CCN2 and pulmonary fibrosis: Although there is no data so far about protein citrullination level in COVID patients suffering from lung fibrosis, it was found that in a model of lung fibrosis induced by cadmium and carbon black (Cd/CB), two cigarette components providing a model for cigarette smoke, the level of citrullinated vimentin (Cit-vim) was significantly increased and was related with a TLR4-dependent activation of NF-κB and the production of active TGF-β1, CTGF (Connective Tissue Growth Factor) and IL-8 [157].