3.5 Koumine inhibits DNP-induced BLA astrocyte activation and ameliorates the inflammatory response
Given the role of BLA astrocytes in the development of pain hypersensitivity, we sought to examine whether the observed anti-allodynic effects of KM in the diabetic rats could occur by inhibiting the activation of BLA astrocytes. Immunofluorescence staining of the BLA showed that there was an increase proliferation and hypertrophy of astrocytes in the BLA, indicating that the activation of astrocytes was evidently increased in the DNP rats; however, treatment with KM (0.28, 1.4, and 7.0 mg/kg) attenuated the upregulation of GFAP in the diabetic rats (Fig. 6A-6C).
A dramatic increase in inflammatory cytokine levels is one of the major features of astroglial activation. Previous studies have reported that the release of inflammatory cytokines from active astrocytes is the primary cause of DNP (Ji et al., 2014). We examined the expression of proinflammatory cytokines in BLA tissue to investigate whether KM affected the inflammatory response caused by BLA astrocyte activation. ELISA results showed that TNF-α, IL-1β, CXCL1 and MCP-1 levels were markedly increased in the BLA of the DNP rats compared to those in the BLA of the control rats; however, this upregulation was reversed by KM (Fig. 7A-7D). Taken together, these results suggested that KM substantially inhibited DNP-induced BLA astrocyte activation and suppressed the astrocyte activation-induced inflammatory response.