Hidradenitis suppurativa (HS) is associated with dysregulated immune responses including altered expression of cytokines, chemokines, and antimicrobial peptides and proteins (AMPs).To evaluate the expression of NOD2 and related factors in HS skin samples and keratinocyte cultures. We performed RT-PCR for NOD2, RIP2, CARL, SKALP/elafin, human ß-defensin 2 (hBD2), LL37, psoriasin, RNAse7 in lesional and non-lesional skin of 19 HS patients and keratinocyte cultures (unstimulated, MDP-stimulated, PAM-stimulated) from and non-lesional skin. We observed significantly elevated mRNA expression for NOD2 (P = 0.0039), hBD2 (P = 0.018), RNase7 (P = 0.0003), psoriasin (P = 0.0053), and SKALP/elafin (P = 0.020) in lesional skin when compared to non-lesional skin. We found a significant correlation between NOD2 mRNA and hBD2 (r = 46; P = 0.039), psoriasin (r = 0.67; P = 0.0016), SKALP/elafin (r = 0.65; P = 0.0026). In unstimulated, PAM-stimulated, and MDP-stimulated normal keratinocytes, NOD2, RIP2, CARL, and SKALP/elafin expression significantly (P < 0.05) increased from 6 h to 48 h. In unstimulated, PAM-stimulated, and MDP-stimulated HS keratinocytes, RIP2, CARL, and SKALP/elafin expression significantly (P < 0.05) declined from 6 h to 48 h. mRNA expression of HS keratinocytes at 6 h was significantly increased for NOD2 (unstimulated, PAM, MDP), CARL (unstimulated, PAM, MDP), and SALP/elafin (unstimulated, PAM) as compared to normal keratinocytes. We have shown for the first time that the NOD2 signalling is activated in HS and might contribute to the pathogenesis via induction of AMPs and activation of other pathways such as NFκB signalling.
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