Inhibition of GPR17/ID2 Axis Improve Remyelination and Cognitive Recovery after SAH by Mediating OPC Differentiation in Rat Model.

Myelin sheath injury contributes to cognitive deficits following subarachnoid hemorrhage (SAH). G protein-coupled receptor 17 (GPR17), a membrane receptor, negatively regulates oligodendrocyte precursor cell (OPC) differentiation in both developmental and pathological contexts. Nonetheless, GPR17's role in modulating OPC differentiation, facilitating remyelination post SAH, and its interaction with downstream molecules remain elusive. In a rat SAH model induced by arterial puncture, OPCs expressing GPR17 proliferated prominently by day 14 post-onset, coinciding with compromised myelin sheath integrity and cognitive deficits. Selective Gpr17 knockdown in oligodendrocytes (OLs) via adeno-associated virus (AAV) administration revealed that reduced GPR17 levels promoted OPC differentiation, restored myelin sheath integrity, and improved cognitive deficits by day 14 post-SAH. Moreover, GPR17 knockdown attenuated the elevated expression of the inhibitor of DNA binding 2 (ID2) post-SAH, suggesting a GPR17-ID2 regulatory axis. Bi-directional modulation of ID2 expression in OLs using AAV unveiled that elevated ID2 counteracted the restorative effects of GPR17 knockdown. This resulted in hindered differentiation, exacerbated myelin sheath impairment, and worsened cognitive deficits. These findings highlight the pivotal roles of GPR17 and ID2 in governing OPC differentiation and axonal remyelination post-SAH. This study positions GPR17 as a potential therapeutic target for SAH intervention. The interplay between GPR17 and ID2 introduces a novel avenue for ameliorating cognitive deficits post-SAH.

TREM2 activation alleviates neural damage via Akt/CREB/BDNF signalling after traumatic brain injury in mice.

BACKGROUND: Neuroinflammation is one of the most important processes in secondary injury after traumatic brain injury (TBI). Triggering receptor expressed on myeloid cells 2 (TREM2) has been proven to exert neuroprotective effects in neurodegenerative diseases and stroke by modulating neuroinflammation, and promoting phagocytosis and cell survival. However, the role of TREM2 in TBI has not yet been elucidated. In this study, we are the first to use COG1410, an agonist of TREM2, to assess the effects of TREM2 activation in a murine TBI model. METHODS: Adult male wild-type (WT) C57BL/6 mice and adult male TREM2 KO mice were subjected to different treatments. TBI was established by the controlled cortical impact (CCI) method. COG1410 was delivered 1 h after CCI via tail vein injection. Western blot analysis, immunofluorescence, laser speckle contrast imaging (LSCI), neurological behaviour tests, brain electrophysiological monitoring, Evans blue assays, magnetic resonance imaging (MRI), and brain water content measurement were performed in this study. RESULTS: The expression of endogenous TREM2 peaked at 3 d after CCI, and it was mainly expressed on microglia and neurons. We found that COG1410 improved neurological functions within 3 d, as well as neurological functions and brain electrophysiological activity at 2 weeks after CCI. COG1410 exerted neuroprotective effects by inhibiting neutrophil infiltration and microglial activation, and suppressing neuroinflammation after CCI. In addition, COG1410 treatment alleviated blood brain barrier (BBB) disruption and brain oedema; furthermore, COG1410 promoted cerebral blood flow (CBF) recovery at traumatic injury sites after CCI. In addition, COG1410 suppressed neural apoptosis at 3 d after CCI. TREM2 activation upregulated p-Akt, p-CREB, BDNF, and Bcl-2 and suppressed TNF-α, IL-1ß, Bax, and cleaved caspase-3 at 3 d after CCI. Moreover, TREM2 knockout abolished the effects of COG1410 on vascular phenotypes and microglial states. Finally, the neuroprotective effects of COG1410 were suppressed by TREM2 depletion. CONCLUSIONS: Altogether, we are the first to demonstrate that TREM2 activation by COG1410 alleviated neural damage through activation of Akt/CREB/BDNF signalling axis in microglia after CCI. Finally, COG1410 treatment improved neurological behaviour and brain electrophysiological activity after CCI.

Hydrazine Formation via Coupling of a Nickel(III)-NH2 Radical.

