Inactivation of mouse transmembrane prolyl 4-hydroxylase increases blood brain barrier permeability and ischemia-induced cerebral neuroinflammation.

Hypoxia-inducible factor prolyl 4-hydroxylases (HIF-P4Hs) regulate the hypoxic induction of >300 genes required for survival and adaptation under oxygen deprivation. Inhibition of HIF-P4H-2 has been shown to be protective in focal cerebral ischemia rodent models, while that of HIF-P4H-1 has no effects and inactivation of HIF-P4H-3 has adverse effects. A transmembrane prolyl 4-hydroxylase (P4H-TM) is highly expressed in the brain and contributes to the regulation of HIF, but the outcome of its inhibition on stroke is yet unknown. To study this, we subjected WT and P4htm-/- mice to permanent middle cerebral artery occlusion (pMCAO). Lack of P4H-TM had no effect on lesion size following pMCAO, but increased inflammatory microgliosis and neutrophil infiltration was observed in the P4htm-/- cortex. Furthermore, both the permeability of blood brain barrier and ultrastructure of cerebral tight junctions were compromised in P4htm-/- mice. At the molecular level, P4H-TM deficiency led to increased expression of proinflammatory genes and robust activation of protein kinases in the cortex, while expression of tight junction proteins and the neuroprotective growth factors erythropoietin and vascular endothelial growth factor was reduced. Our data provide the first evidence that P4H-TM inactivation has no protective effect on infarct size and increases inflammatory microgliosis and neutrophil infiltration in the cortex at early stage after pMCAO. When considering HIF-P4H inhibitors as potential therapeutics in stroke, the current data support that isoenzyme-selective inhibitors that do not target P4H-TM or HIF-P4H-3 would be preferred.

Myocardial infarction coincides with increased NOX2 and Nε-(carboxymethyl) lysine expression in the cerebral microvasculature.

BACKGROUND: Myocardial infarction (MI) is associated with mental health disorders, in which neuroinflammation and cerebral microvascular dysfunction may play a role. Previously, we have shown that the proinflammatory factors Nε-(carboxymethyl)lysine (CML) and NADPH oxidase 2 (NOX2) are increased in the human infarcted heart microvasculature. The aim of this study was to analyse the presence of CML and NOX2 in the cerebral microvasculature of patients with MI. METHODS: Brain tissue was obtained at autopsy from 24 patients with MI and nine control patients. According to their infarct age, patients with MI were divided into three groups: 3-6 hours old (phase I), 6 hours-5 days old (phase II) and 5-14 days old (phase III). CML and NOX2 in the microvasculature were studied through immunohistochemical analysis. RESULTS: We observed a 2.5-fold increase in cerebral microvascular CML in patients with phase II and phase III MI (phase II: 21.39±7.91, p=0.004; phase III: 24.21±10.37, p=0.0007) compared with non-MI controls (8.55±2.98). NOX2 was increased in microvessels in patients with phase II MI (p=0.002) and phase III MI (p=0.04) compared with controls. No correlation was found between CML and NOX2 (r=0.58, p=0.13). CONCLUSIONS: MI coincides with an increased presence of CML and NOX2 in the brain microvasculature. These data point to proinflammatory alterations in the brain microvasculature that may underlie MI-associated mental health disorders.

Bavachin exerted anti-neuroinflammatory effects by regulation of A20 ubiquitin-editing complex.

Neuroinflammation is a major pathophysiological contributor to the progression of the central nervous system disorders. Bavachin is a natural product belonging to the flavonoid class. The anti-neuroinflammatory effect and the molecular mechanisms are not well understood. In this study, we found bavachin can exert anti-neuroinflammatory effect via inhibition of nuclear factor-kappa B (NF-κB) signaling. We found that bavachin can obviously upregulate the expression of A20 (TNFAIP3) in microglial cells. Further studies suggested siRNA-A20 knockdown treatment can attenuate the inhibitory effects of bavachin on neuroinflammation. We further found bavachin can increase the interaction of ubiquitin-editing enzyme A20 complex including A20, Tax1-binding protein 1 (TAX1BP1) and Itch, the subsequently downregulated the K63-ubiquitination of TNF receptor associated factor 6 (TRAF6) and NF-κB signaling pathway. Altogether, our results indicated that bavachin exerted anti-neuroinflammatory effects through inhibition of NF-κB signaling mediated by regulation of ubiquitin-editing enzyme A20 complex. Our finding has important clinical significance for the potential application of bavachin in the treatment of neurological disorders.

Tadalafil and bergapten mitigate streptozotocin-induced sporadic Alzheimer's disease in mice via modulating neuroinflammation, PI3K/Akt, Wnt/ß-catenin, AMPK/mTOR signaling pathways.

Sporadic Alzheimer's disease (SAD) is a slowly progressive neurodegenerative disorder. This study aimed to investigate neuroprotective potential of tadalafil (TAD) and bergapten (BG) in SAD-induced cognitive impairment in mice. SAD was induced by single injection of streptozotocin (STZ; 3 mg/kg, ICV). STZ resulted in AD-like pathologies including Aß deposition, tau aggregation, impaired insulin and Wnt/ß-catenin signaling, as well as autophagic dysfunction and neuroinflammation. Administration of TAD or BG at doses of 20 and 25 mg/kg, respectively, for 21 consecutive days attenuated STZ-induced hippocampal insult, preserved neuronal integrity, and improved cognitive function in the Morris water maze and object recognition tests paralleled by reduction in Aß expression by 79 and 89% and tau hyperphosphorylation by 60 and 61%, respectively. TAD and BG also enhanced protein expression of pAkt, pGSK-3ß, beclin-1 and methylated protein phosphatase 2A (PP2A) and gene expression of cyclin D1, while raised BDNF immunoreactivity. Furthermore, TAD and BG boosted hippocampal levels of cGMP, PKG, Wnt3a, and AMPK and reduced expression of ß-catenin and mTOR by 74% and 51%, respectively. TAD and BG also halted neuroinflammation by reducing IL-23 and IL-27 levels, as well as protein expression of NF-κB by 62% & 61%, respectively. In conclusion, this study offers novel insights on the neuroprotective effects of TAD or BG in the management of SAD as evidenced by improved cognitive function and histological architecture. This could be attributed to modulation of the crosstalk among PI3K/Akt/GSK-3ß, PP2A, mTOR/autophagy, cGMP/PKG, and Wnt/ß-catenin signaling cascades and mitigation of neuroinflammation.