Prapimpun Wongchitrat

Melatonin regulates aging and neurodegeneration through energy metabolism, epigenetics, autophagy and circadian rhythm pathways.

Brain aging is linked to certain types of neurodegenerative diseases and identifying new therapeutic targets has become critical. Melatonin, a pineal hormone, associates with molecules and signaling pathways that sense and influence energy metabolism, autophagy, and circadian rhythms, including insulin-like growth factor 1 (IGF-1), Forkhead box O (FoxOs), sirtuins and mammalian target of rapamycin (mTOR) signaling pathways. This review summarizes the current understanding of how melatonin, together with molecular, cellular and systemic energy metabolisms, regulates epigenetic processes in the neurons. This information will lead to a greater understanding of molecular epigenetic aging of the brain and anti-aging mechanisms to increase lifespan under healthy conditions.

Effect of amphetamine on the clock gene expression in rat striatum

Drug addicts have severe disruptions in many physiological and behavioral rhythms, such as the sleep/wake cycle. Interestingly, amphetamine, a psychostimulant, is able to alter many circadian patterns, which are independent of the master biological clock located in the suprachiasmatic nucleus. To increase our understanding of the circadian regulation of amphetamine on clock gene expression, rats received subcutaneous injections of d-amphetamine and the clock gene mRNA levels were analyzed using real-time PCR to obtain a daily profile. In the striatum, acute injection of d-amphetamine did not alter Period (Per)1, Per2 and Reverse erythroblastosis virus α (Rev-erbα) expressions. Chronic administration shifted the phase of Per1 and Per2 expressions from a nocturnal to diurnal pattern and advance shifted the peak of Rev-erbα in d-amphetamine-treated animals. In contrast, the rhythm of Brain and muscle Arnt-like protein-1 (Bmal1) was shifted from a diurnal to a nocturnal pattern by both acute and chronic treatments. These results demonstrated that chronic d-amphetamine treatment altered the expression of clock genes in the striatum. This might further influence the expression of related gene within the striatum and lead to behavioral and physiological changes which are associated to drug addiction.

A Noradrenergic Sensitive Endogenous Clock Is Present in the Rat Pineal Gland

The aim of this study was to examine the occurrence of endogenous oscillations of Per1, Per2, Bmal1 and Rev-erbα genes in rat pineal explants and to investigate their regulation by adrenergic ligands. Our results show a significant and sustained rhythm of Per2,Bmal1 and Rev-erbα gene expression for up to 48 h in cultured pineal gland with a pattern similar to that observed in vivo. By contrast, the rhythms of Per1 and Aa-nat, the rate-limiting enzyme for melatonin synthesis, were strongly attenuated after 24 h in culture. Addition of the exogenous adrenergic agonist isoproterenol on cultured pineal glands induced a short-term increase in mRNA levels of Per1 and Aa-nat, but not those of Per2,Bmal1 and Rev-erbα. This study demonstrates that the rat pineal gland hosts a circadian oscillator as evidenced by the sustained, noradrenergic-independent, endogenous oscillations of Per2, Bmal1 and Rev-erbα mRNA levels in cultured tissues. Only expression of Per1 was stimulated by adrenergic ligands suggesting that, in vivo, the adrenergic input could synchronize the pineal clock by acting selectively on Per1.

Melatonin attenuates the high-fat diet and streptozotocin-induced reduction in rat hippocampal neurogenesis.

A deviant level of melatonin in blood circulation has been associated with the development of diabetes and with learning and memory deficiencies. Melatonin might have an important function in diabetes control; however, the mechanism of melatonin in diabetes remains unknown. The present study aimed to investigate the hyperglycemic condition induced by high-fat diet (HFD) feeding and streptozotocin (STZ) injection and to examine the effect of melatonin on adult hippocampal functions. HFD-fed and STZ-treated rats significantly increased blood glucose level. The present study showed that HFD-fed and STZ-treated rats significantly impaired memory in the Morris Water Maze task, reduced neurogenesis in the hippocampus shown by a reduction in nestin, doublecortin (DCX) and β-III tubulin immunoreactivities, reduced axon terminal markers, synaptophysin, reduced dendritic marker including postsynaptic density 95 (PSD-95) and the glutamate receptor subunit NR2A. Moreover, a significant downregulation of melatonin receptor, insulin receptor-β (IR-β) and both p-IR-β and phosphorylated extracellular signal-regulated kinase (p-ERK) occurred in HFD-fed and STZ-treated rats, while the level of glial fibrillary acidic protein (GFAP) increased. Treatment of melatonin, rats had shorter escape latencies and remained in the target quadrant longer compared to the HFD-fed and STZ-treated rats. Melatonin attenuated the reduction of neurogenesis, synaptogenesis and the induction of astrogliosis. Moreover, melatonin countered the reduction of melatonin receptor, insulin receptor and downstream signaling pathway for insulin. Our data suggested that the dysfunction of insulin signaling pathway occurred in the diabetes may provide a convergent mechanism of hippocampal impaired neurogenesis and synaptogenesis lead to impair memory while melatonin reverses these effects, suggesting that melatonin may reduce the pathogenesis of diabetes.

