Supervisors info:
Αϊδίνης Βασίλης, Ερευνητής Α’, Ερευνητικό Κέντρο Βιοϊατρικών Επιστημών "Αλέξανδρος Φλέμινγκ"
Τζιούφας Αθανάσιος, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Ανδρεάκος Ευάγγελος, Ερευνητής Α’, ΙΙΒΕΑΑ
Summary:
Renal tubular epithelial cells (TECs) are the cells lining the nephrons, the functional units of the kidney. They selectively transport minerals, organic compounds, and water into and out of the tubular fluid. TECs are vulnerable to injuries and therefore amenable to cell death, mitochondrial dysfunction, oxidative stress, senescence, and pro-inflammatory cytokine secretion resulting in abrogation of the tubular function. Repair mechanisms may lead to the reversal of the damage or become maladaptive and lead to tubulointerstitial fibrosis. Despite diverse etiologies, renal diseases develop the shared pathological feature of renal fibrosis as they progress to end-stage renal failure.
Lysophosphatidic acid (LPA) is a bioactive lipid mediator that triggers several physiological events such as cell proliferation, survival, migration, and motility mediated by binding to specific G-protein-coupled receptors (LPAR1-6). Depending on the type of stressor exposed to the kidneys, the site of production, and the abundance of the different LPA chemical forms, LPA can play a fundamental role in promoting pathological alterations of cell structure and function.
In this project, given the crucial role of TECs in renal fibrosis and the implication of LPA in other fibrotic diseases, we delve into the effect of LPA on renal TECs. In previous studies of our lab, the protein levels of 32 cytokines and 27 phosphoproteins related to the immune system, produced by human renal tubular epithelial cells (HKC-8) upon LPA stimulation, were monitored with Multiplex Elisa. The preliminary results suggested that LPA induces the statistically significant upregulation of the intercellular adhesion molecule 1 (ICAM1), interleukin 6 (IL6), C-C motif chemokine ligand 2 and 3 (CCL2, CCL3), C-X-C motif chemokine ligand 8 and 10 (CXCL8/IL8, CXCL10). Here, we stimulate HKC-8 with different concentrations of LPA and for various time points, and we analyze the mRNA induction of critical immune system mediators. CCL2, CCL3, CXCL8, ICAM1, and IL6 mRNA levels are induced upon stimulation with 10 μM LPA obtaining the highest values four hours post-stimulation. Given that all these cytokines, chemokines, and adhesion molecules are pro-inflammatory, LPA emerges as a pro-inflammatory stimulus for HKC-8.
Furthermore, by employing inhibitors specific to LPA-induced signaling hubs, we offer some mechanistic insight into the contribution of LPA to kidney-related chronic inflammation: CREB1, MEK/ERK, and NFκB mediate CCL2, CCL3, CXCL8, and ICAM1 mRNA expression in hTECs upon stimulation with LPA. Concurrently, our results suggest that the LPA-induced CCL3 and ICAM1 expression from HKC-8 is mediated by c-JUN, too. Concerning the LPARs implicated in the LPA-induced signaling cascade, we show that LPAR2 is the dominant LPAR in these cells. Upon the LPA-stimulation, IL6 expression is mediated by this receptor and LPAR1/3, whereas the expression of CCL3, and CXCL8 is linked to LPAR1/3. Finally, through an inhibitor targeting specific G-proteins, we exclude the possibility of Gi/o implication in the expression of the immune-related molecules of interest. Overall, in this project, we put forward the challenging initiative of rewiring in vitro the LPA-induced signaling network that leads to the production of pro-inflammatory factors closely related to renal fibrosis.
Keywords:
Lysophosphatidic acid, Human Proximal Tubular Epithelial Cells, Pro-inflammatory stimulus, Signaling hubs, Renal pathology
