As part of the innate immune system leucocytes play a major role in the inflammatory response. Neutrophil granulocytes circulate in the blood vessel system until they are activated and recruited to inflamed tissues. Attracted by cytokines they transmigrate the endothelium and migrate into affected tissue.This signal transduction utilizes Ca²⁺ transients. On our way to identify the involved Ca²⁺ entry channels we investigated the role of TRPC1 and TRPC6, members of the transient receptor potential (TRP) channel family.

We studied the impact of either TRPC1 or TRPC6 knockout on migration of murine neutrophils in 2- and 3-dimensional matrices and in a microfluidic vasculature model with time-lapse videomicroscopy. For chemotactic or chemokinetic stimulation the bacterial N-formylated peptide fMLP was used as end-target chemoattractant and KC or an ex vivo chemokine-cocktail were applied as intermediary chemoattractants. Receptor-signaling was studied via western blot and Ca²⁺-influx was analyzed by Fura-2 Ca²⁺ measurements.

Chemotaxis of TRPC1^-/- and TRPC6^-/- neutrophils with the chemokine-cocktail and KC was strongly impaired while chemotaxis towards fMLP was reduced in TRPC1^-/- and unaffected in TRPC6^-/- cells. TRPC6 was assigned to CXCR2 signaling and western blot analysis revealed an impaired phosphorylation of Akt/PKB in TRPC6^-/- cells. Intracellular Ca²⁺ imaging showed reduced Ca²⁺ transients after intermediary chemokine stimulation.

Our findings indicate that both TRPC1 and TRPC6 are involved in neutrophil recruitment. TRPC1 and TRPC6 are components of intermediary chemoattractant signaling whereas TRPC1 is additionally involved in end-target signaling pathways.