Biology subjects

Galichon, P.

Publications and source records attributed to Galichon, P..

5 recordsLinked to original sources

bioRxiv2024

The preferential injury of outer renal medulla after ischemia-reperfusion relies on high oxidative metabolism

Acute kidney injury (AKI) is a prevalent and significant complication in critically ill patients, and its management remains a considerable challenge. The kidney is a highly metabolic organ, consuming and producing substantial amounts of ATP, mainly through mitochondrial oxidative phosphorylation. Recently, mitochondrial dysfunction has been identified as a key factor in the pathophysiology of AKI and the progression to chronic kidney disease. The kidney is a complex organ, comprising millions of structural and functional units. These nephrons are composed of different cell types dwelling within specific metabolic microenvironment. Whether the metabolic spatialization in the kidney has consequences on tubular injury distribution and severity remains unclear. In this study, we identified the high metabolic rate of the outer stripe of the outer medulla (OSOM) and its substrate preference flexibility, relying on both glycolysis and fatty acid oxidation (FAO) to fulfill its ATP demands. We demonstrated that the OSOM is susceptible to mitochondrial and FAO impairment induced by propofol, the most used sedative in intensive care settings, which exacerbates tubular injury during AKI. In the clinical setting, the cumulative dose of propofol is positively correlated with oxidative metabolism disruption and histological and function outcomes in renal allograft recipients. Finally, we found that the loop of Henle, the OSOM major constituent, was the most injured segment during AKI in patients. This study shows how renal metabolic spatialization impacts tubular injury severity. We identified the OSOM as the most metabolically active and the most injured region of the kidney both in humans and mice. We demonstrated that propofol is a potent inhibitor of renal mitochondrial function and FAO exacerbating tubular injury in the OSOM upon IRI. Translational StatementO_LIAerobic metabolism is basally enhanced in the renal OSOM, including the S3 proximal tubule, the thick ascending limb of the loop of Henle and Distal Convoluted Tubule C_LIO_LIPT cells as well as TAL cells are significantly targeted by injury in human AKI. C_LIO_LIPropofol impairs renal mitochondrial function worsening tubular injury during ischemia reperfusion. C_LI

physiology↗

bioRxiv2022

Protective role of podocytic IL-15/STAT5 pathway in experimental focal and segmental glomerulosclerosis

During glomerular diseases, podocyte-specific pathways can modulate the intensity of the lesions and prognosis. The therapeutic targeting of these pathways could thus improve the management and prognosis of chronic kidney diseases. The Janus Kinase/ Signal Transducer and Activator of Transcription (JAK/STAT) pathway, classically described in immune cells, has been recently described in intrinsic kidney cells. Here, we show, for the first time, that STAT5 is activated in human podocytes in focal segmental glomerulosclerosis (FSGS). Additionally, Stat5 podocyte-specific inactivation aggravates the functional and structural alterations in a mouse model of FSGS. This could be due, at least in part, to an inhibition of the autophagic flux. Finally, Interleukin 15 (IL-15), a classical activator of STAT5 in immune cells, increases STAT5 phosphorylation in human podocytes and its administration alleviates glomerular injury in vivo by maintaining the autophagy flux in podocytes. In conclusion, activating podocytic STAT5 with commercially available IL-15 represents a new therapeutic avenue with the potential for FSGS.

pathology↗

bioRxiv2020

Orphan nuclear receptor COUP-TFII drives the myofibroblast metabolic shift leading to fibrosis

