Sonic Hedgehog Signaling Promotes Peri-Lesion Cell Proliferation and Functional Improvement after Cortical Contusion Injury

Ablated Sonic Hedgehog Signaling in the Dentate Gyrus of the Dorsal and Ventral Hippocampus Impairs Hippocampal-Dependent Memory Tasks and Emotion in a Rat Model of Depression

Specific memory processes and emotional aberrations in depression can be attributed to the different dorsal-ventral regions of the hippocampus. However, the molecular mechanisms underlying the differential functions of the dorsal hippocampus (dHip) and ventral hippocampus (vHip) remain unclear. As Sonic Hedgehog (Shh) is involved in the dorsal-ventral patterning of the neural tube and its signaling is dysregulated by chronic unpredictable mild stress (CUMS), we investigated its role in influencing the differential functions of the dHip and vHip. Here, CUMS downregulated the expression of Shh signaling markers, including Shh and its downstream effectors GLI family zinc finger 12 (Gli1/2), Patched (Ptch), and smoothened (Smo), in both the dHip and vHip of rats, though more so in the vHip. Additionally, Shh knockdown in the dorsal or ventral dentate gyrus (DG) resulted in restrained neurogenic activity in newborn neurons, especially in immature neurons through decreased expression of Shh signaling markers. Furthermore, Shh knockdown in the DG of the dHip led to memory impairment by inhibiting experience-dependent activation of immature neurons, whereas its knockdown in the DG of the vHip led to an emotional handicap by delaying the maturation of immature neurons. Finally, Shh knockdown in either the dDG or vDG of hippocampus abolished the corresponding cognitive enhancement and emotional recovery of fluoxetine. In conclusion, Shh is essential to maintain the functional heterogeneity of dHip and vHip in depressed rat, which was mainly mediating by local changes of dependent activation and maturity of immature neurons, respectively.

Roles of astrocytic sonic hedgehog production and its signal for regulation of the blood-brain barrier permeability

Sonic hedgehog (Shh) is a secreted glycopeptide belonging to the hedgehog family that is essential for morphogenesis during embryonic development. The Shh signal is mediated by two membrane proteins, Patched-1 (Ptch-1) and Smoothened (Smo), following the activation of transcription factors such as Gli. Shh decreases the permeability of the blood-brain barrier (BBB) and plays a key role in its function. In the damaged brain, BBB function is remarkably disrupted. The BBB disruption causes brain edema and neuroinflammation resulting from the extravasation of serum components and the infiltration of inflammatory cells into the cerebral parenchyma. Multiple studies have suggested that astrocyte is a source of Shh and that astrocytic Shh production is increased in the damaged brain. In various experimental animal models of acute brain injury, Shh or Shh signal activators alleviate BBB disruption by increasing tight junction proteins in endothelial cells. Furthermore, activation of astrocytic Shh signaling reduces reactive astrogliosis, neuroinflammation, and increases the production of vascular protective factors, which alleviates BBB disruption in the damaged brain. These findings suggest that astrocytic Shh and Shh signaling protect BBB function in the damaged brain and that target drugs for Shh signaling are expected to be novel therapeutic drugs for acute brain injuries.

LncRNA CRNDE binds hnRNPA1 to facilitate carbon monoxide poisoning-induced delayed encephalopathy via inhibiting UCHL5-mediated SMO deubiquitination

