Monoamine Oxidase A Expression Research Articles

Abstract 2011: MAOA Drives Anti Androgen Therapy Resistance in Advanced Prostate Cancer by Conferring Neuroendocrine Plasticity via a Twist1 BRN2 Signaling Pathway

Abstract Background: Therapy resistance in cancer is often linked to cancer cell state or lineage changes. In prostate cancer (PCa), a subset of castration-resistant prostate cancer (CRPC) loses reliance on the androgen receptor (AR) signaling and gains neuroendocrine (NE) traits through a lineage switch along disease progression. However, the molecular mechanisms driving such cellular lineage plasticity remain unclear. This study investigated the functional and mechanistic role of monoamine oxidase A (MAOA) in driving adenocarcinoma (adeno)-to-NE lineage conversion in CRPC cells upon enzalutamide (ENZ), a FDA-approved newer-generation antiandrogen drug, and evaluated the efficacy of MAOA inhibitors for treating CRPC and overcoming ENZ resistance.Methods: ENZ-resistant C4-2B and CWR-R1 cells (C4-2BENZR and CWR-R1ENZR) CRPC cells were transfected with a PSA promoter-driven GFP expression construct for isolating a PSAlo/− cell population distinct from PSAhi cells, which was used for manipulation of MAOA expression levels and subsequent functional assays in vitro and in vivo. The MAOA expression levels were determined and correlated with NE parameters in PCa clinical samples by immunohistochemistry and data mining of multiple publicly available clinical datasets. Results: MAOA protein expression was significantly upregulated in the PSAlo/− ENZ-resistant cell population, accompanied by concomitant activation of NE markers and downregulation of luminal markers including AR and AR targets, compared to the PSAhi counterpart. Elevated MAOA expression was also found in PCa patient samples associated with NE features from multiple independent cohorts. Silencing MAOA suppressed the proliferation, migration, invasion, stem-like properties and NE plasticity of both PSAlo/- C4-2BENZR and CWR-R1ENZR cells. Moreover, co-culturing adeno LNCaP or C4-2B cells with MAOA-silenced PSAlo/- cells exhibiting a repressed secretory phenotype attenuated acquired induction of NE markers and proliferation of adeno cells as compared to controls. Mechanistically, MAOA induces Twist1, which directly activates the transcription and expression of BRN2, a master neural transcription factor known to confer NE differentiation and anti-AR therapy resistance in CRPC. Further, pharmacological inhibition of MAOA greatly enhanced the growth-inhibitory efficacy of ENZ with ENZ sensitivity restored in ENZ-resistant LuCaP PC PDX-derived organoids as well as a PSAlo/− CWR-R1ENZR xenograft mouse model.Conclusion: Our results suggest MAOA as a potential therapeutic target for reversing ENZ resistance in CRPC treatment by blockade of NE transdifferentiation.Funding Acknowledgements: This work was supported by the NIH/NCI grants R37CA233658 and R01CA258634 (to B. Wu) and the DOD Department of Defense EIRA award W81XWH-21-1-0218 (to J. Wei) Citation Format: Jing Wei, Jing Wang, Chia-hui Chen, Wen Guan, Boyang Wu. MAOA Drives Anti Androgen Therapy Resistance in Advanced Prostate Cancer by Conferring Neuroendocrine Plasticity via a Twist1 BRN2 Signaling Pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2011.

Melatonin attenuates fentanyl - induced behavioral sensitization and circadian rhythm disorders in mice

Melatonin is a neurohormone synthesized by the pineal gland to regulate the circadian rhythms and has proven to be effective in treating drug addiction and dependence. However, the effects of melatonin to modulate the drug-seeking behavior of fentanyl and its underlying molecular mechanism is elusive. This study was designed to investigate the effects of melatonin on fentanyl - induced behavioral sensitization and circadian rhythm disorders in mice. The accompanying changes in the expression of Brain and Muscle Arnt-Like (BMAL1), tyrosine hydroxylase (TH), and monoamine oxidase A (MAO-A) in relevant brain regions including the suprachiasmatic nucleus (SCN), nucleus accumbens (NAc), prefrontal cortex (PFC), and hippocampus (Hip) were investigated by western blot assays to dissect the mechanism by which melatonin modulates fentanyl - induced behavioral sensitization and circadian rhythm disorders. The present study suggest that fentanyl (0.05, 0.1 and 0.2 mg/kg) could induce behavioral sensitization and melatonin (30.0 mg/kg) could attenuate the behavioral sensitization and circadian rhythm disorders in mice. Fentanyl treatment reduced the expression of BMAL1 and MAO-A and increased that of TH in relevant brain regions. Furthermore, melatonin treatment could reverse the expression levels of BMAL1, MAO-A, and TH. In conclusion, our study demonstrate for the first time that melatonin has therapeutic potential for fentanyl addiction.

