Histamine H3R antagonist counteracts the impaired hippocampal neurogenesis in Lipopolysaccharide-induced neuroinflammation.

Adult neurogenesis in hippocampus dentate gyrus (DG) is associated with numerous neurodegenerative diseases such as aging and Alzheimer's disease (AD). Overactivation of microglia induced neuroinflammation is well acknowledged to contribute to the impaired neurogenesis in pathologies of these diseases and then leading to cognitive dysfunction. Histamine H3 receptor (H3R) is a presynaptic autoreceptor regulating histamine release via negative feedback way. Recently, studies show that H3R are highly expressed not only in neurons but also in microglia to modulate inflammatory response. However, whether inhibition of H3R is responsible for the neurogenesis and cognition in chronic neuroinflammation induced injury and the mechanism remains unclear. In this study, we found that inhibition of H3R by thioperamide reduced the microglia activity and promoted a phenotypical switch from pro-inflammatory M1 to anti-inflammatory M2 in microglia, and ultimately attenuated lipopolysaccharide (LPS) induced neuroinflammation in mice. Additionally, thioperamide rescued the neuroinflammation induced impairments of neurogenesis and cognitive function. Mechanically, the neuroprotection of thioperamide was involved in histamine dependent H2 receptor (H2R) activation, because cimetidine, an H2R antagonist but not pyrilamine, an H1R antagonist reversed the above effects of thioperamide. Moreover, thioperamide activated the H2R downstream phosphorylated protein kinase A (PKA)/cyclic AMP response element-binding protein (CREB) pathway but inhibited nuclear factor kappa-B (NF-κB) signaling. Activation of CREB by thioperamide promoted interaction of CREB-CREB Binding Protein (CBP) to increase anti-inflammatory cytokines (Interleukin-4 and Interleukin-10) and brain-derived neurotrophic factor (BDNF) release but inhibited NF-κB-CBP interaction to decrease pro-inflammatory cytokines (Interleukin-1ß, Interleukin-6 and Tumor necrosis factor α) release. H89, an inhibitor of PKA/CREB signaling, abolished effects of thioperamide on neuroinflammation and neurogenesis. Taken together, these results suggested under LPS induced neuroinflammation, the H3R antagonist thioperamide inhibited microglia activity and inflammatory response, and ameliorated impairment of neurogenesis and cognitive dysfunction via enhancing histamine release. Histamine activated H2R and reinforced CREB-CBP interaction but weakened NF-κB-CBP interaction to exert anti-inflammatory effects. This study uncovered a novel histamine dependent mechanism behind the therapeutic effect of thioperamide on neuroinflammation.

Thioperamide attenuates neuroinflammation and cognitive impairments in Alzheimer's disease via inhibiting gliosis.

Alzheimer's disease (AD) is an age-related neurodegenerative disease, which characterized by deposition of amyloid-ß (Aß) plaques, neurofibrillary tangles, neuronal loss, and accompanied by neuroinflammation. Neuroinflammatory processes are well acknowledged to contribute to the progression of AD pathology. Histamine H3 receptor (H3R) is a presynaptic autoreceptor regulating histamine release via negative feedback way. Recently, studies show that H3R are highly expressed not only in neurons but also in microglia and astrocytes. H3R antagonist has been reported to have anti-inflammatory efficacy. However, whether inhibition of H3R is responsible for the anti-neuroinflammation in glial cells and neuroprotection on APPswe, PSEN1dE9 (APP/PS1 Tg) mice remain unclear. In this study, we found that inhibition of H3R by thioperamide reduced the gliosis and induced a phenotypical switch from A1 to A2 in astrocytes, and ultimately attenuated neuroinflammation in APP/PS1 Tg mice. Additionally, thioperamide rescued the decrease of cyclic AMP response element-binding protein (CREB) phosphorylation and suppressed the phosphorylated P65 nuclear factor kappa B (p-P65 NF-κB) in APP/PS1 Tg mice. H89, an inhibitor of CREB signaling, abolished these effects of thioperamide to suppress gliosis and proinflammatory cytokine release. Lastly, thioperamide alleviated the deposition of amyloid-ß (Aß) and cognitive dysfunction in APP/PS1 mice, which were both reversed by administration of H89. Taken together, these results suggested the H3R antagonist thioperamide improved cognitive impairment in APP/PS1 Tg mice via modulation of the CREB-mediated gliosis and inflammation inhibiting, which contributed to Aß clearance. This study uncovered a novel mechanism involving inflammatory regulating behind the therapeutic effect of thioperamide in AD.

l-carnitine protects human hepatocytes from oxidative stress-induced toxicity through Akt-mediated activation of Nrf2 signaling pathway.

In our previous study, l-carnitine was shown to have cytoprotective effect against hydrogen peroxide (H2O2)-induced injury in human normal HL7702 hepatocytes. The aim of this study was to investigate whether the protective effect of l-carnitine was associated with the nuclear factor erythroid 2 (NFE2)-related factor 2 (Nrf2) pathway. Our results showed that pretreatment with l-carnitine augmented Nrf2 nuclear translocation, DNA binding activity and heme oxygenase-1 (HO-1) expression in H2O2-treated HL7702 cells, although l-carnitine treatment alone had no effect on them. Analysis using Nrf2 siRNA demonstrated that Nrf2 activation was involved in l-carnitine-induced HO-1 expression. In addition, l-carnitine-mediated protection against H2O2 toxicity was abrogated by Nrf2 siRNA, indicating the important role of Nrf2 in l-carnitine-induced cytoprotection. Further experiments revealed that l-carnitine pretreatment enhanced the phosphorylation of Akt in H2O2-treated cells. Blocking Akt pathway with inhibitor partly abrogated the protective effect of l-carnitine. Moreover, our finding demonstrated that the induction of Nrf2 translocation and HO-1 expression by l-carnitine directly correlated with the Akt pathway because Akt inhibitor showed inhibitory effects on the Nrf2 translocation and HO-1 expression. Altogether, these results demonstrate that l-carnitine protects HL7702 cells against H2O2-induced cell damage through Akt-mediated activation of Nrf2 signaling pathway.

