Insulin-like growth factor-1 induces hyperproliferation of PKD1 cystic cells via a Ras/Raf dependent signalling pathway

Autosomal dominant polycystic kidney disease (ADPKD) largely results from mutations in the PKD1 gene leading to hyperproliferation of renal tubular epithelial cells and consequent cyst formation. Rodent models of PKD suggest that the multifunctional hormone insulin-like growth factor-1 (IGF-1) could play a pathogenic role in renal cyst formation. In order to test this possibility, conditionally immortalized renal epithelial cells were prepared from normal individuals and from ADPKD patients with known germline mutations in PKD1. All patient cell lines had a decreased or absence of polycystin-1 but not polycystin-2. These cells had an increased sensitivity to IGF-1 and to cyclic AMP, which required phosphatidylinositol-3 (PI3)-kinase and the mitogen-activated protein kinase, extracellular signal-regulated protein kinase (ERK) for enhanced growth. Inhibition of Ras or Raf abolished the stimulated cell proliferation. Our results suggest that haploinsufficiency of polycystin-1 lowers the activation threshold of the Ras/Raf signalling system leading to growth factor-induced hyperproliferation. Inhibition of Ras or Raf activity may be a therapeutic option for decreasing tubular cell proliferation in ADPKD

Perioperative platelet and monocyte activation in patients with critical limb ischemia

BackgroundPatients with critical limb ischemia (CLI) have a high rate of adverse cardiovascular events, particularly when undergoing surgery. We sought to determine the effect of surgery and vascular disease on platelet and monocyte activation in vivo in patients with CLI.MethodsAn observational, cross-sectional study was performed at a tertiary referral hospital in the southeast of Scotland. Platelet and monocyte activation were measured in whole blood in patients with CLI scheduled for infrainguinal bypass and compared with matched healthy controls, patients with chronic intermittent claudication, patients with acute myocardial infarction, and those undergoing arthroplasty (n = 30 per group). Platelet and monocyte activation were quantified using flow cytometric assessment of platelet-monocyte aggregation, platelet P-selectin expression, platelet-derived microparticles, and monocyte CD40 and CD11b expression.ResultsCompared with those with intermittent claudication, subjects with CLI had increased platelet-monocyte aggregates (41.7% ± 12.2% vs 32.6% ± 8.5%, respectively), platelet microparticles (178.7 ± 106.9 vs 116.9 ± 53.4), and monocyte CD40 expression (70.0% ± 12.2% vs 52.4% ± 15.2%; P < .001 for all). Indeed, these levels were equivalent (P-selectin, 4.4% ± 2.0% vs 4.9% ± 2.2%; P > .05) or higher (platelet-monocyte aggregation, 41.7% ± 12.2% vs 33.6% ± 7.0%; P < .05; platelet microparticles, 178.7 ± 106.9 vs 114.4 ± 55.0/μL; P < .05) than in patients with acute myocardial infarction. All platelet and monocyte activation markers remained elevated throughout the perioperative period in patients with CLI (P < .01) but not those undergoing arthroplasty.ConclusionsPatients undergoing surgery for CLI have the highest level of in vivo platelet and monocyte activation, and these persist throughout the perioperative period. Additional antiplatelet therapy may be of benefit in protecting vascular patients with more severe disease during this period of increased risk.Clinical RelevancePeripheral arterial disease is increasingly common and is associated with a significant risk of cardiovascular complications, especially at the time of surgery. Despite this, patients are poorly provided with evidence-based therapies such as antiplatelet and lipid-lowering medications. Platelets play a key role in the pathogenesis of atherothrombosis, with elevated levels of in vivo platelet activation prognostic of adverse clinical events. This study demonstrates, for the first time to our knowledge, significantly greater levels of platelet activation in patients with severe peripheral arterial disease compared with patients with acute myocardial infarction or patients undergoing other moderate- to high-risk surgical procedures. This further emphasizes the need for improved risk stratification and cardioprotection of this vulnerable group