Systemic lupus erythematosus (SLE) is an autoimmune inflammatory disease characterized by T-cell, B-cell, and dendritic cell dysfunction and
antinuclear autoantibody production. Much of the knowledge that has been gained about SLE in recent years is related to molecular signaling abnormalities present in the disease. Signaling through the
T-cell receptor (TCR) is affected in SLE by alterations in the localization, amount, and activity of numerous
protein kinases. TCR stimulation releases
calcium from intracellular stores, which triggers an influx of extracellular
calcium and activates the transcription of many genes, including
interleukin-2. Short-term
calcium fluxing is exaggerated in SLE, but long-term
calcium fluxing is diminished and may account for sub-optimal
interleukin-2 production. SLE T-cells have persistently hyperpolarized mitochondria associated with increased mitochondrial mass, high levels of
reactive oxygen species (ROS) and low levels of
ATP, which decrease activation-induced apoptosis and instead predispose T cells for
necrosis, thus stimulating
inflammation in SLE. The pentose phosphate pathway impacts the mitochondrial potential and represents a target for possible intervention.
Nitric oxide (NO) is a potential link to tie together the signaling and mitochondrial abnormalities in SLE. NO-induced mitochondrial biogenesis recapitulates the TCR-stimulated
calcium fluxing abnormalities of SLE T-cells. Since mitochondria can store
calcium, the increase in mitochondrial mass may be implicated in the aberrant
calcium fluxing in SLE T cells. The
mammalian target of rapamycin senses the mitochondrial potential and regulates
calcium release, serving as a novel target of treatment of SLE.