The Critical Role of IL-10 in the Antineuroinflammatory and Antioxidative Effects of Rheum tanguticum on Activated Microglia

Abstract EN

Rheum tanguticum Maxim.

ex Balf.

(Rt), a traditional Tibetan medicine, is known to exert various bioactivities, including anti-inflammatory and antioxidative activities.

The present study was conducted to investigate anti-inflammatory and antioxidative effects of Rt on activated microglia.

Rt (10 μg/ml) significantly inhibited the mean protein level of interleukin-1β (IL-1β) in the organotypic hippocampal slice cultures following treatment with chromogranin A (CGA, 10 nM) and pancreastatin (10 nM), endogenous microglial activators present in senile plaques.

Rt also significantly inhibited the expression and production of inflammatory and oxidative molecules, including IL-1β, tumor necrosis factor-α, and nitric oxide, by cultured microglia after treatment with CGA.

These effects of Rt are considered to be mediated by the secretion of interleukin-10 (IL-10) from microglia, because neutralizing antibodies against IL-10 significantly canceled these effects.

To explore the causative components of Rt responsible for inducing the secretion of IL-10, the effects of seven components of Rt on the IL-10 expression in microglia were examined.

Among them, aloe-emodin (10 μM) and (+)-catechin (30 μM) were able to induce the secretion of IL-10 from cultured microglia.

Therefore, aloe-emodin and (+)-catechin are deemed responsible for the antineuroinflammatory and antioxidative effects of Rt through the secretion of IL-10 from microglia.

Accordingly, Rt is considered potentially useful for the treatment of AD.