Effect of EGCG on inflammatory reaction in rats suffered cerebral ischemia/reperfusion injury

Epigallocatechin gallate (EGCG) is the main bioactive component of polyphenols in tea, which has a variety of biological effects. The neurologic injury caused by cerebral ischemia/reperfusion (I/R) is closely related to the inflammatory reaction. The pro-inflammatory factor interleukin-1β (IL-1β) and the anti-inflammatory factor interleukin-10 (IL-10) play important roles in the regulation of inflammatory reaction. This study aims to explore the effect of EGCG on water content, myeloperoxidase (MPO) activity, IL-1β and IL-10 in brain tissues of rats suffered cerebral I/R injury.

Middle cerebral artery occlusion model of SD rats was established by suture embolic method. After ischemia for 1.5 h, the nylon thread was pulled out and reperfusion was performed for 24.0 h. SD rats were randomly divided into 5 groups: a sham group, an I/R group, a EGCG1 group (I/R+12.5 mg/kg EGCG), a EGCG2 (I/R+25.0 mg/kg EGCG), and a EGCG3 group (I/R+50.0 mg/kg EGCG). The sham group was the same as the I/R group except that the middle cerebral artery was not blocked. The water content in brain tissues of rats was measured by dry and wet weight method, and MPO activity was detected by colorimetry. The levels of IL-1β and IL-10 mRNA were determined by RT-PCR, and the contents of IL-1β and IL-10 were determined by ELISA. In addition, primary cultured cortical neurons of SD rats were randomly divided into 3 groups: a control group, an oxygen-glucose deprivation/reperfusion (OGD/R) group, and an OGD/R+EGCG group (OGD/R+50.0 μmol/L EGCG). The effects of EGCG on the levels of IL-1β and IL-10 protein in neurons were assessed by Western blotting.

Compared with the sham group, water content, MPO activity, the contents of IL-1β and IL-10 were significantly increased (P<0.05 or P<0.01), the mRNA expression of IL-1β and IL-10 were obviously up-regulated (both P<0.01) in cerebral tissues of rats in the I/R group. Compared with the I/R group, water content and MPO activity in cerebral tissues of rats were significantly decreased (both P<0.01), the content of IL-1β (P<0.01) were significantly decreased and IL-10 (P<0.01) were significantly increased in the EGCG3 group. Compared with the I/R group, the mRNA expression of IL-1β was obviously down-regulated and the mRNA expression of IL-10 was obviously up-regulated in the EGCG2 and the EGCG3 group (P<0.05 or P<0.01). Compared with the control group, the protein levels of IL-1β and IL-10 in neurons were significantly increased in the OGD/R group (both P<0.01). Compared with the OGD/R group, the protein expression of IL-1β was obviously down-regulated and the protein expression of IL-10 was obviously up-regulated in neurons in the OGD/R+EGCG group (both P<0.01).

EGCG can inhibit the inflammatory reaction induced by cerebral I/R, which may be related to down-regulating the expression of pro-inflammatory factor IL-1β and up-regulating anti-inflammatory factor IL-10.