Air pollution aggravates renal ischaemia–reperfusion-induced acute kidney injury

Chronic kidney disease (CKD) has emerged as a significant global public health concern. Recent epidemiological studies have highlighted the link between exposure to fine particulate matter (PM_2.5) and a decline in renal function. PM_2.5 exerts harmful effects on various organs through oxidative stress and inflammation. Acute kidney injury (AKI) resulting from ischaemia–reperfusion injury (IRI) involves biological processes similar to those involved in PM_2.5 toxicity and is a known risk factor for CKD. The objective of this study was to investigate the impact of PM_2.5 exposure on IRI-induced AKI. Through a unique environmentally controlled setup, mice were exposed to urban PM_2.5 or filtered air for 12 weeks before IRI followed by euthanasia 48 h after surgery. Animals exposed to PM_2.5 and IRI exhibited reduced glomerular filtration, impaired urine concentration ability, and significant tubular damage. Further, PM_2.5 aggravated local innate immune responses and mitochondrial dysfunction, as well as enhancing cyclic GMP–AMP synthase-stimulator of interferon genes (cGAS–STING) pathway activation. This increased renal senescence and suppressed the anti-ageing protein klotho, leading to early fibrotic changes. In vitro studies using proximal tubular epithelial cells exposed to PM_2.5 and hypoxia/reoxygenation revealed heightened activation of the STING pathway triggered by cytoplasmic mitochondrial DNA, resulting in increased tubular damage and a pro-inflammatory phenotype. In summary, our findings imply a role for PM_2.5 in sensitising proximal tubular epithelial cells to IRI-induced damage, suggesting a plausible association between PM_2.5 exposure and heightened susceptibility to CKD in individuals experiencing AKI. Strategies aimed at reducing PM_2.5 concentrations and implementing preventive measures may improve outcomes for AKI patients and mitigate the progression from AKI to CKD. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.