Lentivirus-mediated delivery of sonic hedgehog into the striatum stimulates neuroregeneration in a rat model of Parkinson disease

Total saponins from Trillium tschonoskii Maxim promote neurological recovery in model rats with post-stroke cognitive impairment

Total saponins from Trillium tschonoskii Maxim (TSTT), a bioactive component of local natural herbs in the Enshi area, China, have been demonstrated to have functions of restoring cognitive capacity and promoting axonal regeneration post-stroke, but the mechanism of this process remains unclear. The hippocampus is a critical tissue for controlling learning and memory capacity, and the sonic hedgehog (Shh) signaling pathway plays a major role in the patterning and synaptic plasticity of hippocampal neural circuits. Therefore, we aimed to investigate whether TSTT could restore learning and cognitive functions by modulating the Shh pathway in rats with post-stroke cognitive impairment (PSCI). The ischemia model was established by permanent middle cerebral artery occlusion (MCAO) in 100 Sprague-Dawley (SD) rats, and the model rats were administered using TSTT (100 mg/kg) or donepezil hydrochloride as the positive control (daily 0.45 mg/kg, DON) for 4 weeks after the operation. As assessed by the Morris water maze test, the cognitive function of PSCI rats was significantly improved upon TSTT treatment. Meanwhile, the cerebral infarct volume reduced with TSTT, as shown by HE and TTC staining, and the number of Nissl bodies and dendritic spine density were significantly increased, as shown by Nissl and Golgi staining. In addition, TSTT upregulated PSD-95, SYN, and GAP-43, and inhibited neuronal apoptosis, as evidenced by increased Bcl-2 levels along with decreased Bax and caspase-3 expression. TSTT could also significantly upregulate Shh, Ptch1, Smo, and Gli1 proteins, indicating the activation of the Shh signaling pathway. Therefore, TSTT can protect PSCI rats by inhibiting apoptosis and promoting neuronal synaptic remodeling. The Shh pathway is also involved.

Developmental pathways linked to the vulnerability of adult midbrain dopaminergic neurons to neurodegeneration

The degeneration of dopaminergic and other neurons in the aging brain is considered a process starting well beyond the infantile and juvenile period. In contrast to other dopamine-associated neuropsychiatric disorders, such as schizophrenia and drug addiction, typically diagnosed during adolescence or young adulthood and, thus, thought to be rooted in the developing brain, Parkinson's Disease (PD) is rarely viewed as such. However, evidences have accumulated suggesting that several factors might contribute to an increased vulnerability to death of the dopaminergic neurons at an already very early (developmental) phase in life. Despite the remarkable ability of the brain to compensate such dopamine deficits, the early loss or dysfunction of these neurons might predispose an individual to suffer from PD because the critical threshold of dopamine function will be reached much earlier in life, even if the time-course and strength of naturally occurring and age-dependent dopaminergic cell death is not markedly altered in this individual. Several signaling and transcriptional pathways required for the proper embryonic development of the midbrain dopaminergic neurons, which are the most affected in PD, either continue to be active in the adult mammalian midbrain or are reactivated at the transition to adulthood and under neurotoxic conditions. The persistent activity of these pathways often has neuroprotective functions in adult midbrain dopaminergic neurons, whereas the reactivation of silenced pathways under pathological conditions can promote the survival and even regeneration of these neurons in the lesioned or aging brain. This article summarizes our current knowledge about signaling and transcription factors involved in midbrain dopaminergic neuron development, whose reduced gene dosage or signaling activity are implicated in a lower survival rate of these neurons in the postnatal or aging brain. It also discusses the evidences supporting the neuroprotection of the midbrain dopaminergic system after the external supply or ectopic expression of some of these secreted and nuclear factors in the adult and aging brain. Altogether, the timely monitoring and/or correction of these signaling and transcriptional pathways might be a promising approach to a much earlier diagnosis and/or prevention of PD.

