Effects of hydroxytyrosol-20 on carrageenan-induced acute inflammation and hyperalgesia in rats

Hydroxytyrosol (HT) is a simple phenol compound extracted from olive leaves. The content of HT in the studied preparation was about 20%, and the preparation was called hydroxytyrosol-20 (HT-20). HT has antioxidant and antiinflammatory activities. There has been no report so far on the efficacy of HT-20 in carrageenan-induced acute inflammation and hyperalgesia in rats. Therefore, the aim of this study was to assess the inhibitory role of HT-20 on carrageenan-induced swelling and hyperalgesia of rat paw. Paw inflammation was assessed by the increase in paw volume and hyperalgesia. The rat paws were cut out under ether anesthesia at 270 min after administration of carrageenan. The tissue of the right paw was isolated separately from the individual rat. The levels of the tumor necrosis factor-alpha (TNF-alpha), interleukin 1beta (IL-1beta) and interleukin 10 (IL-10) mRNA in the tissue were estimated by reverse transcription-polymerase chain reaction (RT-PCR). The results showed that the paw pressure thresholds of rats orally administered HT-20 significantly increased at 210, 240 and 270 min after administration of carrageenan, compared with corresponding basal paw pressure thresholds; the degree of swelling of the right hind paw showed a statistically significant reduction, compared with rats in the carrageenan-treated control. In this model, HT-20 appears to decrease pro-inflammatory cytokines IL-1beta and TNF-alpha and not to increase the antiinflammatory cytokine mRNA expression of IL-10.