Canine progenitor epidermal keratinocytes express various inflammatory markers, including interleukin-8 and CD40, which are affected by certain antibiotics

Background: Bacterial skin infections are common in dogs and humans. Keratinocytes have phenotypic features of nonprofessional antigen-presenting cells and express various cytokines. However, little is known about the effects of antibiotics on inflammatory markers in canine keratinocytes. Hypothesis/Objectives: To investigate inflammatory markers in canine progenitor epidermal keratinocytes (CPEKs) and to determine the effects of selected antibiotics on these markers. Methods: The CPEKs were exposed for 2-24 h to three concentrations of amoxicillin, cefalexin, sulfadimethoxine, sulfamethoxazole (or its nitroso metabolite), amikacin or enrofloxacin. Enzyme-linked immunosorbent assay (ELISA) and immunocytochemistry were used to detect major histocompatibility complex (MHC) II. CD40 and CXCR1 [interleukin (IL)-8 receptor] were detected using ELISA. Secreted cytokines/chemokines were quantified using a multiplex kit. Results: No MHC II protein was detected. CD40 protein was found at 24 h, with levels being significantly increased by enrofloxacin. The CPEKs secreted no detectable monocyte chemotactic protein-1; undetectable to low (picogram per millilitre range) concentrations of IL-6, IL-7, IL-10, IL-15, tumour necrosis factor-α, interferon-γ and granulocyte-macrophage colony-stimulating factor; and high (nanogram per millilitre range) concentrations of IL-8. Levels of IL-8 increased over 24 h following cell proliferation. They were significantly increased by enrofloxacin after 8 h, and by cefalexin, sulfadimethoxine, sulfamethoxazole, its nitroso metabolite and enrofloxacin after 24 h. The CPEKs expressed CXCR1. Conclusions and clinical importance: Canine progenitor epidermal keratinocytes express various inflammatory proteins, with expression profiles being affected by certain antibiotics. This supports previous work showing keratinocytes to be mediators of inflammation and demonstrates the potential pro-inflammatory effects of certain antibiotics in the skin.