Long-Term Effects of Ionizing Radiation on the Hippocampus: Linking Effects of the Sonic Hedgehog Pathway Activation with Radiation Response

Radiation therapy represents one of the primary treatment modalities for primary and metastatic brain tumors. Although recent advances in radiation techniques, that allow the delivery of higher radiation doses to the target volume, reduce the toxicity to normal tissues, long-term neurocognitive decline is still a detrimental factor significantly affecting quality of life, particularly in pediatric patients. This imposes the need for the development of prevention strategies. Based on recent evidence, showing that manipulation of the Shh pathway carries therapeutic potential for brain repair and functional recovery after injury, here we evaluate how radiation-induced hippocampal alterations are modulated by the constitutive activation of the Shh signaling pathway in Patched 1 heterozygous mice (Ptch1^+/-). Our results show, for the first time, an overall protective effect of constitutive Shh pathway activation on hippocampal radiation injury. This activation, through modulation of the proneural gene network, leads to a long-term reduction of hippocampal deficits in the stem cell and new neuron compartments and to the mitigation of radio-induced astrogliosis, despite some behavioral alterations still being detected in Ptch1^+/- mice. A better understanding of the pathogenic mechanisms responsible for the neural decline following irradiation is essential for identifying prevention measures to contain the harmful consequences of irradiation. Our data have important translational implications as they suggest a role for Shh pathway manipulation to provide the therapeutic possibility of improving brain repair and functional recovery after radio-induced injury.

[G-protein coupled receptor Smo positively regulates proliferation and migration of adult neural stem cells in vitro]

OBJECTIVE

To investigate the role of G-protein coupled receptor Smoothened (Smo) in regulating proliferation and migration of adult neural stem cells (ANSCs) and explore the underlying mechanism.

METHODS

Cultured ANSCs were treated with purmorphamine (PM, an agonist of Smo) or cyclopamine (CPM, an inhibitor of Smo), and the changes in cell proliferation migration abilities were assessed using cell counting kit-8 (CCK8) assay and wound healing assay, respectively. The mRNA expressions of membrane receptor Patched 1 (Ptch1), Smo, glioma-associated oncogene homolog 1 (Gli1), axon guidance cue slit1 (Slit1) and brain-derived neurotrophic factor (BDNF) in the treated cells were detected using real-time quantitative PCR (RT-PCR).

RESULTS

PM significantly promoted the proliferation (P < 0.01) and migration of ANSCs (P < 0.01), and up-regulated the mRNA expressions of Ptch1, Smo, Gli1, Slit1 and BDNF. Treatment with CPM significantly inhibited the proliferation and migration of ANSCs.

CONCLUSION

Modulating Smo activity can positively regulate the proliferation and migration of ANSCs possibly by regulating the expressions of BDNF and Slit1.

Hedgehog Signaling Modulates Glial Proteostasis and Lifespan

The conserved Hedgehog signaling pathway has well-established roles in development. However, its function during adulthood remains largely unknown. Here, we investigated whether the Hedgehog signaling pathway is active during adult life in Drosophila melanogaster, and we uncovered a protective function for Hedgehog signaling in coordinating correct proteostasis in glial cells. Adult-specific depletion of Hedgehog reduces lifespan, locomotor activity, and dopaminergic neuron integrity. Conversely, increased expression of Hedgehog extends lifespan and improves fitness. Moreover, Hedgehog pathway activation in glia rescues the lifespan and age-associated defects of hedgehog mutants. The Hedgehog pathway regulates downstream chaperones, whose overexpression in glial cells was sufficient to rescue the shortened lifespan and proteostasis defects of hedgehog mutants. Finally, we demonstrate the protective ability of Hedgehog signaling in a Drosophila Alzheimer's disease model expressing human amyloid beta in the glia. Overall, we propose that Hedgehog signaling is requisite for lifespan determination and correct proteostasis in glial cells.

Emerging Roles of Sonic Hedgehog in Adult Neurological Diseases: Neurogenesis and Beyond

Sonic hedgehog (Shh), a member of the hedgehog (Hh) family, was originally recognized as a morphogen possessing critical characters for neural development during embryogenesis. Recently, however, Shh has emerged as an important modulator in adult neural tissues through different mechanisms such as neurogenesis, anti-oxidation, anti-inflammation, and autophagy. Therefore, Shh may potentially have clinical application in neurodegenerative diseases and brain injuries. In this article, we present some examples, including ours, to show different aspects of Shh signaling and how Shh agonists or mimetics are used to alter the neuronal fates in various disease models, both in vitro and in vivo. Other potential mechanisms that are discussed include alteration of mitochondrial function and anti-aging effect; both are critical for age-related neurodegenerative diseases. A thorough understanding of the protective mechanisms elicited by Shh may provide a rationale to design innovative therapeutic regimens for various neurodegenerative diseases.

