Osteopontin, CCL5 and CXCL9 are independently associated with psoriasis, regardless of the presence of obesity.

Psoriasis is an autoimmune disease associated with the production of pro-inflammatory cytokines. The identification of these molecules in the pathogenesis of psoriasis facilitated the use of monoclonal antibodies to block their actions as a treatment for severe psoriasis. An increased inflammatory response has been documented in patients with obesity, a condition that is associated with the occurrence and severity of psoriasis. Osteopontin (OPN), TNF and CXCL9 levels are enhanced in patients with psoriasis, although OPN has been documented in the adipose tissue of obese patients without psoriasis. The prevalence of obesity is much higher in psoriasis patients compared with the general population. Thus, we aimed to evaluate the relationship between cytokine levels and psoriasis in the context of obesity. We compared OPN and CXCL9 plasma levels among 117 psoriasis patients and 27 healthy body mass index-matched subjects using ELISA. We also analyzed the TNF, CCL2 and CCL5 levels in a smaller subgroup of patients and matched controls. Median OPN, CCL5 and CXCL9 levels were significantly higher in psoriasis patients compared with the controls, independent of obesity. There was no difference between the median CCL2 levels in the psoriasis patients and the controls (P<0.05), although the CCL2 levels were elevated in obese patients compared with non-obese psoriasis patients (P<0.001). Facial involvement and the psoriasis area severity index (PASI) score were not associated (P<0.05) with OPN levels or elevated levels of chemokines. There was no significant correlation between the OPN and CXCL9 levels or the OPN and TNF levels in psoriasis patients. This work confirms that OPN, CCL5 and CXCL9 plasma levels are higher in psoriasis patients and provides evidence that their higher levels are not a consequence of obesity. Furthermore, the results demonstrate that OPN production is independent of TNF-α and CXCL9.