Salvianolic acid B (SalB), a natural polyphenolic compound extracted from the herb of Salvia miltiorrhiza, possesses antioxidant and neuroprotective properties and has been shown to be beneficial for diseases that affect vasculature and cognitive function. Here we investigated the protective effects of SalB against subarachnoid hemorrhage (SAH)-induced oxidative damage, and the involvement of underlying molecular mechanisms. In a rat model of SAH, SalB inhibited SAH-induced oxidative damage. The reduction in oxidative damage was associated with suppressed reactive oxygen species generation; decreased lipid peroxidation; and increased glutathione peroxidase, glutathione, and superoxide dismutase activities. Concomitant with the suppressed oxidative stress, SalB significantly reduced neurologic impairment, brain edema, and neural cell apoptosis after SAH. Moreover, SalB dramatically induced nuclear factor-erythroid 2-related factor 2 (Nrf2) nuclear translocation and increased expression of heme oxygenase-1 and NADPH: quinine oxidoreductase-1. In a mouse model of SAH, Nrf2 knockout significantly reversed the antioxidant effects of SalB against SAH. Additionally, SalB activated sirtuin 1 (SIRT1) expression, whereas SIRT1-specific inhibitor sirtinol pretreatment significantly suppressed SalB-induced SIRT1 activation and Nrf2 expression. Sirtinol pretreatment also reversed the antioxidant and neuroprotective effects of SalB. In primary cultured cortical neurons, SalB suppressed oxidative damage, alleviated neuronal degeneration, and improved cell viability. These beneficial effects were associated with activation of the SIRT1 and Nrf2 signaling pathway and were reversed by sirtinol treatment. Taken together, these in vivo and in vitro findings suggest that SalB provides protection against SAH-triggered oxidative damage by upregulating the Nrf2 antioxidant signaling pathway, which may be modulated by SIRT1 activation.

Previous studies have demonstrated resveratrol (RSV) has beneficial effects in early brain injury (EBI) after subarachnoid hemorrhage (SAH). However, the beneficial effects of RSV and the underlying mechanisms have not been clearly identified. The nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome activation plays a crucial role in the EBI pathogenesis. The aim of this study was to investigate the role of RSV on the NLRP3 inflammasome signaling pathway and EBI in rats after SAH. A prechiasmatic cistern injection model was established in rats, and the primary cultured cortical neurons were stimulated with oxyhemoglobin (oxyHb) to induce SAH in vitro. It showed that the NLRP3 inflammasome components, including NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), caspase-1, mature interleukin-1β (IL-1β), and interleukin-18 (IL-18) were upregulated after SAH, and the enhanced NLRP3 after SAH was mainly located in microglia. Treatment with 60 or 90 mg/kg RSV after SAH dramatically inhibited the expression of NLRP3, but there was no significant difference in the expression of NLRP3 between the SAH + 60 mg/kg RSV and SAH + 90 mg/kg RSV groups. In addition, treatment with 30 mg/kg RSV did not significantly reduced the expression of NLRP3. We next evaluated the neuroprotective effects of RSV against SAH. We determined that SAH-induced NLRP3 inflammasome activation was significantly inhibited in the SAH + 60 mg/kg RSV group. Meanwhile, 60 mg/kg RSV administration could markedly inhibit microglia activation and neutrophils infiltration after SAH. Concomitant with the decreased cerebral inflammation, RSV evidently reduced cortical apoptosis, brain edema, and neurobehavioral impairment after SAH. In vitro experiments, RSV treatment also clearly protected primary cortical neurons against oxyHb insults, including reduced the proportion of neuronal apoptosis, alleviated neuronal degeneration, and improved cell viabilities. These in vitro data further confirm that RSV has an efficient neuroprotection against SAH. Taken together, these in vivo and in vitro findings suggested RSV could protect against EBI after SAH, at least partially via inhibiting NLRP3 inflammasome signaling pathway.

Inflammation plays a key role in the progression of subarachnoid hemorrhage (SAH). Here, we examined the effects of astaxanthin (ATX) on the inflammatory response and secondary damage after SAH and the underlying mechanisms of action. In vivo, a prechiasmatic cistern injection model was established in rats and mice. In addition, neuron-microglia cocultures were exposed to oxyhemoglobin to mimic SAH in vitro. Western blotting revealed that protein expression of TLR4 was markedly increased in microglia at 24 h after SAH, with consequent increases in the downstream molecules myeloid differentiation factor 88 and NF-кB. Treatment with ATX significantly inhibited the TLR4 activation, increased sirtuin 1 expression, and inhibited the subsequent inflammatory response both in vivo and in vitro. ATX also significantly decreased high-mobility group box 1 nuclear translocation and secretion in neurons, an effect that was reversed by the sirtuin 1-specific inhibitor sirtinol. ATX administered 4 h after SAH ameliorated cerebral inflammation, brain edema, and neuronal death and improved neurologic function. ATX reduced neuronal death but did not improve neurologic function in TLR4 knockout mice. These results suggest that ATX reduces the proinflammatory response and secondary brain injury after SAH, primarily by increasing sirtuin 1 levels and inhibiting the TLR4 signaling pathway.-Zhang, X., Lu, Y., Wu, Q., Dai, H., Li, W., Lv, S., Zhou, X., Zhang, X., Hang, C., Wang, J. Astaxanthin mitigates subarachnoid hemorrhage injury primarily by increasing sirtuin 1 and inhibiting the Toll-like receptor 4 signaling pathway.