Size, Surface Properties, and Ion Release of Zinc Oxide Nanoparticles: Effects on Cytotoxicity, Dopaminergic Gene Expression, and Acetylcholinesterase Inhibition in Neuronal PC-12 Cells.

The extensive applications of zinc oxidenanoparticles (ZnO NPs) have resulted in a substantial risk of human exposure. However, the knowledge of the toxicity of these NPs in the nervous system is still limited. A comparative analysis of ZnO NPs of various sizes and NPs of the same size, with and without surface coating, and the potential role of released zinc ions is yet to be thoroughly explored. As a result, we have studied the cellular toxicity of two different-sized ZnO NPs, ZnO-22 (22nm) and ZnO-43 (43nm), and NPs with similar size but with polyvinylpyrrolidone coating (ZnO-P, 45nm). The findings from our study suggested a time-, size-, and surface coating-dependent cytotoxicity in PC-12 cells at a concentration ≥ 10μg/ml. ZnO NP treatment significantly elevated reactive oxygen and reactive nitrogen species, thereby increasing oxidative stress. The exposure of ZnO-22 and ZnO-43 significantly upregulated the expression of monoamine oxidase-A and downregulated the α-synuclein gene expression associated with the dopaminergic system. The interaction of NPs enzymes in the nervous system is also hazardous. Therefore, the inhibition activity of acetylcholinesterase enzyme was also studied for its interaction with these NPs, and the results indicated a dose-dependent inhibition of enzyme activity. Particle size, coating, and cellular interactions modulate ZnO NP's cytotoxicity; smaller sizes enhance cellular uptake and reactivity, while coating reduces cytotoxicity by limiting direct cell contact and potentially mitigating oxidative stress. Furthermore, the study of released zinc ions from the NPs suggested no significant contribution to the observed cytotoxicity compared to the NPs.

Glucose, Insulin and Oxygen Modulate Expression of Serotonin-Regulating Genes in Human First-Trimester Trophoblast Cell Line ACH-3P.

Serotonin signaling plays an important role in regulating development and functions of the placenta. We hypothesized that metabolic disturbances associated with maternal obesity and/or gestational diabetes mellitus (GDM) affect placental serotonin homeostasis. Therefore, we examined the effects of high glucose (25 mM) and insulin (10 nM)-two hallmarks of maternal obesity and GDM-on mRNA expression of key regulators of serotonin homeostasis, including serotonin transporter (SERT), tryptophan hydroxylase 1 (TPH1), and monoamine oxidase A (MAOA), in the first-trimester trophoblast cell line ACH-3P, focusing on oxygen levels characteristic of early human placental development. Glucose downregulated expression of SERT and MAOA independently of oxygen level and upregulated expression of TPH1 at 6.5% oxygen but not at 2.5% oxygen. Compared to 6.5% oxygen, 2.5% oxygen upregulated SERT and downregulated TPH1 expression, with no effect on MAOA expression. Insulin upregulated SERT only at 2.5% oxygen but had no effect on TPH1 and MAOA expression. These results suggest that maternal metabolic alterations in early pregnancy may be a driving force for changes in placental serotonin homeostasis.

Association of two variable number of tandem repeats in the monoamine oxidase A gene promoter with suicide completion: The present study and meta-analysis.

One potential cause of suicide is serotonergic dysfunction. Sex differences have been reported to modulate the effects of serotonergic polymorphisms. Monoamine oxidase A (MAOA) is an enzyme that degrades serotonin and is located on the X chromosome. A previous study indicated that the upstream (u) variable number of tandem repeat (VNTR) in the MAOA gene promoter may be associated with suicide. However, a meta-analysis showed that this polymorphism may not be related to suicide. According to a recent study, compared with the uVNTR, the distal (d)VNTR and the haplotypes of the two VNTRs modulate MAOA expression. We examined the two VNTRs in the MAOA gene promoter in 1007 subjects who committed suicide and 844 healthy controls. We analyzed the two VNTRs using fluorescence-based polymerase chain reaction assays. We conducted a meta-analysis for the two VNTRs to update it. Our results demonstrated that neither the genotype-based associations nor allele/haplotype frequencies of the two VNTRs were significantly associated with suicide. In the meta-analysis, we did not indicate relationships between uVNTR and suicide nor did we identify articles analyzing dVNTR in suicide. Overall, we did not find a relationship between the two VNTRs in the MAOA promoter and suicide completion; thus, warranting further studies are required.