M(NHx ) intermediates involved in N-N bond formation are central to ammonia oxidation (AO) catalysis, an enabling technology to ultimately exploit ammonia (NH3 ) as an alternative fuel source. While homocoupling of a terminal amide species (M-NH2 ) to form hydrazine (N2 H4 ) has been proposed, well-defined examples are without precedent. Herein, we discuss the generation and electronic structure of a NiIII -NH2 species that undergoes bimolecular coupling to generate a NiII 2 (N2 H4 ) complex. This hydrazine adduct can be further oxidized to a structurally unusual Ni2 (N2 H2 ) species; this releases N2 in the presence of NH3 , thus establishing a synthetic cycle for Ni-mediated AO. Distribution of the redox load for H2 N-NH2 formation via NH2 coupling between two metal centers presents an attractive strategy for AO catalysis using Earth-abundant, late first-row metals.

Chromogranin A (CGA)-derived polypeptide (CGA47-66) inhibits TNF-α-induced vascular endothelial hyper-permeability through SOC-related Ca2+ signaling.

CGA1-78 (Vasostatin-1, VS-1) a N-terminal Chromogranin A (CGA)-derived peptide, has been shown to have a protective effect against TNF-α-induced impairment of endothelial cell integrity. However, the mechanisms of this effect have not yet been clarified. CGA47-66 (Chromofungin, CHR) is an important bioactive fragment of CGA1-78. The present study aims to explore the protective effects of CHR on the vascular endothelial cell barrier response to TNF-α and its related Ca2+ signaling mechanisms. EA.hy926 cells were used as a vascular endothelial culture model. The synthetic peptides CHR and CGA4-16 were assessed for their ability to suppress TNF-α-induced EA.hy926 cells hyper-permeability through Transwell® and TEER assays. Changes in [Ca2+]i were measured through confocal laser scanning microscopy. SOC channel currents (Isoc) were measured via patch-clamp analysis. RT-PCR and western blot were used to analyze mRNA and protein expression of the transient receptor potential channels TRPC1 and TRPC4, respectively. FITC and rhodamine-phalloidin fluorescence were used to assess cell morphology and the distribution of MyPT-1 and F-actin. Compared to untreated cells, TNF-α increased the permeability of EA.hy926 cells that was inhibited by pre-treatment with CHR (10-1000 nM) in concentration-dependent manner, and the effect was most obvious at 100 nM, but CGA4-16 (100 nM) had no effect. TNF-α treatment increased the phosphorylation of MyPT-1 and stress fiber formation. CHR (10-1000 nM) pretreatment inhibited the cytoskeletal rearrangements and increased [Ca2+]i in response to TNF-α treatment. CHR also reduced TRPC1 expression following TNF-α induction. Similar to SOC inhibitor 2-APB, CHR suppressed IP3 mediated SOC activation. These findings suggest that CHR inhibits TNF-α-induced Ca2+ influx and protects the barrier function of vascular endothelial cells, and that these effects are related to the inhibition of SOC and Ca2+ signaling by CHR.

An S = 1/2 Iron Complex Featuring N2, Thiolate, and Hydride Ligands: Reductive Elimination of H2 and Relevant Thermochemical Fe-H Parameters.

Believed to accumulate on the Fe sites of the FeMo-cofactor (FeMoco) of MoFe-nitrogenase under turnover, strongly donating hydrides have been proposed to facilitate N2 binding to Fe and may also participate in the hydrogen evolution process concomitant to nitrogen fixation. Here, we report the synthesis and characterization of a thiolate-coordinated FeIII(H)(N2) complex, which releases H2 upon warming to yield an FeII-N2-FeII complex. Bimolecular reductive elimination of H2 from metal hydrides is pertinent to the hydrogen evolution processes of both enzymes and electrocatalysts, but well-defined examples are uncommon and usually observed from diamagnetic second- and third-row transition metals. Kinetic data obtained on the HER of this ferric hydride species are consistent with a bimolecular reductive elimination pathway, arising from cleavage of the Fe-H bond with a computationally determined BDFE of 55.6 kcal/mol.

Anti-inflammatory mechanism of ulinastatin: Inhibiting the hyperpermeability of vascular endothelial cells induced by TNF-α via the RhoA/ROCK signal pathway.

