The role of SUMO specific peptidase 3 in secondary inflammation of ischemic stroke in mice.

Ischemic stroke is the main cause of death and disability, and microglia play a crucial role in the pathophysiology of hypoxic ischemic brain injury. We found that SENP3 is highly expressed in the early stages of ischemic stroke in both in vivo and in vitro mouse models, and may be related to the deSUMOylation of the key kinase MKK7 in the TLR4/p-JNK signaling pathway. Knocking down SENP3 can inhibit the deSUMOylation of MKK7, thereby inhibiting the activation of the TLR4/p-JNK signaling pathway in an in vitro stroke model. Proteomic analysis showed that SENP3 undergoes phosphorylation at the T429 site after ischemic stroke. Computer simulation predictions show a significant enhancement of the interaction between pT429-SENP3 and MKK7, which has been confirmed through experiments on the interaction of biological macromolecules (SPR). The mitochondrial metabolic abnormalities caused by energy abnormalities in the early stages of stroke provide a good explanation for the phosphorylation of SENP3. Therefore, we used the mitochondrial complex inhibitor TTFA to reverse demonstrate that the phosphorylation of SENP3 comes from the large amount of adenosine triphosphate produced by mitochondrial abnormal metabolism caused by early oxygen glucose deficiency. Finally, proteomic analysis indicates that a significant amount of oxidative phosphorylation does occur in the early stages of stroke. In summary, targeted regulation of SENP3 phosphorylation to affect the deSUMOylation of MKK7 may inhibit secondary inflammation in ischemic stroke.

Mesenteric Neural Crest Cells Are the Embryological Basis of Skip Segment Hirschsprung's Disease.

BACKGROUND & AIMS: Defective rostrocaudal colonization of the gut by vagal neural crest cells (vNCCs) results in Hirschsprung's disease (HSCR), which is characterized by aganglionosis in variable lengths of the distal bowel. Skip segment Hirschsprung's disease (SSHD), referring to a ganglionated segment within an otherwise aganglionic intestine, contradicts HSCR pathogenesis and underscores a significant gap in our understanding of the development of the enteric nervous system. Here, we aimed to identify the embryonic origin of the ganglionic segments in SSHD. METHODS: Intestinal biopsy specimens from HSCR patients were prepared via the Swiss-roll technique to search for SSHD cases. NCC migration from the neural tube to the gut was spatiotemporally traced using targeted cell lineages and gene manipulation in mice. RESULTS: After invading the mesentery surrounding the foregut, vNCCs separated into 2 populations: mesenteric NCCs (mNCCs) proceeded to migrate along the mesentery, whereas enteric NCCs invaded the foregut to migrate along the gut. mNCCs not only produced neurons and glia within the gut mesentery, but also continuously complemented the enteric NCC pool. Two new cases of SSHD were identified from 183 HSCR patients, and Ednrb-mutant mice, but not Ret-/- mice, showed a high incidence rate of SSHD-like phenotypes. CONCLUSIONS: mNCCs, a subset of vNCCs that migrate into the gut via the gut mesentery to give rise to enteric neurons, could provide an embryologic explanation for SSHD. These findings lead to novel insights into the development of the enteric nervous system and the etiology of HSCR.

Mapping of Extrinsic Innervation of the Gastrointestinal Tract in the Mouse Embryo.

Precise extrinsic afferent (visceral sensory) and efferent (sympathetic and parasympathetic) innervation of the gut is fundamental for gut-brain cross talk. Owing to the limitation of intrinsic markers to distinctively visualize the three classes of extrinsic axons, which intimately associate within the gut mesentery, detailed information on the development of extrinsic gut-innervating axons remains relatively sparse. Here, we mapped extrinsic innervation of the gut and explored the relationships among various types of extrinsic axons during embryonic development in mice. Visualization with characterized intrinsic markers revealed that visceral sensory, sympathetic, and parasympathetic axons arise from different anatomic locations, project in close association via the gut mesentery, and form distinctive innervation patterns within the gut from embryonic day (E)10.5 to E16.5. Genetic ablation of visceral sensory trajectories results in the erratic extension of both sympathetic and parasympathetic axons, implicating that afferent axons provide an axonal scaffold to route efferent axons. Coculture assay further confirmed the attractive effect of sensory axons on sympathetic axons. Taken together, our study provides key information regarding the development of extrinsic gut-innervating axons occurring through heterotypic axonal interactions and provides an anatomic basis to uncover neural circuit assembly in the gut-brain axis (GBA).SIGNIFICANCE STATEMENT Understanding the development of extrinsic innervation of the gut is essential to unravel the bidirectional neural communication between the brain and the gut. Here, with characterized intrinsic markers targeting vagal sensory, spinal sensory, sympathetic, and parasympathetic axons, respectively, we comprehensively traced the spatiotemporal development of extrinsic axons to the gut during embryonic development in mice. Moreover, in line with the somatic nervous system, pretarget sorting via heterotypic axonal interactions is revealed to play critical roles in patterning extrinsic efferent trajectories to the gut. These findings provide basic anatomic information to explore the mechanisms underlying the process of assembling neural circuitry in the gut-brain axis (GBA).

Dopamine neuron loss by selective deletion of autophagy-related gene 5 is not exacerbated by MPTP toxicity in midbrain.

