Background: Chronic kidney disease (CKD) affects over 1 in 10 Australian adults, yet effective targeted therapies to halt disease progression are lacking. CKD pathology is driven by a complex cycle of ischemic injury, inflammation, and maladaptive repair. While inflammasomes are known to drive the release of pro-inflammatory cytokines IL-1β and IL-18, their specific role in renal proximal tubular epithelial cells (RPTECs) – which represent 66% of all kidney cells – remains poorly characterised. Therefore, this study determined the expression profile and activation capacity of major inflammasomes in primary human RPTECs.
Methods: Primary human RPTECs isolated from three donors (2M, 1F) were cultured in renal epithelial growth medium (Lonza Biosciences). Basal gene and protein expression were analysed via RT-qPCR and immunoblotting. To examine functionality, RPTECs were treated with specific inflammasome activators; downstream activation and cell death were assessed using cytokine ELISA, LDH release, and propidium iodide (PI) uptake assays.
Results: RT-qPCR revealed RPTECs constitutively express transcripts for NLRP1 and NLRP3 sensors, alongside downstream ASC, CASP1, GSDMD, IL1B, and IL18. Immunoblotting demonstrated a similar pattern of protein expression, notably NLRP1 was strongly expressed; however, NLRP3 protein was undetectable. Functionally, specific NLRP1 activators induced secretion of mature IL-1β, whereas NLRP3 activators had minimal effect. Importantly, LPS priming was not required for IL-1β release. Furthermore, LDH and PI assays demonstrated that this activation occurred in the absence of lytic cell death.
Conclusion: This study demonstrates for the first time that primary human RPTECs express inflammasome machinery, with a specific functional role for NLRP1. Unlike myeloid cells, RPTEC NLRP1 activation is priming-independent and sub-lytic, suggesting a specialized mechanism for sustaining chronic tubular inflammation. These findings identify the NLRP1 inflammasome as a novel, targetable driver of cytokine release in the kidney and a potential therapeutic candidate for slowing CKD progression.