New insight in expression, transport, and secretion of brain-derived neurotrophic factor: Implications in brainrelated diseases

Brain-derived neurotrophic factor(BDNF) attracts increasing attention from both research and clinical fields because of its important functions in the central nervous system. An adequate amount of BDNF is critical to develop and maintain normal neuronal circuits in the brain. Given that loss of BDNF function has beenreported in the brains of patients with neurodegenerative or psychiatric diseases, understanding basic properties of BDNF and associated intracellular processes is imperative. In this review, we revisit the gene structure, transcription, translation, transport and secretion mechanisms of BDNF. We also introduce implications of BDNF in several brain-related diseases including Alzheimer's disease, Huntington's disease, depression and schizophrenia.

Functional interactions between steroid hormones and neurotrophin BDNF

Brain-derived neurotrophic factor(BDNF),a critical neurotrophin,regulates many neuronal aspects including cell differentiation,cell survival,neurotransmission,and synaptic plasticity in the central nervous system(CNS) .Though BDNF has two types of receptors,high affinity tropomyosin-related kinase(Trk) B and low affinity p75 receptors,BDNF positively exerts its biological effects on neurons via activation of TrkB and of resultant intracellular signaling cascades including mitogenactivated protein kinase/extracellular signal-regulated protein kinase,phospholipase Cγ,and phosphoinositide 3-kinase pathways.Notably,it is possible that alteration in the expression and/or function of BDNF in the CNS is involved in the pathophysiology of various brain diseases such as stroke,Parkinson's disease,Alzheimer's disease,and mental disorders.On the other hand,glucocorticoids,stress-induced steroid hormones,also putatively contribute to the pathophysiology of depression.Interestingly,in addition to the reduction in BDNF levels due to increased glucocorticoid exposure,current reports demonstrate possible interactions between glucocorticoids and BDNF-mediated neuronal functions. Other steroid hormones,such as estrogen,are involved in not only sexual differentiation in the brain,but also numerous neuronal events including cell survival and synaptic plasticity.Furthermore,it is well known that estrogen plays a role in the pathophysiology of Parkinson's disease,Alzheimer's disease,and mental illness,while serving to regulate BDNF expression and/or function.Here,we present a broad overview of the current knowledge concerning the association between BDNF expression/function and steroid hormones(glucocorticoids and estrogen).

COVID-19:A pandemic that threatens physical and mental health by promoting physical inactivity

Ever since the outbreak of Coronavirus disease 2019(COVID-19)in late 2019,it has killed millions of people worldwide.Even people not stricken by this disease are not spared from its negative economic,social,and healthrelated drawbacks.This commentary provides insight into the potential mechanisms involved in the development of depression and emotional negativity escalating during the current pandemic.In particular,preventive measures of COVID-19,such as staying at home,are sedentarism measures that decrease physical activity.Physical inactivity alters gut microbiome structure in a fashion that promotes gut dysbiosis and flaring of systemic inflammation,leading to the buildup of body fat.Obesity,which contributes to a trail of health-depleting disorders,furthers gut microbial disintegration while fat tissue stimulates the release of cytokines,promotes metabolic resistance,and alters signaling involved in the production of antioxidants.As a result,the body gets flooded by toxic molecules such pro-inflammatory mediators,free radicals,and advanced glycation end products.These toxic molecules alter cellular function in all body tissues,including those of the brain.Neuroinflammation is associated with progressive declines in cognitive and motor functions along with dysregulation in emotions.Counteracting the sedentarism enforced by the COVID-19 pandemic through the participation in suitable indoors activities and the intake of healthy food is likely to protect against or revert physiological impairments that may affect people retreating to their homes during the current crisis,eventually restoring physical and mental health.