Parkinson's disease (PD) is a progressive neurological disease, one of the pathological characteristics is a gradual loss of midbrain dopaminergic (mDA) neurons in the substantia nigra pars compacta (SNpc). In animals, PD-like symptoms can be induced by genetic mutations or by neurotoxins such as 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP). It has been reported that deletion of autophagy-related gene 5 (Atg5) in the brain can disrupt neural function and is accompanied by the accumulation of cytoplasmic inclusions. However, the exact role of autophagy in PD etiology has not fully been asserted. In this study, we used tyrosine hydroxylase (TH)-Cre mice to generate conditional knockouts (CKO) with the specific deletion of Atg5 in mDA neurons, and found that adult Atg5 CKO mice contained ubiquitin- and p62-positive inclusions and fewer TH-positive mDA neurons compared with wild-type controls. Interestingly, MPTP-induced loss of mDA neurons was not observed in Atg5 CKO mice. Thus, Atg5-associated autophagy is required for the survival of mDA neurons, and may be involved in MPTP-induced neuronal degeneration.

Oxytocin is implicated in social memory deficits induced by early sensory deprivation in mice.

Early-life sensory input plays a crucial role in brain development. Although deprivation of orofacial sensory input at perinatal stages disrupts the establishment of the barrel cortex and relevant callosal connections, its long-term effect on adult behavior remains elusive. In this study, we investigated the behavioral phenotypes in adult mice with unilateral transection of the infraorbital nerve (ION) at postnatal day 3 (P3). Although ION-transected mice had normal locomotor activity, motor coordination, olfaction, anxiety-like behaviors, novel object memory, preference for social novelty and sociability, they presented deficits in social memory and spatial memory compared with control mice. In addition, the social memory deficit was associated with reduced oxytocin (OXT) levels in the hypothalamus and could be partially restored by intranasal administration of OXT. Thus, early sensory deprivation does result in behavioral alterations in mice, some of which may be associated with the disruption of oxytocin signaling.

Deletion of autophagy-related gene 7 in dopaminergic neurons prevents their loss induced by MPTP.

Parkinson's disease (PD) is a neurodegenerative disease caused by a gradual loss of midbrain dopaminergic (mDA) neurons in the substantia nigra pars compacta (SNpc) during aging. 1-Methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) is one of the neurotoxins used widely to induce PD-like symptoms in PD animal models, including rodents and non-human primates. It has been reported that deletion of autophagy-related gene 7 (Atg7) in the brain results in a reduction of mDA neurons in adulthood. In this study, we used tyrosine hydroxylase (TH)-Cre mice to generate conditional knockout (CKO) mice with the specific deletion of Atg7 in mDA neurons. Consistent with previous reports, adult Atg7 CKO mice contained fewer TH-positive mDA neurons compared with wild-type (WT) controls. TH-expressing neurons containing puncta-like structures with p62 and ubiquitin immunoreactivity were observed in the midbrain of Atg7 CKO mice but were not detected in control mice. However, MPTP-induced loss of mDA neurons was not observed in Atg7 CKO mice. Our results indicate that Atg7-involved autophagy is required not only for the survival of mDA neurons in the mouse brain, but also for MPTP-induced mDA neuron degeneration.

Evaluation of blood-brain barrier permeability in tryptophan hydroxylase 2-knockout mice.

The blood-brain barrier (BBB) is critical to the health of the central nervous system (CNS). The possibility that 5-hydroxytryptamine (5-HT) participates in the alteration of the BBB has been previously demonstrated. Tryptophan hydroxylase 2 (TPH2) is a unique genetic enzyme isoform that catalyzes the rate-limiting step in the biosynthesis of 5-HT in the CNS; however, its role in the permeability changes of the BBB remains unclear. In the present study, TPH2-knockout mice were utilized in the assessment of BBB disruption, as measured by the Evans Blue (EB) extravasation or fluorescein isothiocyanate-albumin leakage assay in the brain. EB was not found to be retained in the brain in the TPH2-knockout mice or the wild-type controls. The results of the study demonstrate that TPH2 knockout has no effect on BBB permeability, indicating that TPH2 and the 5-HT system in the CNS are not sufficient to influence the BBB leakage.

Depletion of canonical Wnt signaling components has a neuroprotective effect on midbrain dopaminergic neurons in an MPTP-induced mouse model of Parkinson's disease.

The canonical Wnt signaling pathway is critical for the development of midbrain dopaminergic (DA) neurons, and recent studies have suggested that disruption of this signaling cascade may underlie the pathogenesis of Parkinson's disease (PD). However, the exact role of the canonical Wnt signaling pathway, including low-density lipoprotein receptor-related protein 5 and 6 (LRP5/6) and ß-catenin components, in a mouse model of PD remains unclear. In the present study, the tyrosine hydroxylase (TH)-Cre transgenic mouse line was used to generate mice with the specific knockout of LRP5, LRP6 or ß-catenin in DA neurons. Following inactivation of LRP5, LRP6 or ß-catenin, TH-immunohistochemical staining was performed. The results indicated that ß-catenin is required for the development or maintenance of these neurons; however, LRP5 and LRP6 were found to be dispensable. In 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice, the depletion of LRP5, LRP6 or ß-catenin was found to be protective for the midbrain DA neurons to a certain extent. These in vivo results provide a novel perspective for the function of the canonical Wnt signaling pathway in a mouse model of PD.