Molecular Factors in PAD2 (PADI2) and PAD4 (PADI4) Are Associated with Interstitial Lung Disease Susceptibility in Rheumatoid Arthritis Patients

Updates on interstitial lung disease and other selected extra-articular manifestations of rheumatoid arthritis

PURPOSE OF REVIEW

To discuss changes in epidemiology, recent advances in understanding of the pathogenesis and management of selected extraarticular manifestations of rheumatoid arthritis (ExRA).

RECENT FINDINGS

The incidence of ExRA overall and subcutaneous rheumatoid nodules in particular is declining after 2000. These trends reflect improved RA disease activity with early effective immunosuppressive treatments; changing environmental risk factors can be contributing. ExRA continues to carry a two-fold increased mortality risk. RA-associated interstitial lung disease (RA-ILD) is a major contributor to mortality, with no decline in incidence and scant therapeutic options. Individualized risk stratification for RA-ILD based on patient-level risk factors and biomarker profile is evolving with MUC5B as a major genetic risk factor. Clinical trials are underway to evaluate the benefits of novel antifibrotic therapies and targeted therapies for RA-ILD. The risk of cardiovascular disease in RA is generally amendable to treatment with disease-modifying antirheumatic drugs, although cardiovascular risk associated with JAK inhibition is not fully understood.

SUMMARY

Despite reduction in incidence of ExRA overall, the incidence of RA-ILD shows no significant decline and remains a major therapeutic challenge. The use of novel antifibrotics and immunosuppressive drugs shows promise in slowing the progression of RA-ILD.

Peptidyl Arginine Deiminases in Chronic Diseases: A Focus on Rheumatoid Arthritis and Interstitial Lung Disease

Protein citrullination is accomplished by a broad enzyme family named Peptidyl Arginine Deiminases (PADs), which makes this post-translational modification in many proteins that perform physiological and pathologic mechanisms in the body. Due to these modifications, citrullination has become a significant topic in the study of pathological processes. It has been related to some chronic and autoimmune diseases, including rheumatoid arthritis (RA), interstitial lung diseases (ILD), multiple sclerosis (MS), and certain types of cancer, among others. Antibody production against different targets, including filaggrin, vimentin, and collagen, results in an immune response if they are citrullinated, which triggers a continuous inflammatory process characteristic of autoimmune and certain chronic diseases. PAD coding genes (PADI1 to PADI4 and PADI6) harbor variations that can be important in these enzymes' folding, activity, function, and half-life. However, few studies have considered these genetic factors in the context of chronic diseases. Exploring PAD pathways and their role in autoimmune and chronic diseases is a major topic in developing new pharmacological targets and valuable biomarkers to improve diagnosis and prevention. The present review addresses and highlights genetic, molecular, biochemical, and physiopathological factors where PAD enzymes perform a major role in autoimmune and chronic diseases.