Hypertension is one of the major predisposing factors for neurodegenerative disease characterized with activated renin-angiotensin system (RAS) in both periphery and brain. Vitamin D (VitD) is recently recognized as a pleiotropic hormone with strong neuroprotective properties. While multiple lines of evidence suggest that VitD can act on RAS, the evidence concerning the crosstalk between VitD and RAS in the brain is limited. Therefore, this study aims to evaluate whether VitD can modulate brain RAS to trigger neuroprotective actions in the brain of spontaneously hypertensive rats (SHR). Our data showed that calcitriol treatment induced VDR expression and inhibited neural death in the prefrontal cortex of SHR. Sustained calcitriol administration also inhibited microglia M1 polarization, but enhanced M2 polarization, accompanied with decreased expression of proinflammatory cytokines. We then further explored the potential mechanisms and showed that SHR exhibited overactivated classical RAS with increased expression of angiotensin II (Ang II) receptor type 1 (AT1), angiotensin converting enzyme (ACE) and Ang II production, whereas the counteracting arm of traditional RAS, ACE2/Ang(1–7)/MasR, was impaired in the SHR brain. Calcitriol nonsignificantly suppressed AT1 and ACE but markedly reduced Ang II formation. Intriguingly, calcitriol exerted pronouncedly impact on ACE2/Ang(1–7)/MasR axis with enhanced expression of ACE2, MasR and Ang(1–7) generation. Meanwhile, calcitriol ameliorated the overactivation of NADPH-oxidase (Nox), the downstream of RAS, in SHR, and also mitigated oxidative stress. In microglial (BV2) cells, we further found that calcitriol induced ACE2 and MasR with no significant impact on ACE and AT1. In accordance, calcitriol also attenuated Ang II-induced Nox activation and ROS production, and shifted the microglia polarization from M1 to M2 phenotype. However, co-treatment with A779, a specific MasR antagonist, abrogated the antioxidant and neuroimmune modulating actions of VitD. These findings strongly indicate the involvement of ACE2/Ang(1–7)/MasR pathway in the neuroprotective mechanisms of VitD in the hypertensive brain.

Traumatic brain injury (TBI) is a leading cause of mortality and disability in children and young adults worldwide. Neurologic impairment is caused by both immediate brain tissue disruption and post-injury cellular and molecular events that worsen the primary neurologic insult. The β-lactam antibiotic ceftriaxone (CTX) has been reported to induce neuroprotection in animal models of diverse neurologic diseases via up-regulation of GLT-1. However, no studies have addressed the neuroprotective role of CTX in the setting of TBI, and whether the mechanism is involved in the modulation of neuronal autophagy remains totally unclear. The present study was designed to determine the hypothesis that administration of CTX could significantly enhance functional recovery in a rat model of TBI and whether CTX treatment could up-regulate GLT-1 expression and suppress post-TBI neuronal autophagy. The results demonstrated that daily treatment with CTX attenuated TBI-induced brain edema and cognitive function deficits in rats. GLT-1 is down-regulated following TBI and this phenomenon can be reversed by treatment of CTX. In addition, we also found that CTX significantly reduced autophagy marker protein, LC3 II, in hippocampus compared to the TBI group. These results suggest that CTX might provide a new therapeutic strategy for TBI and this protection might be associated with up-regulation of GLT-1 and suppression of neuronal autophagy.

