The outbreak of coronavirus disease 2019 (COVID-19), caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection, has emerged in China in December 2019 and rapidly spread to more than 196 countries worldwide. The physiopathology of human SARS-CoV-2 has not been completely understood, but its pathogenesis has been linked to a disproportionate response of the immune system. Just as described for SARS and MERS, an uncontrolled systemic inflammatory response, known as cytokine release syndrome (CRS) was observed in severe COVID-19 patients. It results from the release by immune and non-immune effector cells of substantial amounts of pro-inflammatory cytokines and appears to contribute to SARS-CoV-2 pulmonary inflammation and extensive lung damage. In addition, hyper-coagulation and thrombosis resulted from the important release of pro-inflammatory cytokines contribute to the lethality of subjects severely infected with SARS-CoV-2. It is therefore essential to have a deep understanding of the various cytokines involved in this exacerbated immune response, and that could be targeted by potential immunological treatments. The aim of this review was to gather the current knowledge about the role of pro-inflammatory cytokines, namely IL-1β, IL-6, IL-8, IL-17 and TNFα in SARS-CoV-2 CRS , the probable causes and clinical outcomes of this phenomenon in severe cases of COVID-19.

Leishmania major is a protozoan parasite from one of the most ancient phylogenic branches of unicellular eukaryotes, and containing only one giant mitochondrion. Here we report that staurosporine, that induces apoptosis in all mammalian nucleated cells, also induces in L. major a death process with several cytoplasmic and nuclear features of apoptosis, including cell shrinkage, phosphatidyl serine exposure, maintenance of plasma membrane integrity, mitochondrial transmembrane potential (DCm) loss and cytochrome c release, nuclear chromatin condensation and fragmentation, and DNA degradation. Nuclear apoptosis-like features were prevented by cysteine proteinase inhibitors, and cell free assays using dying L. major cytoplasmic extracts indicated that the cysteine proteinases involved (i) also induced nuclear apoptosis-like features in isolated mammalian nuclei, and (ii) shared at least two nuclear substrates, but no cleavage site preference, with human effector caspases. Finally, isolated L. major mitochondria released cytochrome c and cysteine proteinases with nuclear pro-apoptotic activity when incubated with human recombinant Bax, even (although much less efficiently) when Bax was deleted of its transmembrane domain required for insertion in mitochondrial outermembranes, implying that L. major mitochondrion may express proteins able to interact with Bax. The recruitment of cysteine proteinases and mitochondria to the cell death machinery may be of very ancient evolutionary origin. Alternately, host/ parasite interactions may have exerted selective pressures on the cell death phenotype of kinetoplastid parasites, resulting in the more recent emergence of an apoptotic machinery through a process of convergent evolution.