Background/Purpose: Bcl11b, a zinc finger bi-functional transcription factor, is highly expressed in various tissues during development and differentiation, including stromal cells. It has been shown that Bcl11b has an impact on Th17 responses. Recently we found using a bioinformatic analysis that Bcl11b is down-regulated in psoriatic skin. In addition to Bcl11b, other transcription factors, such as NF-kB, are also involved in immune-mediated diseases that can be activated by cytokine stimulation. However, the mechanism of activation and regulation of pathways related to these transcription factors has not been identified.

To investigate the role of Bcl11b in the regulation of NF-kB pathways in keratinocytes under naïve and inflammatory conditions.

Methods: : HaCaT keratinocytes were cultured and Bcl11b was knocked down in these cells using the CRISPRi approach. qPCR and WB were performed to analyze the RNA and protein levels of Bcl11b, control genes, and NF-kB pathway genes. In addition, the effect of IL-17A, IL-23, TNF, IL-23/TNF, and IL-17A/IL-23 on the activation of the canonical and non-canonical NF-kB pathways in HaCaT keratinocytes was investigated in the presence or absence of Bcl11b.

Results: To mimic the lower expression of Bcl11b that has been found in different autoimmune diseases, Bcl11b was knocked down in keratinocytes, which was confirmed using q-PCR and WB. Gene expression analysis and/or WB of NF-kB pathways including NF-kB1, TNF, NF-kB2, RELB, and NIK indicated an upstream role of Bcl11b in both the canonical and non-canonical NF-kB pathways. We further analyzed these pathways under inflammatory conditions. Cytokine stimulation showed that the IL-17A, IL-17/IL-23, and IL-23/TNF can rescue the down-regulation of Bcl11b expression. None of these cytokines are able to activate the canonical NF-kB pathway under Bcl11b knockdown condition. Interestingly, IL-17A and IL-23/TNF, but not IL-23 or TNF alone, are able to activate the non-canonical NF-kB pathway in the absence of Bcl11b.

Conclusion: Here, we showed for the first time the role of Bcl11b and its interaction with the canonical and non-canonical NF-kB pathways in keratinocytes. Our data suggest that pro inflammatory cytokines have different effects on Bcl11b dependent activation of NF-kB pathways. Since Bcl11b acts both directly, and indirectly to promoter regions, this may impact its effect on the NF-kB pathways in different inflammatory conditions. Further studies are warranted to unravel the interaction of Bcl11b and these two NF-kB pathways.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-effect-of-inflammatory-conditions-on-the-regulation-of-canonical-and-non-canonical-nf-kb-pathways-via-bcl11b/