Myocardial ischemia-reperfusion injury is probably due to the excessive production of mitochondrial ROS caused by the activation of 5-HT degradation system mediated by PAF receptor.

Previously, we revealed a crucial role of 5-HT degradation system (5DS), consisting of 5-HT2A receptor (5-HT2AR), 5-HT synthases and monoamine oxidase A (MAO-A), in ischemia-reperfusion (IR)-caused organ injury. Whereas, platelet activating factor receptor (PAFR) also mediates myocardial ischemia-reperfusion injury (MIRI). Here, we try to clarify the relationship between 5DS and PAFR in mediating MIRI. H9c2 cell injury and rat MIRI were caused by hypoxia/reoxygenation (H/R) or PAF, and by ligating the left anterior descending coronary artery then untying, respectively. 5-HT2AR and PAFR antagonists [sarpogrelate hydrochloride (SH) and BN52021], MAO-A, AKT, mTOR and 5-HT synthase inhibitors (clorgyline, perifosine, rapamycin and carbidopa), and gene-silencing PKCε were used in experiments RESULTS: The mitochondrial ROS production, respiratory chain damage, inflammation, apoptosis and myocardial infarction were significantly prevented by BN52021, SH and clorgyline in H/R and PAF-treated cells and in IR myocardium. BN52021 also significantly suppressed the upregulation of PAFR, 5-HT2AR, 5-HT synthases and MAO-A expression (mRNA and protein), and Gαq and PKCε (in plasmalemma) expression induced by H/R, PAF or IR; the effects of SH were similar to that of BN52021 except for no affecting the expression of PAFR and 5-HT2AR. Gene-silencing PKCε suppressed H/R and PAF-induced upregulation of 5-HT synthases and MAO-A expression in cells; perifosine and rapamycin had not such effects; however, clorgyline suppressed H/R and PAF-induced phosphorylation of AKT and mTOR. MIRI is probably due to PAFR-mediated 5-HT2AR activation, which further activates PKCε-mediated 5-HT synthesis and degradation, leading to mitochondrial ROS production.

Profile of 5-HT2A receptor involved in signaling cascades associated to intracellular inflammation and apoptosis in hepatocytes and its role in carbon tetrachloride-induced hepatotoxicity

Previously, we found that the 5-HT2A receptor plays a key role in cell injury. However, the mechanism by which the 5-HT2A receptor mediates intracellular processes remains unclear. In this study, we aimed to clarify this intracellular process in hepatocyte LO2 cells and evaluate its role in CCl4-induced hepatotoxicity in mice. In vitro, both the agonist and overexpression of 5-HT2A receptor could promote 5-HT degradation by upregulating the expression of 5-HT synthases and monoamine oxidase-A (MAO-A) to cause overproduction of ROS in mitochondria. We refer to this as the activation of the 5-HT degradation system (5DS) axis, which leads to the phosphorylation of JNK, p38 MAPK, STAT3, and NF-κB; upregulation of Bax, cleaved-caspase3, and cleaved-caspase9; and downregulation of Bcl-2, followed by apoptosis and oversecretion of TNF-α and IL-1β in cells. This phenomenon could be markedly blocked by the 5-HT2A receptor antagonist, MAO-A inhibitor, or gene-silencing MAO-A. Through protein kinases C epsilon (PKCε) agonist treatment and gene silencing of the PKCε and 5-HT2A receptor, we demonstrated that the 5-HT2A receptor controls 5-HT synthases and MAO-A expression via the PKCε pathway in cells. Unexpectedly, we discovered that PKCε-mediated phosphorylation of the AKT/mTOR pathway is also a consequence of the activation of the 5DS axis. Furthermore, we confirmed that the inhibition of the 5DS axis using the 5-HT2A receptor antagonist could prevent hepatotoxicity induced by CCl4 both in vitro and in vivo, inhibiting the aforementioned signaling cascades, inflammation, and apoptosis, and that the 5DS activation area overlapped the necrotic area of mouse liver. Taken together, we revealed a 5DS axis in hepatocytes that controls the signaling cascades associated with inflammation and apoptosis and confirmed its role in CCl4-induced hepatotoxicity.

