Atherosclerosis and osteoporosis: possible role of T cells.

L.S. Graham, F. Parhami, R.B. Effros
University of California, Los Angeles, Los Angeles, CA

Cardiovascular disease and osteoporosis are leading health care problems in our aging population. Numerous studies have documented an association between these two multifactorial and degenerative diseases. Moreover, atherosclerosis is considered to be a chronic inflammatory disease such that the immune system actually modulates the atherogenic process. In addition, the immune system plays a key role in bone resorption through production by activated T lymphocytes of RANKL (receptor activator for NFkB ligand), a protein that stimulates the maturation and activity of osteoclasts. Therefore, we sought to investigate the role of T lymphocytes in the decreased bone density associated with atherosclerosis.
Mice given an atherogenic diet had significantly higher total cholesterol and serum IL-6 levels compared to mice on normal diet. Furthermore, T cells isolated from the atherogenic group had significantly higher IL-6, IL-1b and RANKL expression levels than the normal fed mice. These cytokines are involved in inflammatory response and osteoclastogenesis. There were no difference in the proportion of mature T cells in the bone marrow; however, the atherogenic group had more activated memory T cells than their control counterpart. Our data suggests the possible involvement of T cells in bone loss associated with vascular disease.

Keywords: Atherosclerosis, Osteoporosis, T cells