G2A Attenuates Propionibacterium acnes Induction of Inflammatory Cytokines in Human Monocytes.

BACKGROUND: Acne vulgaris is a disease of the pilosebaceous unit characterized by increased sebum production, hyperkeratinization, and immune responses to Propionibacterium acnes (PA). Here, we explore a possible mechanism by which a lipid receptor, G2A, regulates immune responses to a commensal bacterium. OBJECTIVE: To elucidate the inflammatory properties of G2A in monocytes in response to PA stimulation. Furthermore, our study sought to investigate pathways by which lipids modulate immune responses in response to PA. METHODS: Our studies focused on monocytes collected from human peripheral blood mononuclear cells, the monocytic cell line THP-1, and a lab strain of PA. Our studies involved the use of enzyme-linked immunosorbent, Western blot, reverse transcription polymerase chain reaction, small interfering RNA (siRNA), and microarray analysis of human acne lesions in the measurements of inflammatory markers. RESULTS: G2A gene expression is higher in acne lesions compared to normal skin and is inducible by the acne therapeutic, 13-cis-retinoic acid. In vitro, PA induces both the Toll-like receptor 2-dependent expression of G2A as well as the production of the G2A ligand, 9-hydroxyoctadecadienoic acid, from human monocytes. G2A gene knockdown through siRNA enhances PA stimulation of interleukin (IL)-6, IL-8, and IL-1ß possibly through increased activation of the ERK1/2 MAP kinase and nuclear factor kappa B p65 pathways. CONCLUSION: G2A may play a role in quelling inflammatory cytokine response to PA, revealing G2A as a potential attenuator of inflammatory response in a disease associated with a commensal bacterium.

Refractory pityriasis rubra pilaris treated with etanercept, adalimumab, or ustekinumab: A retrospective investigation.

Pityriasis rubra pilaris (PRP) is a rare, difficult to treat papulosquamous disorder that responds variably to retinoids and immunosuppression. Successful use of biologics for treating PRP has been described in the literature by case reports and a limited number of case series. To provide additional data, we retrospectively analyzed cases of PRP treated with biologics at our institution. We identified seven patients with a clear diagnosis of PRP treated with adalimumab, etanercept, and/or ustekinumab at our institution from January 1, 2014 to April 1, 2017. Six of seven patients had type I, adult acquired PRP, and one had type V atypical juvenile PRP. In response to tumor necrosis factor (TNF)-α inhibition, two patients had marked responses (>75% improvement in involved body surface area), while three patients failed to show any improvement on a TNF-α inhibitor. In two cases of PRP refractory to TNF-α inhibition, ustekinumab resulted in a partial response (<75% improvement) in one patient and no response in the other. Compared to other published data, our cohort was substantially more resistant to treatment with biologics, a finding which may provide valuable perspective for dermatologists managing refractory PRP in the future.