Chronic rejection remains a major barrier for the long-term survival of transplanted organs. After initial success, the majority of grafts will be lost in the years after a transplant as a recipient’s immune system slowly attacks and destroys the tissue. Leonardo Riella, MD, PhD, associate physician and assistant director of kidney transplantation at BWH, and his colleagues studied the impact of high salt intake on the immune response after transplantation and report evidence that high salt intake may accelerate transplant rejection. First author Kassem Safa, MD, of the Transplant Center and Division of Nephrology at Massachusetts General Hospital, and colleagues report their findings in the April 1 issue of The Journal of the American Society of Nephrology.
The research team first modeled the effects of higher salt concentration on T cells – a key component of the immune system – in the lab. Higher salt increased T cell proliferation. The team then used a pre-clinical transplant model to investigate the impact of salt on immune response by feeding a high- or normal-salt diet to mice that had received transplanted cardiac tissue. They observed accelerated rejection in the high-salt diet group along with disturbance in the balance of the immune system’s T cells, in particular, a deleterious effect of salt on regulatory T cells. The team also found that SGK1 – a signaling protein sensitive to salt in the body – was a key player leading to these effects.
“Although transplant recipients have a lower salt intake than the general population, their intake still exceeds the recommended amount in more than 80 percent of patients post-transplant,” said Riella, corresponding author of the study. “Given the endemic nature of salt consumption, additional investigation is warranted to assess potential benefits of salt-intake reduction in human transplantation.”