Exploring Sonic Hedgehog Cell Signaling in Neurogenesis: Its Potential Role in Depressive Behavior

Olfactory bulb neurogenesis depending on signaling in the subventricular zone

Olfaction is a crucial sense that is essential for the well-being and survival of individuals. Olfactory bulb (OB) is the first olfactory relay station, and its function depends on newly generated neurons from the subventricular zone (SVZ). These newly born neurons constantly migrate through the rostral migratory stream to integrate into existing neural networks within the OB, thereby contributing to olfactory information processing. However, the mechanisms underlying the contribution of SVZ adult neurogenesis to OB neurogenesis remain largely elusive. Adult neurogenesis is a finely regulated multistep process involving the proliferation of adult neural stem cells (aNSCs) and neural precursor cells, as well as the migration and differentiation of neuroblasts, and integration of newly generated neurons into preexisting neuronal circuitries. Recently, extensive studies have explored the mechanism of SVZ and OB neurogenesis. This review focused on elucidating various molecules and signaling pathways associated with OB neurogenesis dependent on the SVZ function. A better understanding of the mechanisms underlying the OB neurogenesis on the adult brain is an attractive prospect to induce aNSCs in SVZ to generate new neurons to ameliorate olfactory dysfunction that is involved in various diseases. It will also contribute to developing new strategies for the human aNSCs-based therapies.

Regulatory mechanisms of stem cell differentiation: Biotechnological applications for neurogenesis

The world population's life expectancy is growing, and neurodegenerative disorders common in old age require more efficient therapies. In this context, neural stem cells (NSCs) are imperative for the development and maintenance of the functioning of the nervous system and have broad therapeutic applicability for neurodegenerative diseases. Therefore, knowing all the mechanisms that govern the self-renewal, differentiation, and cell signaling of NSC is necessary. This review will address some of these aspects, including the role of growth and transcription factors, epigenetic modulators, microRNAs, and extracellular matrix components. Furthermore, differentiation and transdifferentiation processes will be addressed as therapeutic strategies showing their significance for stem cell-based therapy.

Therapeutic implication of Sonic Hedgehog as a potential modulator in ischemic injury

Sonic Hedgehog (SHh) is a homology protein that is involved in the modeling and development of embryonic tissues. As SHh plays both protective and harmful roles in ischemia, any disruption in the transduction and regulation of the SHh signaling pathway causes ischemia to worsen. The SHh signal activation occurs when SHh binds to the receptor complex of Ptc-mediated Smoothened (Smo) (Ptc-smo), which initiates the downstream signaling cascade. This article will shed light on how pharmacological modifications to the SHh signaling pathway transduction mechanism alter ischemic conditions via canonical and non-canonical pathways by activating certain downstream signaling cascades with respect to protein kinase pathways, angiogenic cytokines, inflammatory mediators, oxidative parameters, and apoptotic pathways. The canonical pathway includes direct activation of interleukins (ILs), angiogenic cytokines like hepatocyte growth factor (HGF), platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), and hypoxia-inducible factor alpha (HIF-), which modulate ischemia. The non-canonical pathway includes indirect activation of certain pathways like mTOR, PI3K/Akt, MAPK, RhoA/ROCK, Wnt/-catenin, NOTCH, Forkhead box protein (FOXF), Toll-like receptors (TLR), oxidative parameters such as GSH, SOD, and CAT, and some apoptotic parameters such as Bcl2. This review provides comprehensive insights that contribute to our knowledge of how SHh impacts the progression and outcomes of ischemic injuries.

The role of Smo-Shh/Gli signaling activation in the prevention of neurological and ageing disorders

Sonic hedgehog (Shh) signaling is an essential central nervous system (CNS) pathway involved during embryonic development and later life stages. Further, it regulates cell division, cellular differentiation, and neuronal integrity. During CNS development, Smo-Shh signaling is significant in the proliferation of neuronal cells such as oligodendrocytes and glial cells. The initiation of the downstream signalling cascade through the 7-transmembrane protein Smoothened (Smo) promotes neuroprotection and restoration during neurological disorders. The dysregulation of Smo-Shh is linked to the proteolytic cleavage of GLI (glioma-associated homolog) into GLI3 (repressor), which suppresses target gene expression, leading to the disruption of cell growth processes. Smo-Shh aberrant signalling is responsible for several neurological complications contributing to physiological alterations like increased oxidative stress, neuronal excitotoxicity, neuroinflammation, and apoptosis. Moreover, activating Shh receptors in the brain promotes axonal elongation and increases neurotransmitters released from presynaptic terminals, thereby exerting neurogenesis, anti-oxidation, anti-inflammatory, and autophagy responses. Smo-Shh activators have been shown in preclinical and clinical studies to help prevent various neurodegenerative and neuropsychiatric disorders. Redox signalling has been found to play a critical role in regulating the activity of the Smo-Shh pathway and influencing downstream signalling events. In the current study ROS, a signalling molecule, was also essential in modulating the SMO-SHH gli signaling pathway in neurodegeneration. As a result of this investigation, dysregulation of the pathway contributes to the pathogenesis of various neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD).Thus, Smo-Shh signalling activators could be a potential therapeutic intervention to treat neurocomplications of brain disorders.