Activation of Sonic hedgehog signal by Purmorphamine, in a mouse model of Parkinson's disease, protects dopaminergic neurons and attenuates inflammatory response by mediating PI3K/AKt signaling pathway

In Parkinson's disease (PD), microglial activation-mediated neuroinflammation is associated with dopaminergic neurons degeneration in the substantia nigra pars compacta. Previous studies that have investigated this neurodegenerative disease have reported that the Sonic hedgehog (SHH) signaling pathway, through inhibiting the inflammatory processes, exerts a beneficial neuroprotective effect. However, the mechanisms underlying the anti-inflammatory and neuroprotective effects of this signaling pathway remain poorly understood. The present study aimed to further investigate these mechanisms in vitro and in vivo. At first, BV2 microglial cells treated with lipopolysaccharide (LPS) were used to induce an inflammatory response. It was observed that the activation of SHH signaling by Purmorphamine attenuated the LPS-induced inflammatory response, increased the expression of transforming growth factor-β1 through the phosphatidylinositol 3-kinase (PI3K)/AKT serine/threonine kinase (Akt) intracellular signaling pathway and inhibited nuclear receptor subfamily 4 group A member 2, independently of the PI3K/Akt signaling pathway. Furthermore, the blockade of the PI3K/Akt signaling pathway by intranasal administration of LY294002, significantly reduced the SHH-associated neuroprotective effects on dopaminergic neurons, improved motor functions, and increased the microglial activation and inflammatory response in a mouse model of PD induced using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. In conclusion, the data of the present study reported that anti-inflammatory and neuroprotective effects can be obtained in BV2 microglial cells and in a mouse model of PD by successive activation of the SHH and PI3K/Akt signaling pathways.

Targeting sonic hedgehog signaling in neurological disorders

Sonic hedgehog (Shh) signaling influences neurogenesis and neural patterning during the development of central nervous system. Dysregulation of Shh signaling in brain leads to neurological disorders like autism spectrum disorder, depression, dementia, stroke, Parkinson's diseases, Huntington's disease, locomotor deficit, epilepsy, demyelinating disease, neuropathies as well as brain tumors. The synthesis, processing and transport of Shh ligand as well as the localization of its receptors and signal transduction in the central nervous system has been carefully reviewed. Further, we summarize the regulation of small molecule modulators of Shh pathway with potential in neurological disorders. In conclusion, further studies are warranted to demonstrate the potential of positive and negative regulators of the Shh pathway in neurological disorders.

Resveratrol Pretreatment Decreases Ischemic Injury and Improves Neurological Function Via Sonic Hedgehog Signaling After Stroke in Rats

Resveratrol has neuroprotective effects for ischemic cerebral stroke. However, its neuroprotective mechanism for stroke is less well understood. Beneficial actions of the activated Sonic hedgehog (Shh) signaling pathway in stroke, such as improving neurological function, promoting neurogenesis, anti-oxidative, anti-apoptotic, and pro-angiogenic effects, have been noted, but relatively little is known about the role of Shh signaling in resveratrol-reduced cerebral ischemic injury after stroke. The present study tests whether the Shh pathway mediates resveratrol to decrease cerebral ischemic injury and improve neurological function after stroke. We observed that resveratrol pretreatment significantly improved neurological function, decreased infarct volume, enhanced vitality, and reduced apoptosis of neurons in vivo and vitro after stroke. Meanwhile, expression levels of Shh, Ptc-1, Smo, and Gli-1 mRNAs were significantly upregulated and Gli-1 was relocated to the nucleus. Intriguingly, in vivo and in vitro inhibition of the Shh signaling pathway with cyclopamine, a Smo inhibitor, completely reversed the above effects of resveratrol. These results suggest that decreased cerebral ischemic injury and improved neurological function by resveratrol may be mediated by the Shh signaling pathway.

Morphogens and blood-brain barrier function in health and disease

The microvasculature of the brain forms a protective blood-brain barrier (BBB) that ensures a homeostatic environment for the central nervous system (CNS), which is essential for optimal brain functioning. The barrier properties of the brain endothelial cells are maintained by cells surrounding the capillaries, such as astrocytes and pericytes. Together with the endothelium and a basement membrane, these supporting cells form the neurovascular unit (NVU). Accumulating evidence indicates that the supporting cells of the NVU release a wide variety of soluble factors that induce and control barrier properties in a concentration-dependent manner. The current review provides a comprehensive overview of how such factors, called morphogens, influence BBB integrity and functioning. Since impaired BBB function is apparent in numerous CNS disorders and is often associated with disease severity, we also discuss the potential therapeutic value of these morphogens, as they may represent promising therapies for a wide variety of CNS disorders.