The results suggest that, in addition to its well-known erythropoietic effects, EPO inhibits apoptotic cell death, enhances tubular epithelial regeneration and promotes renal functional recovery in hypoxic or ischaemic acute renal injury.

The cardiomyocyte circadian clock directly regulates multiple myocardial functions in a time-of-day-dependent manner, including gene expression, metabolism, contractility, and ischemic tolerance. These same biological processes are also directly influenced by modification of proteins by monosaccharides of O-linked ␤-N-acetylglucosamine (O-GlcNAc). Because the circadian clock and protein O-GlcNAcylation have common regulatory roles in the heart, we hypothesized that a relationship exists between the two. We report that total cardiac protein O-GlcNAc levels exhibit a diurnal variation in mouse hearts, peaking during the active/awake phase. Genetic ablation of the circadian clock specifically in cardiomyocytes in vivo abolishes diurnal variations in cardiac O-GlcNAc levels. These time-ofday-dependent variations appear to be mediated by clock-dependent regulation of O-GlcNAc transferase and O-GlcNAcase protein levels, glucose metabolism/uptake, and glutamine synthesis in an NAD-independent manner. We also identify the clock component Bmal1 as an O-GlcNAc-modified protein.Increasing protein O-GlcNAcylation (through pharmacological inhibition of O-GlcNAcase) results in diminished Per2 protein levels, time-of-day-dependent induction of bmal1 gene expression, and phase advances in the suprachiasmatic nucleus clock. Collectively, these data suggest that the cardiomyocyte circadian clock increases protein O-GlcNAcylation in the heart during the active/ awake phase through coordinated regulation of the hexosamine biosynthetic pathway and that protein O-GlcNAcylation in turn influences the timing of the circadian clock.Circadian clocks have emerged as critical regulators of energy metabolism (1, 2). Animal models wherein components of these cell autonomous mechanisms are genetically manipulated invariably exhibit altered energy balance, resulting in overt metabolic phenotypes (e.g. obesity or leanness). This concept is exemplified when either Clock or Bmal1 (two transcription factors at the core of the mammalian clock) are disrupted; Clock⌬19 mutant mice are obesity-prone, whereas Bmal1 null mice are lean (3, 4). Appreciation for links between circadian clocks and metabolism has grown further through demonstration that perturbations in metabolism (e.g. changes in nutrient availability, models of obesity, and diabetes mellitus, etc.) in turn influence the clock mechanism (5-7). Collectively, these observations have fueled identification of a number of posttranslational mediators that facilitate the interdependence of circadian clocks with metabolism. These include phosphorylation, ubiquitination, acetylation, and ribosylation of critical clock and/or metabolic components in time-of-day-dependent manners (1, 8 -14).Defining the role of a specific cell autonomous circadian clock in metabolic regulation through the use of animal models wherein clock components are genetically altered in a ubiquitous fashion is often hampered by the fact that time-of-day-dependent rhythms are altered at multiple levels (e.g. behavioral, neurohum...

Administration of human recombinant erythropoietin (EPO) at time of acute ischemic renal injury (IRI) inhibits apoptosis, enhances tubular epithelial regeneration, and promotes renal functional recovery. The present study aimed to determine whether darbepoetin-alfa (DPO) exhibits comparable renoprotection to that afforded by EPO, whether pro or antiapoptotic Bcl-2 proteins are involved, and whether delayed administration of EPO or DPO 6 h following IRI ameliorates renal dysfunction. The model of IRI involved bilateral renal artery occlusion for 45 min in rats (N = 4 per group), followed by reperfusion for 1-7 days. Controls were sham-operated. Rats were treated at time of ischemia or sham operation (T0), or post-treated (6 h after the onset of reperfusion, T6) with EPO (5000 IU/kg), DPO (25 mug/kg), or appropriate vehicle by intraperitoneal injection. Renal function, structure, and immunohistochemistry for Bcl-2, Bcl-XL, and Bax were analyzed. DPO or EPO at T0 significantly abrogated renal dysfunction in IRI animals (serum creatinine for IRI 0.17 +/- 0.05 mmol/l vs DPO-IRI 0.08 +/- 0.03 mmol/l vs EPO-IRI 0.04 +/- 0.01 mmol/l, P = 0.01). Delayed administration of DPO or EPO (T6) also significantly abrogated subsequent renal dysfunction (serum creatinine for IRI 0.17 +/- 0.05 mmol/l vs DPO-IRI 0.06 +/- 0.01 mmol/l vs EPO-IRI 0.03 +/- 0.03 mmol/l, P = 0.01). There was also significantly decreased tissue injury (apoptosis, P < 0.05), decreased proapoptotic Bax, and increased regenerative capacity, especially in the outer stripe of the outer medulla, with DPO or EPO at T0 or T6. These results reaffirm the potential clinical application of DPO and EPO as novel renoprotective agents for patients at risk of ischemic acute renal failure or after having sustained an ischemic renal insult.

Promotion of tubular epithelial proliferation and survival, and interstitial cell apoptosis, may minimize renal fibrosis after UUO. In the present study, both were linked spatially and temporally with increased pERK expression. Fluvastatin treatment attenuated UUO-induced fibrosis via an antioxidant and pERK-related mechanism.

Background The volume overload of isolated mitral regurgitation (MR) in the dog results in left ventricular (LV) dilatation and interstitial collagen loss. To better understand the mechanism of collagen loss we performed a gene array and overlaid regulated genes into Ingenuity Pathway Analysis (IPA). Methods and Results Gene arrays from LV tissue were compared in 4 dogs prior to and 4 months after MR. Cine-magnetic resonance-derived LV end-diastolic volume increased 2-fold (p=0.005) and LV ejection fraction increased from 41 to 53% (p < 0.001). LV interstitial collagen decreased 40% (p<0.05) compared to controls and replacement collagen was in short strands and in disarray. IPA identified Marfan’s syndrome, aneurysm formation, LV dilatation, and myocardial infarction, all of which have extracellular matrix (ECM) protein defects and/or degradation. MMP-1 and -9 mRNA increased 5- (p=0.01) and 10-fold (0.003), while collagen I did not change and collagen III mRNA increased 1.5-fold (p=0.02). However, noncollagen genes important in ECM structure were significantly downregulated, including decorin, fibulin 1, and fibrillin 1. Decorin mRNA downregulation correlated with LV dilatation (r= 0.83 p<0.05). In addition, connective tissue growth factor and plasminogen activator inhibitor were downregulated, along with multiple genes in TGF-β signaling pathway, resulting decreased LV TGF-β1 activity (p=0.03). Conclusions LV collagen loss in isolated, compensated MR is chiefly due to post-translational processing and degradation. The downregulation of multiple noncollagen genes important in global ECM structure, coupled with decreased expression of multiple profibrotic factors, explain the failure to replace interstitial collagen in the MR heart.