Rosacea is a chronic inflammatory skin disorder of uncertain etiology. Evidence suggests the underlying pathogenesis is modulated by abnormal inflammatory and vascular responses. Thalidomide is a synthetic derivative acid with anti-inflammatory and anti-angiogenic properties. However, its effects on rosacea remain unknown.

To investigate the effects of thalidomide on the lesional alterations and molecular mechanisms in rosacea.

Mice were intradermally injected with LL37 to induce rosacea-like features and intraperitoneally administered with thalidomide. The severity of skin inflammation was evaluated. The mRNA levels of cytokines and chemokines associated with rosacea were assessed by qPCR. The number of CD4 positive infiltrated T helper cells and CD31 positive microvessels, and related-genes were measured by immunofluorescence, qPCR and ELISA. Moreover, the effect of thalidomide on inhibiting NF-κB activation was determined by immunofluorescence and western blot.

Our results showed that thalidomide significantly alleviated erythema and reduced inflammatory cell infiltration in dermis of LL37-induced rosacea-like mice. The production of cytokines and chemokines induced by LL37 was decreased by thalidomide in mice skin and HaCaT keratinocytes. Particularly, we showed thalidomide reduced CD4⁺ T helper cell infiltration and downregulated Th1- and Th17-polarizing genes. In addition, thalidomide treatment lowered the microvessel density and vascular endothelial growth factor (VEGF) expression. We further demonstrated that thalidomide suppressed NF-κB activation in LL37-treated skin and in TNF-α-stimulated HaCaT keratinocytes in vitro.

Our findings suggest thalidomide attenuates the inflammation and represses NF-κB activation in skin, which leads to assumptions that thalidomide may be a new therapeutic agent for rosacea.