Suppressive effects of sunitinib on a TLR activation-induced cytokine storm

The cytokine storm includes a clinically heterogeneous set of life-threatening conditions that are manifested by extremely elevated serum cytokine levels and related symptoms (e.g., septic shock) and is devilishly mediated by Toll-like receptor (TLR) agonists in most situations. A tyrosine kinase inhibitor (TKIs), sunitinib, was screened in our group previously and showed antagonistic activity for cytokine release in a TLR7 stimulation model. In this paper, we further studied its mechanisms on interesting phenomena. In vitro, nearly all of the eleven TKIs decreased the TNF-α levels induced by the TLR7 agonist, especially sunitinib. Furthermore, sunitinib displayed potent inhibition of the cytokine levels triggered by several types of TLR ligands, including TLR3, TLR4, TLR7/8 and TLR9, in mouse spleen lymphocytes, mouse BMDCs and human PBMCs. The in vivo results showed that sunitinib efficiently depressed the LPS-induced cytokine storm, i.e., rapid and intense production of TNF-α and IL-6. Sunitinib further increased the survival time and decreased damage to mice. As for the immunosuppressive mechanisms of sunitinib, at least the PDGFR-activated ERK and p38 pathways were critical, although we could not rule out the possibility of other pathways being involved. In conclusion, our study demonstrated the inhibitory actions of TKIs on the cytokine storm induced by TLR ligands, primarily through PDGFR pathways, which could be potentially used to reduce cytokine storms in septic shock.