Impact of mono-culture vs. Co-culture of keratinocytes and monocytes on cytokine responses induced by important skin sensitizers

Abstract

Sensitization to a contact allergen brings with it a lifelong risk to develop allergic contact dermatitis. Inflammation is an important part of the skin sensitizing mechanism, and understanding how different haptens stimulate the immune system, as well as the role played by different cell types present in skin, may be helpful for developing optimized in vitro models for risk assessment of new chemicals or mixtures. The aim of this study was to compare the cytokine profile following exposure of cells representing keratinocytes (HaCaT), monocytes (THP-1) and a co-culture of these cells to three clinically important skin sensitizers: cobalt (II) chloride (CoCl 2 ), methylisothiazolinone (MI) and p-phenylenediamine (PPD). Secretion of ten pro-inflammatory cytokines was measured using multiplexing. The results showed that the cytokine response differed substantially between the three cell assays. CoCl 2 caused an increase of IL-8 in HaCaT cells, while the induction of also IL-13 and IL-1b was observed in THP-1 cells and co-cultures. MI induced six cytokines in HaCaT cells but only IL-1b in the THP-1 cells and four cytokines in the co-culture. Interestingly, the IL-1b response was massive in the co-culture. PPD caused release of IL-1b in all three models as well as IL-8 in the co-culture. Control experiments with two non-sensitizers and irritants (lactic acid and sodium dodecyl sulfate) showed no effect on IL-8 or IL-1b in the co-culture. Taken together, results from this exploratory analysis show unique cytokine profiles dependent on the type of hapten and cell model. Importantly, all three haptens triggered secretion of IL-1b and IL-8 in a co-culture of HaCaT cells and THP-1 cells, representing the most robust test system.

Methodological Approaches To Assess Innate Immunity and Innate Memory in Marine Invertebrates and Humans

“…As a step forward in the validity of in vitro immunotoxicological assays, several co-culture assays are being developed and used ( Leonard et al, 2010 ; Noonan et al, 2019 ; Drasler et al, 2020 ; Karri et al, 2021 ). For example, an in vitro model of the inflamed intestinal mucosa, encompassing a three-dimensional co-culture of human intestinal epithelial cells (the cell line Caco-2) with human primary monocytes and monocyte-derived dendritic cells, can be used for assessing the effect of drugs and toxicants on gut inflammation ( Leonard et al, 2010 ).…”

Greater mechanistic understanding of the cutaneous pathogenesis of Stevens–Johnson syndrome/toxic epidermal necrolysis can shed light on novel therapeutic strategies: a comprehensive review

“…Traditional 2D skin models typically incorporate primary human or immortalized keratinocytes (such as HaCaTs), either in isolation, or co-cultured with other relevant cell types, (e.g. monocytes [ 110 ], or fibroblasts [ 111 ]). Such 2D models have been previously utilized to elucidate keratinocyte toxicity to molecules implicated in SJS/TEN pathogenesis, such as granulysin [ 26 ], TNF-α [ 78 ▪ ] and LL-37 [ 22 ].…”

Immunotoxicity In Vitro Assays for Environmental Pollutants under Paradigm Shift in Toxicity Tests

“…Cao et al found that, compared with THP-1 cultured alone, THP-1 co-cultured with KCs expressed more CD86 and CD54 on their surface after being exposed to skin sensitizers [54]. Karri et al also compared the effects of KCs (HaCaT) and monocyte (THP-1), cultured alone with their co-culture, on cytokine responses induced by important skin sensitizers [55]. In the co-culture model, the secretion of IL-1β and IL-8 was significantly triggered by all tested haptens, while non-sensitizers and stimulants were not.…”