Isorhamnetin attenuates Streptococcus suis virulence by inhibiting the inflammatory response.

Streptococcus suis (S. suis) is one of the most common swine pathogens in the swine industry and leads to great harm to the normal progress of the swine industry. S. suis can also infect humans and cause a variety of fatal diseases, such as meningitis and streptococcal toxic shock syndrome, that pose a major threat to the safety of life and health of both humans and animals. In this paper, we found that isorhamnetin, a natural flavonoid compound without activity against S. suis, could significantly reduce the S. suis-stimulated production of the inflammatory cytokines interleukin (IL)-1β, IL-6, and tumor necrosis factor alpha (TNF-α) and down-regulate the inflammatory response by inhibiting the activation of p38 and ERK in tissues infected with S. suis, thereby exerting protection against S. suis infection. The above findings suggest that isorhamnetin is a potential lead compound for the treatment of S. suis infections, thus laying a preliminary theoretical foundation for the further development of isorhamnetin as a candidate drug.