Involvement of immune cells in the anti-inflammatory action of
Cav3.2 channels inhibition
We then studied the mechanisms underlying the involvement of
Cav3.2 channels in edema development. One possible
explanation for the decreased edema observed in mice after
Cav3.2 channel inhibition was a reduction of the
neurogenic inflammation process (Xanthos and Sandkühler, 2014). Indeed,
inhibition of Cav3.2 located in C-LTMRs could reduce the
release of peripheral pro‐inflammatory neuropeptides in response to
antidromic nerve stimulation. To test this hypothesis, we assessed edema
development in Cav3.2Nav1.8 cKO mice.
No significant difference was observed in edema volume between
Cav3.2Nav1.8cKO mice and their control
Cav3.2GFP-flox KI littermates after
carrageenan injection (Figure 5A ) thereby excluding the
hypothesis of the neuronal nature of the anti-edematous effect of
Cav3.2 channel inhibition at least originating from
C-LTMR afferents. The other explanation was based on the involvement of
Cav3.2 channels expressed in immune cells in edema
formation. To test this, we designed chimeric mice with genetic deletion
of Cav3.2 only in hematopoietic cells (progenitor of
immune cells) or only in non-hematopoietic cells (Figure 5B ).
The absence of Cav3.2 channels specifically in the
immune system (WT recipient mice transplanted with KO immune cells)
reduced edema development, as in constitutive Cav3.2 KO
mice (KO recipient mice transplanted with KO immune cells)
(Figure 5C ). In contrast, edemas were restored in
Cav3.2 KO recipient mice receiving WT hematopoietic
cells (Figure 5C ). Consistently, the absence of
Cav3.2 channels only in hematopoietic cells
significantly reduced the production of IL-6, as in constitutive
Cav3.2 KO mice (Figure 5D ). Our results showed
that Cav3.2 channels expressed in immune cells are
strongly involved in edema development and IL-6 production.
To identify the nature of the immune cells involved in
Cav3.2-dependent edema development,
Cav3.2 channel expression was investigated in
macrophages and T cells. We used
Cav3.2GFP-flox KI mice to detect
Cav3.2 channel protein. Thus, bone marrow derived
macrophages (BMDM) and CD4 positive T cells (CD4+ T
cells) were obtained from the femurs and spleen, respectively, of
Cav3.2GFP-flox KI mice or control WT
mice and were labelled with an anti-eGFP antibody. Immunocytochemistry
revealed the expression of Cav3.2 channels in both BMDM
and lymphocyte CD4+ T cells (Figure 5E ).