Increased adipose catecholamine levels and protection from obesity with loss of Allograft Inflammatory Factor-1

Recent studies implicate macrophages in regulation of thermogenic, sympathetic neuron-mediated norepinephrine (NE) signaling in adipose tissues, but understanding of such non-classical macrophage activities is incomplete. Here we show that male mice lacking the allograft inflammatory factor-1 (AIF1) protein resist high fat diet (HFD)-induced obesity and hyperglycemia. We link this phenotype to higher adipose NE levels that stem from decreased monoamine oxidase A (MAOA) expression and NE clearance by AIF1-deficient macrophages, and find through reciprocal bone marrow transplantation that donor Aif1-/- vs WT genotype confers the obesity phenotype in mice. Interestingly, human sequence variants near the AIF1 locus associate with obesity and diabetes; in adipose samples from participants with obesity, we observe direct correlation of AIF1 and MAOA transcript levels. These findings identify AIF1 as a regulator of MAOA expression in macrophages and catecholamine activity in adipose tissues – limiting energy expenditure and promoting energy storage – and suggest how it might contribute to human obesity.

Monoamine oxidase A attenuates chondrocyte loss and extracellular matrix degradation in osteoarthritis by inducing autophagy

ObjectivesOsteoarthritis (OA) is a prevalent degenerative joint disorder characterized by cartilage destruction and extracellular matrix (ECM) degeneration. Here, we studied the potential function of monoamine oxidase A (MAOA) in OA pathogenesis. MethodsCartilage tissue samples were collected from 33 patients with knee OA and nine normal healthy controls. Sprague-Dawley rats with anterior cruciate ligament transection (ACLT) and primary chondrocytes treated with interleukin (IL)-1β were used as OA animal and cell models, respectively. The effects of adenovirus-mediated MAOA overexpression in OA models were studied using Safranin-O staining, immunohistochemistry, CCK-8 assay, EdU assay, flow cytometry, qRT-PCR, western blotting, and immunofluorescence. ResultsMAOA was identified as an overlapping downregulating gene in the GSE82107, GSE1919, GSE169077, and GSE29746 datasets. MAOA expression was negatively correlated with OA severity. MAOA downregulation was confirmed in ACLT rats and IL-1β-treated chondrocytes. Notably, MAOA overexpression significantly inhibited ACLT-induced OA pathogenesis in rats, as was evidenced by the reduced Osteoarthritis Research Society International (OARSI) score and serum crosslinked C-telopeptides of type II collagen (CTX-II) and cartilage oligomeric matrix protein (COMP) levels. These findings show that MAOA overexpression inhibits extracellular matrix (ECM) degradation and promotes ACLT-induced autophagy. The effects of MAOA on ECM degradation and autophagy were also confirmed in IL-1β-treated primary chondrocytes. Additionally, MAOA protects chondrocytes against IL-1β-induced apoptosis. Furthermore, treating chondrocytes with 3-MA significantly attenuated the protective effects of MAOA. ConclusionMAOA was identified as a downregulated gene in OA. Restoring MAOA expression protects against chondrocyte loss and ECM degradation through autophagy regulation.

Monoamine oxidase A drives neuroendocrine differentiation in prostate cancer

Neuroendocrine transdifferentiation (NED) of prostate cancer (PCa) is the main cause of failure of androgen receptor inhibitor treatment. However, the molecular mechanisms underlying the development of NEPC, especially treatment-induced NEPC, remain unclear. Emerging evidence indicates that elevated monoamine oxidase A (MAOA) contribute to the proliferation, cell stemness, and bone metastasis in PCa. Here, we generated an enzalutamide-induced NED cell model to assess the role of MAOA during NED. Overall, MAOA expression was significantly increased upon Enz long-term exposure and was required for neuroendocrine marker expression. In particular, Enz was found to induce NED via the MAOA/mTOR/HIF-1α signaling axis. Further analyses revealed that the MAOA inhibitor clorgyline(CLG) may bring multiple benefits to CRPC patients, including better therapeutic effect and delays NED. These findings suggest that MAOA may be an important target for the development of anti-NED therapies, thereby providing a novel strategy for the combined application of CLG and AR inhibitors in the clinic.

Aberrant tryptophan metabolism in stromal cells is associated with mesenteric fibrosis in small intestinal neuroendocrine tumors.

