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Longxuetongluo capsule alleviates lipopolysaccharide-induced neuroinflammation by regulating multiple signaling pathways in BV2 microglia cells.

BACKGROUND
Longxuetongluo capsule (LTC), derived from the total phenolic compounds of Chinese dragon's blood, is now used in the treatment of ischemic stroke in convalescence. The aim of this study is to explore the neuroprotective effect of LTC from the perspective of neuroinflammation.


METHODS
Cell viability and lactate dehydrogenase (LDH) release were measured by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and LDH assay kit. Proinflammatory mediators and cytokines production including Nitric Oxide (NO), prostaglandin E2, (PGE2), interleukin (IL-β), IL-6, and tumor necrosis factor-α (TNF-α) were detected by enzyme-linked immunosorbent assay (ELISA) assay. In addition, western blot was used to detect the expression of inflammatory proteins associated with the mitogen-activated protein kinases (MAPKs), janus kinase/signal transducer and activator of tranions (JAK/STAT), nuclear transcription factor κB (NF-κB), and nuclear factor erythroid-2-related actor 2/heme oxygenase 1 (Nrf2/HO-1) signaling pathways. Moreover, immunofluorescence assay and electrophoretic mobility shift assays (EMSA) were performed to determine the Nrf2 translocation and the binding-DNA activity of NF-κB, respectively.


RESULTS
LTC at 0.5 to 2 μg/mL significantly increased cell viability and decreased LDH, NO, PGE2, IL-1β, IL-6, and TNF-α production in oxygen-glucose deprivation/reoxygenation (OGD/R) and lipopolysaccharide (LPS)-induced BV2 microglia cells. Meanwhile, LTC not only decreased the protein expressions of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) but also down-regulated phosphorylation of extracellular signal-regulated kinase (ERK)1/2, p38, and up-regulated HO-1 expression via nuclear translocation of Nrf2. LTC can significantly inhibit the phosphorylation of JAK1/STAT3 and reduce the translocation of NF-κB from cytosol to nucleus as well as the binding-DNA activity. PC12 cell pretreated with LTC-condition medium (CM) significantly alleviated LPS-induced neurotoxicity and increased PC12 cell viability in a dose-dependent manner.


CONCLUSION
The present study showed that LTC exhibited a strong antineuroinflammatory activity and neuroprotective effects on LPS-stimulated BV2 microglial cells and PC12 cells.