[Effect of panax notoginseng powder on pathological features and expressions of VEGF and its receptors of chronic subdural hematoma rabbits: an experimental study].

OBJECTIVE: To observe the effect of Panax notoginseng (PN) on pathological features in chronic subdural hematoma (CSDH) rabbits and its mechanisms. METHODS: A stable pathological animal model similar to CSDH in humans could be established using subdural injections of small number of blood through a subdural pre-catheter in rabbits. After successful modeling, 18 rabbits were randomly divided into the model group, the low dose PN group (0.125 g/kg), and the high dose PN group (0.250 g/kg), 6 in each group. Normal saline was given to rabbits in the model group, while PN power was given to those in the PN groups by gastrogavage for 6 successive days. Pathologic features of the hematoma outer membrane were observed by HE staining. The activity of SOD and the content of MDA in the hematoma outer membrane were examined by the colorimetric method. Expressions of CD31, CD34, and VEGF in the hematoma outer membrane were observed by immunohistochemical assay. Expressions of VEGF in the peripheral blood and the subdural hematoma were detected by enzyme-linked immunosorbent assay (ELISA). Expressions of VEGFR-1 and VEGFR-2 in the hematoma outer membrane were detected by Western blot. RESULTS: Compared with the model group, the inflammatory reaction was comparatively lessen and the proliferation of the fibrous tissue was relatively mature in the low and high dose PN groups. The activity of SOD increased (P < 0.05); expressions of CD31 and CD34 were reduced (P < 0.01); VEGF expression in the residual hematoma fluid decreased (P < 0.05) in the high dose PN group. Expressions of VEGF and VEGFR-2 were all reduced in the high and low dose PN groups (P < 0. 05, P < 0.01). Compared with the low dose PN group, expressions of CD31 and CD34 were reduced (P < 0.01), and the VEGFR-2 expression was also reduced (P < 0.05) in the high dose PN group. CONCLUSIONS: PN could promote the fibrous repairing of subdural hematoma in CSDH rabbits. It also lessened inflammation and oxidative injury of the hematoma outer membrane and reduced expressions of VEGF. The pathological angiogenesis could be reduced through influencing VEGFR-2 receptor pathways, which might be an important mechanism.

Cornin induces angiogenesis through PI3K-Akt-eNOS-VEGF signaling pathway.

In the present study, we sought to elucidate whether Cornin contributes to induce angiogenesis and its mechanisms. To this end, we examined the role of Cornin on human brain microvascular endothelial cell line (HBMEC) proliferation, invasion, and tube formation in in vitro. For study of mechanism, the phosphoinositide 3 kinase (PI3K)-Akt inhibitor LY294002, endothelial nitric oxide synthase (eNOS) inhibitor L-NAME, vascular endothelial growth factor (VEGF) antagonist sFlt-1 and VEGF receptor blocker SU-1498 were used. HMBEC proliferation was tested by MTT. Scratch adhesion test was used to assess the ability of invasion. A matrigel tube formation assay was performed to test capillary tube formation ability. PI3K-Akt-eNOS-VEGF pathway activation in HMBEC was tested by Western blot. Our data suggested that Cornin induces angiogenesis in vitro by increasing proliferation, invasion and tube formation. VEGF expression was increasing by Cornin and counteracted by VEGF antagonist sFlt-1, LY294002 and L-NAME in HMBEC. Tube formation was increased by Cornin and counteracted by VEGF receptor blocker-SU1498, LY294002 and L-NAME. It may be suggested that Cornin induces angiogenesis in vitro via a programmed PI3K/Akt/eNOS/VEGF signaling axis.

Rosmarinic acid protects against experimental diabetes with cerebral ischemia: relation to inflammation response.

BACKGROUND: Inflammatory activation plays a vital role in the pathophysiological mechanisms of stroke, exerting deleterious effects on the progression of tissue damage and may lead to the vascular damage in diabetes. The objectives of this study were to determine the effects of rosmarinic acid (RA) on a cultured neuronal cell line, SH-SY5Y in vitro and experimental ischemic diabetic stroke in vivo. METHODS: For oxygen-glucose deprivation (OGD) and tumor necrosis factor-α (TNF-α) stimulated SH-SY5Y cell line in vitro, SH-SY5Y cells were incubated with RA. For an in vivo experiment, diabetic rats were subjected to middle cerebral artery occlusion (MACO) for 40 minutes followed by reperfusion for 23 h. RESULTS: Treatment of SH-SY5Y cells with RA reduced the OGD-induced apoptosis and cytotoxicity, blocked TNF-α-induced nuclear transcription factor κB (NF-κB) activation, and decreased high-mobility group box1 (HMGB1) expression. At doses higher than 50 mg/kg, RA produced a significant neuroprotective potential in rats with ischemia and reperfusion (I/R). RA (50 mg/kg) demonstrated significant neuroprotective activity even after delayed administration at 1 h, 3 h and 5 h after I/R. RA 50 mg/kg attenuated histopathological damage, decreased brain edema, inhibited NF-κB activation and reduced HMGB1 expression. CONCLUSION: These data show that RA protects the brain against I/R injury with a favorable therapeutic time-window by alleviating diabetic cerebral I/R injury and attenuating blood-brain barrier (BBB) breakdown, and its protective effects may involve HMGB1 and the NF-κB signaling pathway.