OBJECTIVE: Ulinastatin reduces the high permeability of vascular endothelial cells induced by tumor necrosis factor alpha (TNF-α). This study investigated the molecular mechanism behind this effect, with the aim of understanding the action of ulinastatin in sepsis therapy and exploring novel therapeutic strategies for sepsis patients. METHODS: A TNF-α treated human umbilical vein endothelial cell line (EA.hy926) was employed as an inflammation model. Horseradish peroxidase permeability assays and an epithelial voltmeter method were used to measure the permeability of EA.hy926 cells. Immunocytochemistry was used to assay the expression of p-MYPT1 and the distribution and morphology of F-actin; the expression of the key molecules related to vascular endothelial permeability (RhoA, ROCK2, MYPT1, p-MYPT1 and VE-cadherin) was detected by immunocytochemistry assays, western blotting and quantitative real-time polymerase chain reaction. RESULTS: After incubation with TNF-α or septic serum, the transendothelial electrical resistance of EA.hy926 cells decreased and the permeability of the cells increased significantly (all P<0.05). The expression of p-MYPT1 was higher and VE-cadherin was lower compared with the control group, and F-actin was redistributed, with the formation of additional stress fibers in the cells. Ulinastatin treatment moderated these phenomena. The immunocytochemistry assays and western blots showed that the expression of RhoA and ROCK2 was significantly upregulated in cells treated with TNF-α (P<0.05); however, ulinastatin could inhibit the high expression of these two proteins. Under treatment with TNF-α and ulinastatin, compared with normal EA.hy926 cells, overexpression of RhoA upregulated expression of RhoA, ROCK2 and p-MYPT1, downregulated expression of VE-cadherin, and restored the hyperpermeability of vascular endothelial cells due to TNF-α treatment (P<0.05). CONCLUSIONS: Ulinastatin inhibited the hyperpermeability of vascular endothelial cells induced by TNF-α. This inhibitory effect of ulinastatin may be related to the RhoA/ROCK signaling pathway.

[A study of inhibitory effect of chromogranin A derived peptide CGA(47 _ 66) on hyper - permeability of endothelium induced by serum of septic patient].

OBJECTIVE: To explore the role of chromogranin A ( CGA) derived peptide CGA47~ ( Chromfungin, CHR) on septic serum induced high permeability of vascular endothelial cells. METHODS: Human umbilical venous endothelial cell line (EA.hy926 cells) was exposed to CHR, serum of septic shock patient, and tumor necrosis factor-a (TNF-a) respectively. Methyl thiazolyl tetrazolium (MTT) method, Transwell assay and immunofluorescence were performed to determine cell viability (absorbance (A) value J, permeability of monolayer endothelial cells (A value) , and the morphological characteristic and distribution ofF -actin respectively. RESULTS: Compared with the blank control group, when EA.hy926 were exposed to CHR with 1, 10, 100 nmol/L the cell activity was not significantly affected (A value: 1.219 ± 0.253, 1.179 ± 0.065, 1.179 ± 0.062 vs. 1.306 ± 0.162, all P>0.05), while when the cells was exposed to CHR in 1 000 nmol/L the cell activity was significantly inhibited (A value: 1.049 ± 0.256 vs. 1.306 ± 0.162, t=-2.390, P=0.031 ). Compared with blank control group, when the cells were exposed to CHR of 1, 10, 100 nmol/L a significant decrease in permeability in EA.hy926 cells was observed (A value: 1.619 ± 0.324, 1.496 ± 0.356, 1.132 ± 0.280 vs. 2.315 ± 0.440, P<0.05 or P<0.01 ). Treatment of septic shock patient's serum or TNF-a to EA. hy926 produced an obvious increase in its permeability (septic serum group A value: 1.204 ± 0.248 vs. 0.277 ± 0.017, P<0.01; TNF-a group A value: 2.485 ± 0.113 vs. 1.602 ± 0.679, P<0.05). High-permeability induced by TNF-a or septic shock patient's serum was alleviated hy CHR in the concentration of 1, 10, 100 nmol/L in a dose-dependent manner (septic serum + CHR group A value: 0.299 ± 0.065, 0.224 ± 0.028, 0.131 ± 0.015 vs. 1.204 ± 0.248; TNF -a + CHR group A value: 1.995 ± 0.394, 1.920 ± 0.096, 1.744 ± 0.475 vs. 2.485 ± 0.113, P<0.05 or P<0.01 ). Under a laser scanning confocal microscope, it was found that the F-actin cytoskeleton of EA.hy926 cells was redistributed, and more stress fibers were found in the septic shock patient's serum group and TNF-α group, while CHR obviously alleviated the above effects induced by septic shock patient's serum or TNF-α. CONCLUSION: In a dose-dependent manner, CHR may inhibit increased permeability of vascular endothelial cells induced by septic shock patient's serum, its underlying mechanism may be related to inhibition of the effect of TNF-α.