BackgroundIncreased levels of serotonin secretion are associated with mesenteric fibrosis (MF) in small intestinal neuroendocrine tumors (SI-NETs). However, the profibrotic potential of serotonin differs between patients, and in this study, we aimed to gain an understanding of the mechanisms underlying this variability. To this end, we analyzed the proteins involved in tryptophan metabolism in SI-NETs.MethodsProteomes of tumor and stroma from primary SI-NETs and paired mesenteric metastases of patients with MF (n = 6) and without MF (n = 6) were identified by liquid chromatography–mass spectrometry (LC-MS). The differential expression of proteins involved in tryptophan metabolism between patients with and without MF was analyzed. Concurrently, monoamine oxidase A (MAO-A) expression was analyzed in the tumor and stromal compartment by immunohistochemistry (IHC) and reported as intensity over area (I/A).ResultsOf the 42 proteins involved in tryptophan metabolism, 20 were detected by LC-MS. Lower abundance of ten proteins was found in mesenteric metastases stroma in patients with MF. No differential expression was found in primary SI-NETs. In patients with MF, IHC showed lower MAO-A expression in the stroma of the primary SI-NETs (median 4.2 I/A vs 6.5 I/A in patients without MF, P = 0.003) and mesenteric metastases (median 2.1 I/A vs 2.8 I/A in patients without MF, P= 0.019).ConclusionWe found a decreased expression of tryptophan and serotonin-metabolizing enzymes in the stroma in patients with MF, most notably in the mesenteric stroma. This might account for the increased profibrotic potential of serotonin and explain the variability in the development of SI-NET-associated fibrotic complications.

Neuroprotective effects of Olea europaea L. fruit extract against cigarette smoke-induced depressive-like behaviors in Sprague-Dawley rats.

Depression is broadly acclaimed as a mental health anomaly and despite advancements in the development of antidepressant drugs, they are linked with side effects. Dietary modifications and medicinal plants like olives can be used as effective strategies due to their antioxidant, immune-modulatory, antiinflammatory, and anticonvulsant properties. Considering the compositional alterations in olive fruits during ripening, the antidepressant potential of olive fruits at different degrees of ripeness, that is, un-ripened (green) and ripened (black) was investigated. Rats were randomly divided into five groups: G0 (Normal diet), G1 (Normal diet+smoke exposure (SE), G2 (Normal diet+SE+Citalopram), G3 (Normal diet+SE+Green olive extract), and G4 (Normal diet+SE+Black olive extract). Depressive-like behaviors were induced in all groups through cigarette smoke exposure except G0 . Green and black olive extracts prevented depressive behaviors by reducing the immobility time of rats in forced swim test and tail suspension test while increased the latency to respond in hot plate assay. Moreover, lipid peroxidation in brain tissue was reduced with citalopram, green, and black olive extracts. Additionally, treatments also enhanced the antioxidant pool of brain tissues. Histological examination revealed that olive extracts and citalopram prevented cigarette smoke-induced moderate to severe necrosis and congestion in the brain parenchyma and elucidated antidepressant potential by improving the expression of monoamine oxidase-A, solute carrier family 6 member 4, and brain-derived neurotrophic factor genes. Conclusively, olives may act as a promising antidepressant agent in ameliorating cigarette smoke-induced depressive-like behaviors. PRACTICAL APPLICATIONS: Olive extracts at both ripening stages revealed an antidepressant-like effect almost similar to the standard antidepressant drug and also prevented oxidative damages. Therefore, from the current findings, it can be recommended that food ingredients with antidepressant potential like olives should be incorporated in future interventions to combat depression/psychiatric anomalies and diet therapy should be encouraged to alleviate lifestyle-related disorders.

Association of Two Variable Number of Tandem Repeats in the Monoamine Oxidase A Gene Promoter with Schizophrenia.

BackgroundMonoamine oxidase-A (MAO-A) decomposes dopamine and serotonin, and decreased MAO-A expression increases monoamine levels and is related to the pathophysiology of schizophrenia. Previous studies have reported that variable number of tandem repeats (VNTR), namely, upstream (u)VNTR, and some single nucleotide polymorphisms (SNPs) in the MAOA gene are associated with schizophrenia.MethodsWe investigated the two VNTRs and their related SNPs (rs6323 and rs1137070) in the MAOA gene promoter in 859 patients with schizophrenia and 826 healthy controls. Distal (d)VNTR and uVNTR were genotyped with fluorescence-based fragment polymerase chain reaction assays, and rs6323 and rs1137070 with TaqMan SNP genotyping assays.ResultsNeither the genotype nor allelic frequency of the VNTRs or SNPs showed significant differences between the schizophrenia and control groups. On the other hand, analysis of the dVNTR-uVNTR-rs6323-rs1137070 haplotype showed significant association for nine repeats (9R)-3R-T-C in female patients (corrected p = 0.0006, odds ratio [confidence interval] = 2.17 [1.446–3.257]).ConclusionOur findings provide novel evidence that MAOA gene polymorphisms are associated with an increased risk of developing schizophrenia in females.