Recent studies demonstrated that metabolic disturbance, such as augmented glycolysis, contributes to fibrosis. The molecular regulation of this metabolic perturbation in fibrosis, however, has been elusive. COUP-TFII (also known as NR2F2) is an important regulator of glucose and lipid metabolism. Its contribution to organ fibrosis is undefined. Here, we found increased COUP-TFII expression in myofibroblasts in kidneys of patients with chronic kidney disease, fibrotic lungs of patients with idiopathic pulmonary fibrosis, fibrotic human kidney organoids, and fibrotic mouse kidneys after injury. Genetic ablation of COUP-TFII in mice resulted in attenuation of injury-induced kidney fibrosis. A non-biased proteomic study revealed the suppression of fatty acid oxidation and the enhancement of glycolysis pathways in COUP-TFII overexpressing fibroblasts. Overexpression of COUP-TFII in fibroblasts was sufficient to enhance glycolysis and increase alpha smooth muscle actin (SMA) and collagen1 levels. Knockout of COUP-TFII decreased glycolysis and collagen1 levels in fibroblasts. Chip-qPCR assays revealed the binding of COUP-TFII on the promoter of PGC1, a critical regulator of mitochondrial genesis and oxidative metabolism. Overexpression of COUP-TFII reduced the cellular level of PGC1. In conclusion, COUP-TFII mediates fibrosis by serving as a key regulator of the shift in cellular metabolism of interstitial pericytes/fibroblasts from oxidative respiration to aerobic glycolysis. The fibrogenic response may share a common pathway in different organ injury and failure. Targeting COUP-TFII serves as a novel treatment approach for mitigating fibrosis in chronic kidney disease and potential other organ fibrosis.

cell biology↗

bioRxiv2020

Regulation of intracellular energy supplies by cell cycle kinetics using a single cell approach.

Both proliferative and anti-proliferative pathways are induced after acute kidney injury. The consequences of proliferation on energy homeostasis and cell viability are unknown. We hypothesized that proliferation regulation is an important determinant of epithelial fate after acute kidney injury. We studied the relationship between proliferation and cell viability in kidney tubular cells. We then analyzed the effect of proliferation on the intracellular ATP/ADP ratio. Finally, we used transcriptomic data from transplanted kidneys to study the relationship between cell proliferation and energy production with different clinical evolutions. We found that proliferation is associated with decreased survival after toxic or energetic stresses in kidney proximal tubular cells. In vitro, we found that the ATP/ADP ratio oscillates reproducibly throughout the cell cycle, and that proliferation is instrumental to an overall decrease in intracellular ATP/ADP ratio. In vivo, in injured kidneys, we found that proliferation was strongly associated with a specific decrease in the expression of the mitochondria-encoded genes of the oxidative phosphorylation pathway as opposed to the nucleus-encoded ones. These observations suggest that mitochondrial function is the limiting factor for energy production in kidney cells proliferating after injury. The association of increased proliferation and decreased mitochondrial function was associated with poor renal outcomes. In summary, we show that proliferation is an energy demanding process impairing the cellular ability to cope with a toxic or ischemic injury, identifying the association of proliferative repair and metabolic recovery as indispensable and interdependent features for successful kidney repair. One Sentence SummaryProliferation decreases energy availability in kidney epithelial cells and is associated with enhanced cell death and chronic kidney disease in case of a superimposed metabolic stress.

cell biology↗

bioRxiv2019

Impaired renal gluconeogenesis is a major determinant of acute kidney injury associated mortality

Nature letterAcute Kidney Injury (AKI) is strongly associated with adverse outcome and mortality independently of the cause of renal damage1-3. The mechanisms determining the deleterious systemic effects of AKI are poorly understood and specific interventions, including optimization of renal replacement therapy, had a marginal effect on AKI-associated mortality in clinical trials4-8. The kidney contributes to up to 40% of systemic glucose production by gluconeogenesis during fasting and stress conditions, mainly synthesized from lactate in the proximal tubule9-12, rendering this organ a major systemic lactate disposal13. Whether kidney gluconeogenesis is impaired during AKI and how this might influence systemic metabolism remains unknown. Here we demonstrate that glucose production and lactate clearance are impaired during human AKI using renal arteriovenous catheterization in patients. Using single cell transcriptomics in mice and RNA sequencing in human biopsies, we show that glycolytic and gluconeogenetic pathways are modified during AKI in the proximal tubule specifically, explaining the metabolic alterations. We further demonstrate that impaired renal gluconeogenesis and lactate clearance during AKI are major determinants of systemic glucose and lactate levels in critically ill patients. Most importantly, altered glucose metabolism in AKI emerged as a major determinant of AKI-associated mortality. Thiamine supplementation restored renal glucose metabolism and substantially reduced AKI-associated mortality in intensive care patients. This study highlights an unappreciated systemic role of renal glucose and lactate metabolism in stress conditions, delineates general mechanisms explaining AKI-associated mortality and introduces a potential therapeutic intervention for a highly prevalent clinical condition with limited therapeutic options.

cell biology↗