Role of Cyclophilin D in cholesterol crystal-induced acute kidney injury

Li, Cong (2025): Role of Cyclophilin D in cholesterol crystal-induced acute kidney injury. Dissertation, LMU München: Faculty of Medicine

Abstract

Background: Cholesterol crystal embolism (CCE) is a severe complication of atherosclerosis. It occurs when cholesterol crystals (CC) are released from ruptured atherosclerotic plaques in larger arteries. These CC then migrate to small and medium-sized arteries in critical areas. Immune thrombi characterize this pathological process. These thrombi comprise activated platelets, neutrophils, extracellular DNA traps, collagen, and fibrin networks. Sustained activation of platelets and immune cells leads to the expansion of the thrombus, resulting in the obstruction of these arteries and subsequent ischemic failure in the affected tissues and organs. The involvement of kidney arteries in CCE results in acute kidney injury (AKI), which is marked by a rapid decline in glomerular filtration rate (GFR) and ischemic necrosis of tubular cells. A salient feature in this process is the substantial platelet stimulation that prompts the development of the cyclophilin D (CypD)-dependent mitochondrial permeability transition pore (MPTP) within platelet mitochondria, thus further promoting the activation of procoagulant platelet subpopulations. We hypothesize that CypD deficiency has the potential to reduce CC-induced kidney artery immune thrombosis by means of inhibition of the activation of these procoagulant platelet subsets. This, in turn, could lead to alleviation of the GFR loss and kidney infarction associated with CCE-induced AKI. Methods: To establish a CCE model, 10 mg/kg of CC were injected into the left kidney artery of both wild-type and CypD-deficient mice aged 6 to 8 weeks. GFR was measured 24 hours before and after surgery to assess kidney function, and mice were sacrificed 24 hours post-surgery for kidney analysis. Selected kidney tissues were stained with 2,3,5-triphenyltetrazolium chloride (TTC) to evaluate infarct size, while immunohistochemistry and immunofluorescence microscopy assessed infarct size and immune cell infiltration. Further in vitro experiments conducted using flow chambers explored the impact of CypD deficiency on CC-induced thrombosis and its interactions with immune cells. Furthermore, we investigated whether the administration of specific inhibitors—such as the CypD inhibitor cyclosporin A (CSA), the TMEM16F inhibitor niflumic acid (NFA), and the platelet integrin receptor αIIbβ3 inhibitor Tirofiban—prior to CCE model induction could mitigate acute kidney injury by reducing immune thrombosis. Results: CypD plays a pivotal regulatory role in the MPTP formation and opening, exerting a substantial influence on the activation and function of procoagulant platelets. CypD deficiency has been observed to mitigate CCE-induced acute kidney injury by diminishing kidney artery immune thrombosis. In our mouse model of CCE-induced AKI, CypD deficiency has been associated with a decrease in immune thrombus formation, fewer obstructed kidney arteries, reduced loss of GFR, diminished kidney swelling, and lessened kidney tissue infarction and tubular necrosis. Additionally, immune cell infiltration was significantly minimized, effectively reducing kidney injury resulting from CCE. Prophylactic administration of the CypD inhibitor CSA has been shown to mitigate kidney artery immune thrombosis and enhance kidney function in our CCE model. Furthermore, inhibitors targeting TMEM16F, a downstream protein of CypD, such as NFA, as well as the platelet integrin receptor αIIbβ3 inhibitor Tirofiban, have demonstrated efficacy in improving kidney function post-CCE. These findings underscore the potential of targeting CypD-mediated pathways and related therapeutic targets to enhance outcomes in CCE-induced kidney pathology. Conclusion: Our study elucidated the critical role of the CypD in alleviating CCE-induced acute kidney injury. We demonstrated that CypD knock out alleviates acute kidney inflammation, reduces loss, and minimizes immune thrombosis formation in the kidney artery induced by CCE. Furthermore, our study investigated the therapeutic potential of CypD inhibitors such as CSA, which significantly constricts kidney vessels and maintains GFR. Furthermore, our study identified that targeting specific signaling pathways, including TMEM16F and integrin receptors αIIbβ3, can reduce platelet activation and immune thrombosis, reducing kidney injury and offering significant therapeutic benefits. The current findings provide crucial insights into the pathophysiological mechanisms of CCE-induced kidney injury and offer promising therapeutic avenues for clinical application. In the context of kidney artery obstruction and atherosclerosis, the potential to modulate CypD activity and related pathways emerges as a pivotal strategy for the prevention and treatment of acute kidney injury.

• Item Type: Theses (Dissertation, LMU Munich)
• Subjects: 600 Technology, Medicine; 600 Technology, Medicine > 610 Medical sciences and medicine
• Faculties: Faculty of Medicine
• Language: English
• Date of oral examination: 11. July 2025
• 1. Referee: Anders, Hans-Joachim
• Signature of the printed copy: 0700/UMD 22399