Effect of Curcumin on pro-inflammatory cytokines in primary Sjögren’s Syndrome

Abstract Introduction Curcumin reduces disease severity and ameliorates lupus-like/ Sjögren’s Syndrome-like disease in mice model. The immunological basis of these effects is unknown. This study examined the effect of curcumin on pro-inflammatory cytokines secreted by salivary gland in patients with primary Sjögren’s syndrome (pSS). Methods Minor salivary gland (MSG) tissue was collected from patients undergoing biopsy for suspected pSS. The tissues were treated with phytohemagglutinin (PHA) alone as well as PHA with curcumin (30μM) and cultured in RPMI 1640 medium for 48 hours at 37°C in CO2 incubator. After the incubation period, culture supernatant and tissue were stored in the freezer (−80 °C). IL-6 levels were measured in supernatant by ELISA kits. Expression of pro-inflammatory cytokines, IL-6, IL-8, TNF-α, IL-1β, IL-4, IL10, IL-17 IL-21, and IFN-γ was done by qPCR. Differences between groups were tested by Student’s t-test. Results Forty seven patients were recruited. Eight patients satisfied ACR/EULAR criteria for pSS. Seven patients with absent glandular inflammation and negative serologies constituted sicca controls. In pSS group, but not in controls, median IL-6 levels in supernatant was less in curcumin treated as compared to PHA alone [5.5 (0.7 – 1.3) vs 18.3 (12–32) ng/ml;p=0.04]. mRNA expression levels of IL-6 and IL-1β were lower in curcumin treated groups as compared to PHA alone in both cases and controls (p= 0.0009 & p=0.04 respectively). There was no difference in other cytokine levels between the treatment groups. Conclusion Curcumin reduces secretion of IL-6 levels in salivary gland tissue of patients with pSS. Curcumin suppressed PHA induced mRNA expression levels of IL-6 and IL-1β in MSG tissue of pSS and controls.