Delayed encephalopathy after acute carbon monoxide poisoning (DEACMP) is one of the most common complications following carbon monoxide intoxication. Long noncoding RNAs (lncRNAs) exert critical functions in numerous neurological disorders. We intended to investigate the role of CRNDE in DEACMP. The DEACMP model in rats and the oxygen-glucose deprivation/reoxygenation (OGD/R) model in PC-12 cells were established. Brain and cell injuries were assessed with H&E staining, Nissl staining, TUNEL and CCK8 assays, respectively. Related proteins and RNAs were quantified with western blot and qRT-PCR. The N6-methyladenosine (m6A) level was determined using MeRIP-qPCR and immunofluorescence. Loss and gain function studies were performed to investigate the biological function of CRNDE. The potential mechanisms between each factor were explored using RNA immunoprecipitation, RNA-pull down and co-immunoprecipitation. CRNDE was increased in the hippocampal tissues of DEACMP rats and in OGD/R-treated PC-12 cells, which was positively correlated to m6A modification. Knockdown of CRNDE reduced cell damage and elevated UCHL5 and SMO expressions in OGD/R-treated PC-12 cells. hnRNPA1 was upregulated in DEACMP. In addition, inhibiting hnRNPA1 prevented apoptosis in PC-12 cells subjected to OGD/R. hnRNPA1 bound to CRNDE and remained in the nucleus, which inhibited UCHL5 expression through the formation of CRNDE-hnRNPA1-mRNA complex. UCHL5 could inhibit SMO ubiquitination and suppress PC-12 cell apoptosis during OGD/R. CRNDE silencing blocked brain injury in DEACMP, while knocking down UCHL5 reversed these effects. CRNDE interacted with hnRNPA1 to facilitate DEACMP via inhibition of UCHL5-mediated SMO deubiquitination. CRNDE might be a latent therapeutic target for treating DEACMP.

GIMAP7 induces oxidative stress and apoptosis of ovarian granulosa cells in polycystic ovary syndrome by inhibiting sonic hedgehog signalling pathway

Polycystic ovary syndrome (PCOS) is a gynaecological endocrine disease. The objective of the present study was to investigate the role of GTPase immunity-associated protein (GIMAP) 7 in PCOS. A PCOS rat model was established using dehydroepiandrosterone injection. The data showed that GIMAP7 was mainly located in granulosa cells and was abundantly expressed in the ovarian granulosa cells of PCOS rats. GIMAP7 silencing decreased blood glucose levels, HOMA-IR scores, and number of cystic follicles. In addition, GIMAP7 silencing corrected erratic oestrous cycles, inhibited apoptosis and reduced c-caspase-3 protein expression in the ovarian tissues of PCOS rats. GIMAP7 silencing reduced malondialdehyde (MDA) but increased glutathione (GSH) and superoxide dismutase (SOD) levels in the serum and ovarian tissues of PCOS rats. The effects of GIMAP7 were further investigated in human ovarian granulosa KGN cells. GIMAP7 silencing increased the viability, promoted proliferation, and increased the percentage of S-phase KGN cells. The apoptosis rate was significantly decreased by GIMAP7 silencing. GIMAP7 also inhibited oxidative stress in KGN cells, resulting in decreased levels of reactive oxygen species (ROS) and MDA and increased levels of GSH and SOD. Notably, GIMAP7 inhibited the sonic hedgehog (SHH) signalling pathway, and GIMAP7 silencing increased the expression of the SHH signalling pathway downstream genes SHH, SMO, and Gli1. Inhibition of the SHH signalling pathway using cyclopamine reduced the effect of GIMAP7 silencing on KGN cells. This study proved that GIMAP7 promotes oxidative stress and apoptosis in ovarian granulosa cells in PCOS by inhibiting the SHH signalling pathway.

New Tricks for an Old (Hedge)Hog: Sonic Hedgehog Regulation of Astrocyte Function

The Sonic hedgehog (Shh) molecular signaling pathway is well established as a key regulator of neurodevelopment. It regulates diverse cellular behaviors, and its functions vary with respect to cell type, region, and developmental stage, reflecting the incredible pleiotropy of this molecular signaling pathway. Although it is best understood for its roles in development, Shh signaling persists into adulthood and is emerging as an important regulator of astrocyte function. Astrocytes play central roles in a broad array of nervous system functions, including synapse formation and function as well as coordination and orchestration of CNS inflammatory responses in pathological states. Neurons are the source of Shh in the adult, suggesting that Shh signaling mediates neuron-astrocyte communication, a novel role for this multifaceted pathway. Multiple roles for Shh signaling in astrocytes are increasingly being identified, including regulation of astrocyte identity, modulation of synaptic organization, and limitation of inflammation. This review discusses these novel roles for Shh signaling in regulating diverse astrocyte functions in the healthy brain and in pathology.