Nephrotoxicity induced by cisplatin is primarily due to the activation of the 5-hydroxytryptamine degradation system in proximal renal tubules

As a widely used anticancer drug in the clinic, cisplatin has obvious side effects, especially nephrotoxicity. Previous studies have suggested that the accumulation of intracellular reactive oxygen species (ROS) is a hallmark of cisplatin-induced acute kidney injury. This study aimed to investigate the relationship between ROS accumulation induced by cisplatin and 5-HT degradation. In vivo, by HE and TUNEL staining, we found that cisplatin-induced renal lesions and apoptotic regions, which were located in proximal tubular epithelial cells, were also the regions in which tryptophan hydroxylase 1 (Tph1), aromatic l-amino acid decarboxylase (AADC), 5-HT2A receptor (5-HT2AR) and monoamine oxidase A (MAO-A) were overexpressed, as determined by immunohistochemistry. Notably, the 5-HT2AR antagonist sarpogrelate hydrochloride (SH) and the AADC inhibitor carbidopa (CDP) significantly attenuated cisplatin-induced increases in serum creatinine and blood urea nitrogen levels, renal ROS levels, oxidative stress (SOD activity and MDA), proinflammatory cytokine levels (NF-κB, TNF-α and IL-1β), proapoptotic factor levels (Bax, Bcl-2, C-caspase 3 and C-caspase 9) and the phosphorylation of p38 and STAT3, as well as renal lesions and apoptosis. The combination of SH and CDP could almost abolish the effects of cisplatin challenge. In vitro, the effects of cisplatin challenge and the inhibitory effects of SH and CDP were also observed in HK-2 cells. Additionally, similar to the combination of SH and CDP, the MAO-A inhibitor clorgyline could also abolish the effects of cisplatin challenge. More importantly, by western blotting, we detected that the upregulation of Tph1, AADC and MAO-A expression induced by cisplatin both in vivo and in vitro could be obviously suppressed by SH to decrease 5-HT synthesis and mitochondrial 5-HT degradation. Altogether, these findings suggested that cisplatin-induced nephrotoxicity is due to the activation of the 5-HT degradation system in proximal tubular epithelial cells, including 5-HT2AR and 5-HT synthesis and degradation. 5-HT2AR plays a role by mediating the expression of MAO-A and the 5-HT synthases Tph1 and AADC.

MAO-A Inhibition by Metaxalone Reverts IL-1β-Induced Inflammatory Phenotype in Microglial Cells.

Experimental and clinical studies have suggested that several neurological disorders are associated with the occurrence of central nervous system neuroinflammation. Metaxalone is an FDA-approved muscle relaxant that has been reported to inhibit monoamine oxidase A (MAO-A). The aim of this study was to investigate whether metaxalone might exert antioxidant and anti-inflammatory effects in HMC3 microglial cells. An inflammatory phenotype was induced in HMC3 microglial cells through stimulation with interleukin-1β (IL-1β). Control cells and IL-1β-stimulated cells were subsequently treated with metaxalone (10, 20, and 40 µM) for six hours. IL-1β stimulated the release of the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), but reduced the anti-inflammatory cytokine interleukin-13 (IL-13). The upstream signal consisted of an increased priming of nuclear factor-kB (NF-kB), blunted peroxisome proliferator-activated receptor gamma (PPARγ), and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) expression. IL-1β also augmented MAO-A expression/activity and malondialdehyde levels and decreased Nrf2 mRNA expression and protein levels. Metaxalone decreased MAO-A activity and expression, reduced NF-kB, TNF-α, and IL-6, enhanced IL-13, and also increased PPARγ, PGC-1α, and Nrf2 expression. The present experimental study suggests that metaxalone has potential for the treatment of several neurological disorders associated with neuroinflammation.