Accumulating evidence indicates that autophagy and inflammatory responses contributes to secondary brain injury after traumatic brain injury (TBI), and toll-like receptor 4 (TLR4) is considered to involvement of this cascade and plays an important role. The present study was designed to determine the hypothesis that administration of resatorvid (TAK-242), a TLR4 antagonist, might provide a neuroprotective effect by inhibit TLR4-mediated pathway in a TBI rat model. Rat subjected to controlled cortical impact injury were injected with TAK-242 (0.5 mg/kg, i.v. injected) 10 min prior to injury. The results demonstrated that TAK-242 treatment significantly attenuated TBI-induced neurons loss, brain edema, and neurobehavioral impairment in rats. Immunoblotting analysis showed that TAK-242 treatment reduced TBI-induced TLR4, Beclin 1, and LC3-II levels, and maintained p62 levels at 24 h. Double immunolabeling demonstrated that LC3 dots co-localized with the hippocampus pyramidal neurons, and TLR4 was localized with the hippocampus neurons and astrocytes. In addition, the expression of TLR4 downstream signaling molecules, including MyD88, TRIF, NF-κB, TNF-α, and IL-1β, was significantly downregulated in hippocampus tissue by Western blot analysis. In conclusion, our findings indicate that pre-injury treatment with TAK-242 could inhibit neuronal autophagy and neuroinflammation responses in the hippocampus in a rat model of TBI. The neuroprotective effects of TAK-242 may be related to modulation of the TLR4-MyD88/TRIF-NF-κB signaling pathway. Furthermore, the study also suggests that TAK-242, an attractive potential drug, may be a promising drug candidate for TBI.

Neuronal autophagy and inflammatory responses are important in the pathogenesis of traumatic brain injury (TBI), and toll-like receptor 4 (TLR4) may play an important role in the related molecular cascade. The present study investigated the protective effect of apocynin, an inhibitor of NADPH oxidase, in a TBI rat model and further examined neuronal autophagy and the TLR4-mediated pathway. Adult male Sprague-Dawley rats were subjected to controlled cortical impact injury and intraperitoneally injected with apocynin (50 mg/kg) immediately after the trauma. In addition to motor and behavioral studies, brain water content and histology analyses were performed. Expression of autophagy-related proteins as well as TLR4/NF-κB signaling and inflammatory mediators was analyzed. The apocynin treatment significantly attenuated TBI-induced motor and behavioral impairment, brain edema and neuronal damage in rats. Immunohistochemical and Western blot analyses revealed that apocynin treatment significantly reduced the expression of NOX, LC3 and Beclin1 in the hippocampus at 12-48 h after injury. Double immunolabeling demonstrated that apocynin decreased the co-localization of LC3 or TLR4-positive cells with hippocampal neurons at 24 h following TBI. In addition, CD11b (microglial marker) and GFAP (astrocyte marker)-immunopositive cells were also clearly decreased in hippocampal tissues. Meanwhile, protein levels of TLR4, NF-κB p65, TNF-α and IL-1β were found to be significantly downregulated by Western blot analysis. In conclusion, our findings indicate that the protective effects of apocynin may be related to modulation of neuronal autophagy and the TLR4/NF-κB signaling pathway.

Clozapine (CLO) remains an ultimate option for patients with treatment resistant schizophrenia. However, the atypical antipsychotic is often associated with serious metabolic side effects, such as dyslipidemia. Hepatic sterol regulatory element-binding proteins (SREBPs) are central in the allosteric control of a variety of lipid biosynthetic pathways. There is emerging evidence that CLO can activate SREBP pathway and enhance downstream lipogenesis, whereas curcumin (CUR), a major active compound of Curcuma longa, contains hypolipidemic properties. Therefore, in the present study, we examined the protective effects of CUR against CLO-induced lipid disturbance and analyzed the expression of key components in hepatic lipid metabolism. Our data showed that 4-week treatment of CLO (15 mg/kg/day) markedly elevated serum lipid levels and resulted in hepatic lipid accumulation, whereas co-treatment of CUR (80 mg/kg/day) alleviated the CLO-induced dyslipidemia. We further demonstrated that CUR appears to be a novel AMP-activated protein kinase (AMPK) agonist, which enhanced AMPK phosphorylation and mitigated CLO-induced SREBP overexpression. Additionally, CUR also modulated the downstream SREBP-targeted genes involved in fatty acid synthesis and cholesterol metabolism, including fatty acid synthase (FAS) and HMG-CoA reductase (HMGCR). In summary, our study suggests that the suppressed AMPK activity and thereby enhanced SREBP-dependent lipid synthesis could be associated with the antipsychotic-stimulated dyslipidemia, whereas CUR may maintain lipid homeostasis by directly binding to AMPK, indicating that adjunctive use of CUR could be a promising preventive strategy for the drug-induced lipogenesis.