In vitro effects of curcumin on proinflammatory cytokines and expression of their genes in minor salivary gland tissue of patients with Sjogren's syndrome

Curcumin reduces disease severity and ameliorates lupus-like/Sjogren's Syndrome-like disease in mice model. The immunological basis of these effects is largely unknown. This study examined the effects of curcumin on pro-inflammatory cytokines secreted by minor salivary glands in patients with primary Sjogren's syndrome (pSS). Minor salivary gland (MSG) tissue samples were collected from patients undergoing biopsy for suspected pSS. The tissues were treated with phytohemagglutinin (PHA) alone as well as PHA with curcumin (30 mu M) and cultured in RPMI 1640 medium for 48 h at 37 degrees C in CO2 incubator. After the incubation period, culture supernatant and tissues were stored in the freezer (-80 degrees C). IL-6 levels were measured in supernatant by ELISA kit. Gene expressions of pro-inflammatory cytokines, namely IL-6, IL-8, TNF-alpha, IL-1 beta, IL-4, IL-10, IL-17, IL-21, and IFN-gamma, were measured by qPCR. IL-6 secretion levels and gene expressions were compared statistically between groups by Student's t test. Forty-seven patients were screened. Eight patients satisfied ACR/EULAR criteria for pSS. Seven patients with absent glandular inflammation and negative serology constituted sicca controls. These 15 subjects were included in final analysis. In pSS group, but not in controls, median IL-6 levels in supernatant were less in curcumin-treated as compared to PHA-alone subset [5.5 (0.7-1.3) vs 18.3 (12-32) ng/ml; p = 0.04]. mRNA expression levels of IL-6 and IL-1 beta were lower in curcumin-treated samples as compared to PHA alone, both amongst pSS and control groups (p = 0.0009 and p = 0.04, respectively). There was no difference in other cytokine gene expression levels between the subsets under the in vitro experimental conditions. In conclusion, curcumin reduced secretion of IL-6 levels by salivary gland tissue of patients with pSS. Curcumin also suppressed PHA-induced mRNA expression levels of IL-6 and IL-1 beta in MSG tissue of patients with pSS and controls.

Automated summary

This study found that Curcumin can reduce IL-6 secretion levels in salivary gland tissue of patients with pSS, as well as lower mRNA expression levels of IL-6 and IL-1 beta.