Role of 5-HT degradation in acute liver injury induced by carbon tetrachloride

5-hydroxytryptamine (5-HT) is involved in the pathological processes of several liver diseases. Acute liver injury underlies the development of many liver diseases, but the mechanism remains unclear. We aimed to investigate the role of 5-HT in carbon tetrachloride (CCl4)-induced acute liver injury. Acute liver injury was induced with CCl4 (10 mg/kg) in mice pretreated with the 5-HT2A receptor antagonist sarpogrelate hydrochloride (SH) and the 5-HT synthesis inhibitor carbidopa (CDP). LO2 cells were treated with CCl4, 5-HT or 2,5-dimethoxy-4-idopametamine and pretreated with SH, CDP or the monoamine oxidase A (MAO-A) inhibitor clorgyline. Hematoxylin-eosin staining, immunohistochemistry, Real-time quantitative PCR, western blotting, fluorescent probe and biochemical markers were used to evaluate liver compromise. 5-HT2A receptor, 5-HT synthetase and MAO-A were expressed in hepatocytes; their gene and protein expression were upregulated by CCl4, which led to the degradation of mitochondrial 5-HT and overproduction of reactive oxygen species (ROS). Hepatic injury may be aggravated by ROS, which induce oxidative stress and the phosphorylation of p38 mitogen-activated protein kinase, Jun N-terminal kinase, extracellular regulated protein kinase, signal transducer and activator of transcription 3 and nuclear factor kappa-B. 5-HT2A receptor may contribute to acute liver injury by modulating 5-HT synthase and MAO-A expression. The synergistic action of SH and CDP treatment may inhibit CCl4-induced acute liver injury in a dose-dependent manner. Hence, CCl4-induced acute liver injury is due to an increase in mitochondrial ROS production caused by increased 5-HT degradation and probably involves increases in 5-HT2A receptor expression and 5-HT synthesis.

Bidirectional Cross-talk between MAOA and AR Promotes Hormone-Dependent and Castration-Resistant Prostate Cancer.

Androgen receptor (AR) is the primary oncogenic driver of prostate cancer, including aggressive castration-resistant prostate cancer (CRPC). The molecular mechanisms controlling AR activation in general and AR reactivation in CRPC remain elusive. Here we report that monoamine oxidase A (MAOA), a mitochondrial enzyme that degrades monoamine neurotransmitters and dietary amines, reciprocally interacts with AR in prostate cancer. MAOA was induced by androgens through direct AR binding to a novel intronic androgen response element of the MAOA gene, which in turn promoted AR transcriptional activity via upregulation of Shh/Gli-YAP1 signaling to enhance nuclear YAP1-AR interactions. Silencing MAOA suppressed AR-mediated prostate cancer development and growth, including CRPC, in mice. MAOA expression was elevated and positively associated with AR and YAP1 in human CRPC. Finally, genetic or pharmacologic targeting of MAOA enhanced the growth-inhibition efficacy of enzalutamide, darolutamide, and apalutamide in both androgen-dependent and CRPC cells. Collectively, these findings identify and characterize an MAOA-AR reciprocal regulatory circuit with coamplified effects in prostate cancer. Moreover, they suggest that cotargeting this complex may be a viable therapeutic strategy to treat prostate cancer and CRPC. SIGNIFICANCE: MAOA and AR comprise a positive feedback loop in androgen-dependent and CRPC, providing a mechanistic rationale for combining MAOA inhibition with AR-targeted therapies for prostate cancer treatment.

Elevated serotonin alters whole-blood expression of serotonin receptor and metabolism genes in the lactating dairy cow

Serotonin's role as a hormone has been demonstrated through modulating calcium metabolism, energy homeostasis, and immune function in the preweaned and lactating bovine. Recently, manipulation of the serotonergic axis in calves via administration of 5-hydroxy-l-tryptophan (5-HTP), the serotonin precursor, elicited immunomodulatory effects and regulated serotonin transport and metabolism genes in leukocytes. However, serotonin's ability to modulate whole-blood gene expression in lactating dairy cows is unknown. Our objective was to explore the effect of infusing 5-HTP on whole-blood expression of genes regulating serotonin transport (reuptake transporter), signaling (receptors), metabolism (synthesis and degradation), and cytokines in dairy cows. Twelve lactating multiparous Holstein dairy cows were blocked by parity, milk production, and days in milk in a randomized complete block design and randomly assigned to intravenous infusion of either 1 L of 1.5 mg/kg 5-HTP dissolved in saline (n = 6) or 1 L of saline solution (n = 6) for 3 consecutive days. Whole blood was collected at 48, 56, and 72 h relative to termination of first infusion to analyze whole-blood gene expression. Infusion of 5-HTP increased whole-blood mRNA expression of monoamine oxidase-A and serotonin receptor 7 across the experimental period. Forty-eight hours from termination of first infusion, the mRNA of monoamine oxidase-A, serotonin reuptake transporter, and serotonin receptor 7 were increased in blood relative to the control. Interleukin-8 concentrations and mRNA were unchanged in response to 5-HTP infusion. Collectively, these data suggest that infusion of 5-HTP may alter mRNA of serotonin metabolism, transport, and signaling genes in whole blood of lactating dairy cows.

