Abstract
SARS-CoV-2 viral-derived particles have been proposed to have a causal role in tissue inflammation. Macrophage is the culprit cell in the pathogenesis of destructive inflammatory response to the SARS-CoV-2 virus. We investigated whether the spike protein might play a role in perturbing the physiological process of resolution of inflammation. Using an in vitro model of M2 polarized macrophages, we found that recombinant spike protein produced typical M1 morphological features in these alternative differentiated cells. In the presence of spike, M2-macrophages lose their elongated morphology, become rounded and acquire a strong capability to stimulate lymphocyte activation and proliferation. Moreover, in M2 macrophages, spike activated the signal transducer and activator-1 (STAT1) the pivotal mediator of pro-inflammatory macrophages. We observed STAT1 activation also in endothelial cells cultured with recombinant spike, accompanied by Bax upregulation and cell death. Blockade of beta3 integrin with the RGD mimetic tirofiban reverted the spike-induced costimulatory effects on M2 macrophages. Also, tirofiban counteracted STAT1 and Bax activation in endothelial cells cultured with spike and reduced endothelial cell death. In conclusion, we found that some proinflammatory effects of the spike protein can involve the integrin pathway and provide elements supporting use of RGD mimetics against SARS-Cov-2.