Comprehensive analysis of human keratinocyte and opportunistic pathogenic <i>Candida</i> interactions

The skin provides extensive protection against several pathogens. On its surface epithelial cells, or keratinocytes, respond to microbial stimuli primarily through the secretion of antimicrobial peptides and inflammatory cytokines. However, their alarming function is restricted to invading pathogenic organisms. Recent microbiome studies suggest that <i>Candida</i> species are natural colonisers of the human skin. However, discrepancies are present regarding the presence of <i>C. albicans</i> on the healthy skin, that is also frequently associated with cutaneous candidiasis. Therefore, here we aimed to investigate human keratinocyte responses to <i>C. albicans</i> and to another <i>Candida</i> species, <i>C. parapsilosis</i> - that is more likely to resemble skin commensals - in order to assess and compare the nature of skin epithelial cell responses to <i>Candida</i> species. Our results indicate that humoral, cellular and metabolic activities are more pronounced in the presence of <i>C. albicans</i>, than <i>C. parapsilosis</i>, suggesting a naturally occurring alarming response against this species.皮肤可对多种病原体提供广泛的防护。其表面的上皮细胞（keratinocytes，又称角质形成细胞）主要通过分泌抗菌肽与炎性细胞因子响应微生物刺激。不过，这类细胞的警报功能仅针对入侵的病原微生物。近期的微生物组研究表明，念珠菌属（Candida）物种是人类皮肤的天然定植菌群。然而，关于白色念珠菌（C. albicans）在健康皮肤表面的存在情况存在争议——该真菌也常与皮肤念珠菌病相关联。因此，本研究旨在探究人类角质形成细胞对白色念珠菌以及另一种念珠菌属物种近平滑念珠菌（C. parapsilosis，其更符合皮肤共生菌的特征）的应答反应，以此评估并比较皮肤上皮细胞对不同念珠菌属物种的应答本质。研究结果显示，相较于近平滑念珠菌，白色念珠菌存在时，体液、细胞及代谢相关活性的表现更为显著，这表明机体对该物种存在天然的警报应答反应。