Elevated MAOA impairs intracellular β 1 ‐adrenegic signaling and myocardial contractility in heart failure

Rationale: We recently identified a pool of β1ARs at the sarcoplasmic reticulum (SR) senses cytosolic catecholamines and promotes cardiac contractility. Monoamine oxidase A (MAOA), the major enzyme metabolizing myocardial catecholamines is upregulated in heart failure (HF) together with blunted β1AR signaling. However, the regulation of intracellular β1ARs signaling in HF remains unknown. Objective To uncover the role of MAOA in the spatiotemporal regulation of intracellular β1AR signaling and cardiac contractility. Methods and Results Echocardiogram analysis showed that cardiac-specific deletion (cKO) or pharmacological inhibition of MAOA did not affect the baseline cardiac output but significantly amplified the inotropy of catecholamine (epinephrine) in vivo. Enzyme immunoassay revealed elevated catecholamine concentrations and cAMP/PKA activities in MAOA-cKO mice hearts compared with their flox/flox (FF) littermates. We measured the subcellular-localized β1AR in living cardiomyocytes using PKA biosensors targeted at SR or plasma membrane (PM). Compared with FF cardiomyocytes, MAOA-cKO exhibited an increased PKA activity at SR, but not PM upon epinephrine stimulation. Consistently, phosphorylation of phospholamban (PLB), a major target of SR-localized β1AR signals, was enhanced by MAOA-cKO. More importantly, deleting MAOA increased the response of calcium transients and contractility to epinephrine. Blocking the entry of catecholamines by organic cation transporter 3 (OCT3) inhibitor abolished the differential effects in MAOA-cKO vs FF. Similarly, the effect of MAOA-cKO on intracellular β1AR/PKA/PLB signaling and cardiac excitation-contraction coupling (EC-coupling) was recapitulated by pharmacological inhibition of MAOA. In contrast, overexpression of MAOA in cardiomyocytes suppressed epinephrine-induced PKA activation at the SR, PLB phosphorylation and contractility. Furthermore, the increased expression of MAOA in failing cardiomyocytes suppressed activation of intracellular β1AR and attenuated PKA phosphorylation of PLB and inotropic responses. Inhibition of MAOA restored intracellular β1AR signaling and EC coupling in failing cardiomyocytes, and rescued the inotropy response in HF mice. Conclusion MAOA modulates catecholamine-promoted EC coupling via tuning the intracellular β1AR signaling and PKA phosphorylation of PLB. Inhibition of MAOA restores β1AR/PKA signaling at the SR and cardiac contractility in HF.

α-Synuclein Up-regulates Monoamine Oxidase A Expression and Activity via Trans-Acting Transcription Factor 1.

Abnormal α-Synuclein (α-SYN) aggregates are the pathological hallmarks of Parkinson’s disease (PD), which may affect dopamine (DA) neuron function and DA metabolism. Monoamine oxidase A (MAOA) is an enzyme located on the outer mitochondrial membrane that catalyzes the oxidative deamination of DA. Both α-SYN and MAOA are associated with PD pathogenesis, suggesting possible crosstalk between these two molecules. In the present study, we aimed to investigate the potential impacts of α-SYN on MAOA function and further explore the underlying mechanisms. Our study showed that overexpression of α-SYN [both wild-type (WT) and A53T] increased MAOA function via upregulating its expression without impacting MAOA stability. Overexpression of α-SYNWT or α-SYNA53T enhanced the transcription activity of the MAOA promoter region containing the binding sites of cell division cycle associated 7 like (R1, a transcriptional repressor of MAOA) and trans-acting transcription factor 1 (Sp1, a transcription factor of MAOA). Interestingly, α-SYN selectively increased Sp1 expression, thereby enhancing the binding capacity of Sp1 with MAOA promoter to increase MAOA expression. Taken together, our findings demonstrate that α-SYN can upregulate MAOA expression via modulation of Sp1 and may shed light on future studies of α-SYN associated PD pathogenesis.