Ranitidine as adjuvant regulates macrophage polarization and activates CTL through PI3K-Akt2 signal pathway

Abstract Adjuvant is an indispensable component of vaccines, but there are few adjuvants for human vaccines. It has been found that H2 receptor blockers, inhibiting gastric acid secretion, had immune enhancement effect. Ranitidine (RAN) is a water-soluble H2 receptor blocker, whether it has immune enhancing effect is still unknown. In this study, flow cytometry, western blot, immunofluorescence methods were used to analyzed whether RAN could activate macrophages polarization to M1 in vivo and vitro. Here, we found that the M1 inflammatory cytokine levels and surface markers in RAW264.7 cells were up-regulated by NF-κB activation possibly through PI3K-Akt2 signal pathway after RAN treated. Meanwhile, endocytosis function also been enhanced by feedback regulation of Akt2/GSK3β/Dynmin1 signal. Furtherly, to evaluate the adjuvant function of RAN, we used OVA plus RAN as a vaccine to inhibit the growth of B16-OVA tumors in mice. We also found that in the RAN adjuvant group, macrophage polarization to M1, Th1 cell differentiation, and cytotoxic T lymphocytes (CTL) activation were significantly up-regulated. The tumor growth of mice was inhibited, and the survival rate of mice was significantly improved. This study provided new evidence for the mechanism of RAN activating immune responding, and was expected to provide a new strategy for the research and development of tumor vaccine adjuvant.