Objectives: A key mediator in cold-sensation is the protein transient receptor potential melastatin 8 (TRPM8), which is expressed on sensory nerves and cutaneous blood vessels. These receptors are activated by cold temperatures and play a key role in body thermoregulation. Cold sensitivity and Raynaud's phenomenon are frequent clinical features in scleroderma, and are thought to be secondary to a local defect in cutaneous thermoregulation. We investigated whether autoantibodies targeting TRPM8 were present in the sera of patients with scleroderma as evidence for a possible mechanism for an acquired immune mediated defect in thermoregulation.
Methods: Sera from 50 well-characterised scleroderma patients with Raynaud's phenomenon were studied. TRPM8 autoantibodies were assayed as follows: 1. immunoprecipitation with 35S-methionine-labelled TRPM8 generated by in vitro transcription and translation, 2. immunoblotting lysates made from cells transiently transfected with TRPM8 cDNA, 3. Immunoprecipitation of TRPM8 transfected lysates with detection by blotting and 4. flow cytometry.
Results: Fifty scleroderma patients with Raynaud's phenomenon (41 female, 39 Caucasian, 23 with limited scleroderma, and 20 with history of cancer) were studied. Four different methods to assay for TRPM8 antibodies were set up, optimised and validated using commercial antibodies. All 50 scleroderma patients' sera were assayed using each of the above methods, and all were negative for TRPM8 autoantibodies.
Conclusions: Antibodies against TRPM8 are not found in scleroderma patient sera, suggesting that the abnormal cold sensitivity and associated abnormal vascular reactivity in scleroderma patients is not the result of an immune process targeting TRPM8.