Role of T CD4 cells, macrophages, C-low threshold mechanoreceptors and spinal Ca 3.2 channels in inflammation and related pain-like symptoms in murine inflammatory models.

Background And Purpose: T-type calcium channels, mainly the Ca 3.2 subtype, are important contributors to the nociceptive signalling pathway. We investigated their involvement in inflammation and related pain-like symptoms.

Experimental Approach: The involvement of Ca 3.2 and T-type channels was investigated using genetic and pharmacological inhibition to assess mechanical allodynia/hyperalgesia and oedema development in two murine inflammatory pain models. The location of Ca 3.2 channels involved in pain-like symptoms was studied in mice with Ca 3.2 knocked out in C-low threshold mechanoreceptors (C-LTMR) and the use of ABT-639, a peripherally restricted T-type channel inhibitor. The anti-oedema effect of Ca 3.2 channel inhibition was investigated in chimeric mice with immune cells deleted for Ca 3.2. Lymphocytes and macrophages from either green fluorescent protein-targeted Ca 3.2 or KO mice were used to determine the expression of Ca 3.2 protein and the functional status of the cells.

Key Results: Ca 3.2 channels contributed to the development of pain-like symptoms and oedema in the two murine inflammatory pain models. Our results provided evidence of the involvement of Ca 3.2 channels located on C-LTMRs and spinal cord in inflammatory pain. Ca 3.2 channels located in T cells and macrophages contribute to the inflammatory process.

Conclusion And Implications: Ca 3.2 channels play crucial roles in inflammation and related pain, implying that targeting of Ca 3.2 channels with pharmacological agents could be an attractive and readily evaluable strategy in clinical trials, to relieve chronic inflammatory pain in patients.