IL-33 receptor ST2 deficiency attenuates renal ischaemia–reperfusion injury in euglycaemic, but not streptozotocin-induced hyperglycaemic mice

Partial reduction of interleukin-33 signaling improves senescence and renal injury in diabetic nephropathy

Diabetic nephropathy (DN) is a frequent and costly complication of diabetes with limited understandings of mechanisms and therapies. Emerging evidence points to the important roles of interleukin-33 (IL-33) in acute kidney injury, yet its contribution to DN is still unclear. We here found a ubiquitous increase of IL-33 and its receptor (ST2) in murine models and patients with DN. Surprisingly, both IL-33 and ST2 knockdown aggravated renal lesions in DN, while overexpression of IL-33 also exacerbated the condition. Further population-based analyses revealed a positive correlation of IL-33 expression with renal dysfunction in DN patients. Individuals with high IL-33 expression-related polygenic risk score had a higher DN risk. These findings confirmed the harmful effects of IL-33 on DN. Conversely, endogenous and exogenous partial reduction of IL-33 signaling conferred renoprotective effects in vivo and in vitro. Mechanistically, IL-33 induced senescence by regulating cell cycle factors in HK-2 cells, and accordingly senescence led to renal cell damage through the secretion of senescence-related secretory phenotype (SASP) including IL-33 and prostaglandins. Together, elevated IL-33 accelerates cellular senescence to drive DN possibly by SASP production, while a partial blockage improves renal injury and senescence. Our findings pinpoint a possible and new avenue for DN interventions.

Pathophysiologic role of Interleukin-33/ST2 in Sjögren's syndrome

Interleukin-33 (IL-33) is a member of the IL-1 family and has dual functions as a nuclear factor as well as a cytokine. The pivotal role of IL-33 as an active player contributing to aberrant local and systemic damage has been highlighted in several inflammatory and autoimmune diseases. Primary Sjögren's syndrome (pSS) is an autoimmune disease characterized by dry eyes and mouth syndrome due to local dysfunctions of exocrine glands, but also accompanied with systemic manifestations. The pathophysiology of pSS has been advocated as a conjecture of activated B and T cells as well as the production of inflammatory cytokines and autoantibodies, driving epithelial tissue damage and disease progression. In pSS, IL-33 is released in the extracellular space from damaged salivary cells upon pro-inflammatory stimuli and/or dysfunction of epithelial barrier. Counter-regulatory mechanisms are initiated to limit the pro-inflammatory actions of IL-33 as portrayed by an increase in the decoy receptor for IL-33, the soluble form of ST2 (sST2). In pSS and associated diseases, the levels of IL-33 are significantly elevated in the serum or tears of patients. Mechanistically, IL-33 acts in synergy with IL-12 and IL-23 on NK and NKT cells to boost the production of IFN-γ contributing to inflammation. TNF-α, IL-1β and IFN-γ in turn further increase the activation of IL-33/ST2 pathway, thereby constituting a vicious inflammatory loop leading to disease exacerbation. IL-33/ST2 axis is involved in Sjögren's syndrome and opens new perspectives as therapeutic target of one of the culprits in the inflammatory perpetuation.

Emerging Roles of Interleukin-33-responsive Kidney Group 2 Innate Lymphoid Cells in Acute Kidney Injury

Interleukin (IL)-33, a member of the IL-1 family of cytokines, is involved in innate and adaptive immune responses. IL-33 triggers pleiotropic immune functions in multiple types of immune cells, which express the IL-33 receptor, ST2. Recent studies have revealed the potential applications of IL-33 for treating acute kidney injury in preclinical animal models. However, IL-33 and IL-33-responding immune cells are reported to exhibit both detrimental and beneficial roles. The IL-33-mediated immunomodulatory functions have been investigated using loss-of-function approaches, such as IL33-deficient mice, IL-33 antagonists, or administration of exogenous IL-33 recombinant protein. This review will discuss the key findings on IL-33-mediated activation of kidney resident group 2 innate lymphoid cells (ILC2s) and summarize the current understanding of the differential functions of endogenous IL-33 and exogenous IL-33 and their potential implications in treating acute kidney injury.

The role of activation of KАTP channels on hydrogen sulfide induced renoprotective effect on diabetic nephropathy

This work aims to investigate the renal effect of hydrogen sulfide (H₂ S), in the experimentally induced diabetic nephropathy, besides the role of activation of АТP-sensitive potassium (K_АTP ) channel in that effect. Thirty-two adult male albino rats randomly divided into four groups: Control, streptozotocin-induced diabetic (diabetic nephropathy [DN]), DN+NaHS (the H₂ S inducer), and DN+NaHS+Glibenclamide (a selective K_АTP channel blocker) groups. Results showed that kidney functions in the diabetic group improved by NaHS proved by the significant decrease in the measured renal injury markers when compared with the diabetic group with an obvious role of inflammation and oxidative stress. However, the improved kidney functions produced by NaHS was reduced by the combination with Glibenclamide. Glibenclamide combination led also to a significant increase in renal total antioxidant capacity, in addition to a significant decrease in renal total nitric oxide (NO) level. Аccordingly, the results from the present work revealed that the renoprotective effects of H₂ S in the case of DN through its effects on renal tissue antioxidants and NO can be partially dependent on activation of K_АTP channels, while its effect on renal tissue proinflammatory cytokines is independent of it.