Protective Role and Functional Engineering of Neuropeptides in Depression and Anxiety: An Overview

Behavioral disorders, such as anxiety and depression, are prevalent globally and touch children and adults on a regular basis. Therefore, it is critical to comprehend how these disorders are affected. It has been demonstrated that neuropeptides can influence behavior, emotional reactions, and behavioral disorders. This review highlights the majority of the findings demonstrating neuropeptides' behavioral role and functional engineering in depression and anxiety. Gut-brain peptides, hypothalamic releasing hormone peptides, opioid peptides, and pituitary hormone peptides are the four major groups of neuropeptides discussed. Some neuropeptides appear to promote depression and anxiety-like symptoms, whereas others seem to reduce it, all depending on the receptors they are acting on and on the brain region they are localized in. The data supplied here are an excellent starting point for future therapy interventions aimed at treating anxiety and depression.

Gut brain interaction theory reveals gut microbiota mediated neurogenesis and traditional Chinese medicine research strategies

Adult neurogenesis is the process of differentiation of neural stem cells (NSCs) into neurons and glial cells in certain areas of the adult brain. Defects in neurogenesis can lead to neurodegenerative diseases, mental disorders, and other maladies. This process is directionally regulated by transcription factors, the Wnt and Notch pathway, the extracellular matrix, and various growth factors. External factors like stress, physical exercise, diet, medications, etc., affect neurogenesis and the gut microbiota. The gut microbiota may affect NSCs through vagal, immune and chemical pathways, and other pathways. Traditional Chinese medicine (TCM) has been proven to affect NSCs proliferation and differentiation and can regulate the abundance and metabolites produced by intestinal microorganisms. However, the underlying mechanisms by which these factors regulate neurogenesis through the gut microbiota are not fully understood. In this review, we describe the recent evidence on the role of the gut microbiota in neurogenesis. Moreover, we hypothesize on the characteristics of the microbiota-gut-brain axis based on bacterial phyla, including microbiota's metabolites, and neuronal and immune pathways while providing an outlook on TCM's potential effects on adult neurogenesis by regulating gut microbiota.

Compound Tongluo Decoction inhibits endoplasmic reticulum stress-induced ferroptosis and promoted angiogenesis by activating the Sonic Hedgehog pathway in cerebral infarction

ETHNOPHARMACOLOGICAL RELEVANCE

Cerebral infarction is one of the most common types of cerebrovascular diseases that threaten people's health. Compound Tongluo Decoction (CTLD), a traditional Chinese medicine formula, has various pharmacological activities, including the alleviation of cerebral infarction symptoms.

AIM OF THE STUDY

This study aims to explore the potential mechanism by which CTLD alleviates cerebral infarction.

MATERIAL AND METHODS

Middle cerebral artery occlusion (MCAO) rat model and oxygen-glucose deprivation and reperfusion (OGD/R) cell model were established for research. The expression of proteins related to endoplasmic reticulum (ER) stress, ferroptosis, Sonic Hedgehog (SHH) pathway and angiogenesis was analyzed by Western blot analysis. The expression of CD31 was detected by immunofluorescence to investigate angiogenesis. In addition, the expression of GRP78 and XBP-1 in brain tissues was investigated by immunohistochemistry. With the application of Prussian blue staining, iron deposition in brain tissue was detected. The levels of reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD) were detected using ELISA kits. The angiogenesis was analyzed by tube formation assay.

RESULTS

The results presented in this research showed that CTLD and 4-phenyl butyric acid (4-PBA; the inhibitor of ER stress) could alleviate cerebral infarction. Mechanistically, CTLD and 4-PBA rescued ER stress and ferroptosis, but promoted SHH signaling in rats with cerebral infarction. In addition, cerebral infarction exhibited a high level of angiogenesis, which was aggravated by CTLD but suppressed by 4-PBA. Furthermore, CTLD inhibited ER stress and ferroptosis, but promoted SHH signaling and angiogenesis in OGD/R-induced PC12 cells, which was partly abolished by SANT-1, an antagonist of SHH signaling.

CONCLUSION

In conclusion, this study revealed that CTLD might inhibit ferroptosis induced by endoplasmic reticulum stress and promote angiogenesis by activating the Sonic Hedgehog pathway in rats with cerebral infarction.

5-HT Receptors and the Development of New Antidepressants

Serotonin modulates several physiological and cognitive pathways throughout the human body that affect emotions, memory, sleep, and thermal regulation. The complex nature of the serotonergic system and interactions with other neurochemical systems indicate that the development of depression may be mediated by various pathomechanisms, the common denominator of which is undoubtedly the disturbed transmission in central 5-HT synapses. Therefore, the deliberate pharmacological modulation of serotonergic transmission in the brain seems to be one of the most appropriate strategies for the search for new antidepressants. As discussed in this review, the serotonergic system offers great potential for the development of new antidepressant therapies based on the combination of SERT inhibition with different pharmacological activity towards the 5-HT system. The aim of this article is to summarize the search for new antidepressants in recent years, focusing primarily on the possibility of benefiting from interactions with various 5-HT receptors in the pharmacotherapy of depression.