30-60 min before behavioral test. Colitis was confirmed by increased colonic TNF-α level and microscopic score. Colitic mice demonstrated a significantly higher immobility time in the FST associated to a significant increase of hippocampal TNF-α, iNOS expression and nitrite content. Acute NOS inhibition using either Nω-nitro-l-arginine methyl ester (a non-specific NOS inhibitor) or aminoguanidine hydrochloride (a specific iNOS inhibitor) decreased the immobility time in colitic groups. Moreover, acute treatment with both NOS inhibitors decreased the TNF-α level and nitrite content in the hippocampal samples. This study suggests that the NO pathway may be involved in the behavioral effects in the mouse TNBS model of CD. These findings endow new insights into the gut-brain communication during the development of colonic inflammation, which may ultimately lead to improved therapeutic strategies to combat behavior changes associated with gastrointestinal disorders.