Mandar Dave1,2, Abul BMMK Islam3 and Ashok R Amin1,4,5*
1Department of Bio-Medical Engineering, Virginia Tech, Blacksburg, Virginia, USA
2Department of Science, STEM Division, Union County College, Cranford, New Jersey, USA
3Department of Genetic Engineering and Biotechnology, University of Dhaka, Dhaka, Bangladesh
4Department of Rheumatology, New York University-Hospital for Joint Diseases, NY 10003, USA
5RheuMatric Inc., Blacksburg, Virginia, USA
The effects of up regulated high mobility group box-1 (HMGB1) and nitric oxide (NO) contributes to pro-inflammatory activity in the synovial tissue and matrix depleting activity in human osteoarthritis (OA)-affected cartilage. The 215-amino acid HMGB1 protein has several functional domains with multiple over lapping functions. Since HMGB1 can induce NO production in cartilage, we tested the requirements of different functional areas of HMGB1 that can modulate NO in human OA-affected cartilage in ex vivo conditions. Recombinant HMGB1 proteins and various deletions mutants of HMGB1 were generated and purified. Human OA-affected cartilage that spontaneously released NO in ex vivo conditions was utilized as a model to test the effect of HMGB1 (and various HMGB1 mutants) to modulate the natural release of NO in ex vivo conditions. HMGB1 and deletion mutants of HMGB1 which retained the B-Box of HMGB1 had the ability to significantly augment the spontaneous release of NO in OA-affected cartilage in 24 h. Removal of the C-terminal acidic region of HMGB1 further significantly amplified NO production, whereas the A-Box of HMGB1 had no significant effect on NO-production. Furthermore, HMGB1+A-Box had no significant effect on the NO-augmenting activity of HMGB1. This paper for the first time shows that the B-Box of HMGB1 harbors the NO-augmenting activity and the C-terminal acidic tail functions as a negative regulator of HMGB1’s-NO-augmenting activity in human cartilage. Therapeutic intervention of the B-Box is a promising target to deter the detrimental effects of escalated levels and effects of both HMGB1 and NO in human OA-affected joints.
HMGB1; B-box; Nitric oxid; Cartilage; Arthritis
Dave M, Abul BMMK Islam, Ashok R Amin. The B-Box of HMGB1 Amplifies Nitric Oxide Production in Human Osteoarthritis-Affected Cartilage. Am J Arthritis. 2017;1(1):1002.