To characterize the activation state of inflammasome receptors NLRC4, involved in Salmonella spp. infection, and NLRP1, associated with endothelial damage, two frequent conditions in Sickle Cell Anaemia (SCA), in peripheral blood monocytes of SCA patients.

Blood samples were obtained from two HBB homozygotes SCA adult patients (in steady state) and three healthy blood donors (HD), according to the UNIFESP Ethical Committee approval. Peripheral blood monocytes were isolated by Ficoll gradient and plastic adherence and in vitro stimulated with known NLRC4 and NLRP1 activators, bacterial Flagellin and the dipeptidyl-peptidase-(DPP)-9 inhibitor, ValBoro-pro (Talabostat), respectively. Inflammasome activation was measured by IL-1ß release in culture supernatants. In some experiments, monocytes were pre-treated with the NF-kB and general inflammasome inhibitor Parthenolide and the Bruton Tyrosine Kinase (BTK) inhibitor CGI-1746. Cytokine release was compared between SCA and HD cells.

Flagellin and ValBoro-pro induced IL-1ß release in SCA and HD monocytes without significant differences between the two groups.

Here we showed that, at least in our in vitro model, NLRP1 and NLRC4 pathways are not significantly affected in SCA monocytes, reinforcing the idea that NLRP3 is the key contributor to inflammasome dysregulation and chronic inflammation in SCA, as we previously reported. Of note, differently from NLRP3, NLRP1 and NLRC4, are less expressed in monocytes, therefore suggesting that other types of leukocytes could be investigated for this purpose.

NLRP1 and NLRC4 pathways seem to not be affected in monocytes of SCA patients.