Exploring the epigenetic drug discovery landscape

ABSTRACT Introduction: Epigenetic modification has been implicated in a wide range of diseases and the ability to modulate such systems is a lucrative therapeutic strategy in drug discovery. Areas covered: This article focuses on the concepts and drug discovery aspects of epigenomics. This is achieved by providing a survey of the following concepts: (i) factors influencing epigenetics, (ii) diseases arising from epigenetics, (iii) epigenetic enzymes as druggable targets along with coverage of existing FDA-approved drugs and pharmacological agents, and (iv) drug repurposing/repositioning as a means for rapid discovery of pharmacological agents targeting epigenetics. Expert opinion: Despite significant interests in targeting epigenetic modifiers as a therapeutic route, certain classes of target proteins are heavily studied while some are less characterized. Thus, such orphan target proteins are not yet druggable with limited report of active modulators. Current research points towards a great future with novel drugs directed to the many complex multifactorial diseases of humans, which are still often poorly understood and difficult to treat.

High-fat diet–induced plasma protein and liver changes in obese rats can be attenuated by melatonin supplementation

Obesity triggers changes in protein expression in various organs that might participate in the pathogenesis of obesity. Melatonin has been reported to prevent or attenuate such pathological protein changes in several chronic diseases. However, such melatonin effects on plasma proteins have not yet been studied in an obesity model. Using a proteomic approach, we investigated the effect of melatonin on plasma protein profiles after rats were fed a high-fat diet (HFD) to induce obesity. We hypothesized that melatonin would attenuate abnormal protein expression in obese rats. After 10weeks of the HFD, animals displayed increased body weight and fat accumulation as well as increased glucose levels, indicating an obesity-induced prediabetes mellitus-like state. Two-dimensional gel electrophoresis and liquid chromatography-mass spectrometry/mass spectrometry revealed 12 proteins whose expression was altered in response to the HFD and the melatonin treatment. The altered proteins are related to the development of liver pathology, such as cirrhosis (α1-antiproteinase), thrombosis (fibrinogen, plasminogen), and inflammation (mannose-binding protein A, complement C4, complement factor B), contributing to liver steatosis or hepatic cell death. Melatonin treatment most probably reduced the severity of the HFD-induced obesity by reducing the amplitude of HFD-induced plasma protein changes. In conclusion, we identified several potential biomarkers associated with the progression of obesity and its complications, such as liver damage. Furthermore, our findings reveal melatonins beneficial effect of attenuating plasma protein changes and liver pathogenesis in obese rats.

Development of an immunoFET biosensor for the detection of biotinylated PCR product

ImmunoFET (IMFET) biosensor is a simple platform for the detection of biotinylated products of polymerase chain reaction (PCR). Construction of the IMFET biosensor started with adsorption of 1.5 mg/mL of protein A (PA) onto the insulated gate surface of ISFET for 90 min. Next, the immobilized 1/500 dilution of anti-biotin antibody was adsorbed onto the PA layer for 60 min. The IMFET biosensor was subsequently ready for detection of the biotinylated amplicon. The IMFET biosensor showed highly specific binding to the biotinylated PCR product of the phaE gene of Haloquadratum walsbyi DSM 16854. The phaE gene is a biomarker of polyhydroxyalkanoate (PHA) producers that contain PHA synthase class III. The lowest amount of DNA template of H. walsbyi DSM 16854 that the IMFET biosensor could detect was 125 fg. The IMFET biosensor has a lower amount of detection compared with a DNA lateral flow biosensor from our previous study. The degree of linearity of the biosensor signal was influenced by the concentration of the biotinylated amplicon. The IMFET biosensor also has a short response time (approximately 30 times) to detect the phaE amplicon compared to an agarose gel electrophoresis. The IMFET biosensor is a promising tool for the detection of the biotinylated PCR product, and it can be integrated into a micro total analysis system (μTAS).

Attenuation of oxidative stress-induced neuronal cell death by Hydnophytum formicar-um Jack.

Objective: To investigate protective effects of Hydnophytum formicarum Jack. (H. formicarum) extracts via regulation of SIRT1-FOXO3a-ADAM10 signaling and antioxidant activity against H2O2-induced neurotoxicity in neuroblastoma SH-SY5Y cells. Methods: Cell viability and apoptosis of neuronal cells pretreated with H. formicarum Jack. extracts under oxidative stress were determined by MTT assay and flow cytometry. The intracellular reactive oxygen species (ROS) was performed using Carboxy-DCFDA assay. Additionally, a profile of protein expressions related to neuroprotection was detected by western blot analysis. Results: The plant extracts (methanol and ethyl acetate) elicited protective effects on the neuronal cell death as performed by the MTT assay and by apoptosis analysis via the activation of BCL-2. Both ethyl acetate and methanol extracts exerted inhibitory effects against H2O2-induced ROS generation in the SH-SY5Y cells. Furthermore, the possible mechanism of neuroprotection of H. formicarum Jack. was observed through its antioxidant properties by maintaining the levels of catalase and SOD2 proteins as well as activating SIRT1-FOXO3a pathway. Importantly, pretreatment of neuronal cells with H. formicarum Jack. significantly recovered the levels of ADAM10 protein compared with the H2O2 treatment alone. Conclusions: The recent findings suggest the protective effects of H. formicarum Jack. plant extracts on attenuating H2O2-induced neurotoxicity in human SH-SY5Y cells.