Substance P chemokine interaction in Mouse Pancreatic Acinar cells, and its implications in acute pancreatitis

Ph.DDOCTOR OF PHILOSOPH

Adiponectin reduces glomerular endothelial glycocalyx disruption and restores glomerular barrier function in a mouse model of type 2 diabetes

Adiponectin has vascular anti-inflammatory and protective effects. Although adiponectin protects against the development of albuminuria, historically, the focus has been on podocyte protection within the glomerular filtration barrier (GFB). The first barrier to albumin in the GFB is the endothelial glycocalyx (eGlx), a surface gel-like barrier covering glomerular endothelial cells (GEnCs). In diabetes, eGlx dysfunction occurs before podocyte damage; hence, we hypothesized that adiponectin could protect from eGlx damage to prevent early vascular damage in diabetic kidney disease (DKD). Globular adiponectin (gAd) activated AMPK signaling in human GEnCs through AdipoR1. It significantly reduced eGlx shedding and the TNF-α–mediated increase in syndecan-4 (SDC4) and MMP2 mRNA expression in GEnCs in vitro. It protected against increased TNF-α mRNA expression in glomeruli isolated from db/db mice and against expression of genes associated with glycocalyx shedding (namely, SDC4, MMP2, and MMP9). In addition, gAd protected against increased glomerular albumin permeability (Ps’alb) in glomeruli isolated from db/db mice when administered intraperitoneally and when applied directly to glomeruli (ex vivo). Ps’alb was inversely correlated with eGlx depth in vivo. In summary, adiponectin restored eGlx depth, which was correlated with improved glomerular barrier function, in diabetes

Vascular endothelial growth factor-A165b is protective and restores endothelial glycocalyx in diabetic nephropathy

Diabetic nephropathy is the leading cause of ESRD in high-income countries and a growing problem across the world. Vascular endothelial growth factor-A (VEGF-A) is thought to be a critical mediator of vascular dysfunction in diabetic nephropathy, yet VEGF-A knockout and overexpression of angiogenic VEGF-A isoforms each worsen diabetic nephropathy. We examined the vasculoprotective effects of the VEGF-A isoform VEGF-A165b in diabetic nephropathy. Renal expression of VEGF-A165b mRNA was upregulated in diabetic individuals with well preserved kidney function, but not in those with progressive disease. Reproducing this VEGF-A165b upregulation in mouse podocytes in vivo prevented functional and histologic abnormalities in diabetic nephropathy. Biweekly systemic injections of recombinant human VEGF-A165b reduced features of diabetic nephropathy when initiated during early or advanced nephropathy in a model of type 1 diabetes and when initiated during early nephropathy in a model of type 2 diabetes. VEGF-A165b normalized glomerular permeability through phosphorylation of VEGF receptor 2 in glomerular endothelial cells, and reversed diabetes-induced damage to the glomerular endothelial glycocalyx. VEGF-A165b also improved the permeability function of isolated diabetic human glomeruli. These results show that VEGF-A165b acts via the endothelium to protect blood vessels and ameliorate diabetic nephropathy

A role for NPY-NPY2R signaling in albuminuric kidney disease

Albuminuria is an independent risk factor for the progression to end-stage kidney failure, cardiovascular morbidity, and premature death. As such, discovering signaling pathways that modulate albuminuria is desirable. Here, we studied the transcriptomes of podocytes, key cells in the prevention of albuminuria, under diabetic conditions. We found that Neuropeptide Y (NPY) was significantly down-regulated in insulin-resistant vs. insulin-sensitive mouse podocytes and in human glomeruli of patients with early and late-stage diabetic nephropathy, as well as other nondiabetic glomerular diseases. This contrasts with the increased plasma and urinary levels of NPY that are observed in such conditions. Studying NPY-knockout mice, we found that NPY deficiency in vivo surprisingly reduced the level of albuminuria and podocyte injury in models of both diabetic and nondiabetic kidney disease. In vitro, podocyte NPY signaling occurred via the NPY2 receptor (NPY2R), stimulating PI3K, MAPK, and NFAT activation. Additional unbiased proteomic analysis revealed that glomerular NPY-NPY2R signaling predicted nephrotoxicity, modulated RNA processing, and inhibited cell migration. Furthermore, pharmacologically inhibiting the NPY2R in vivo significantly reduced albuminuria in adriamycin-treated glomerulosclerotic mice. Our findings suggest a pathogenic role of excessive NPY-NPY2R signaling in the glomerulus and that inhibiting NPY-NPY2R signaling in albuminuric kidney disease has therapeutic potential. Chronic kidney disease (CKD) is a major global healthcare concern, affecting over 10% of the general population, and frequently occurs secondary to other systemic disorders including diabetes, obesity, hypertension, and the metabolic syndrome. A common early hallmark of CKD is albuminuria, which not only reflects damage to the glomerular filtration barrier (GFB) in the kidney but also is an important independent risk factor for the progression to end-stage renal failure and cardiovascular disease (1⇓–3). Thus, strategies to prevent albuminuria have important therapeutic potential, particularly in the early stages of CKD progression. Podocytes are highly specialized epithelial cells of the glomerulus, lining the urinary side of the filtration barrier. Owing to their complex, dynamic structures and their ability to secrete (and adapt to) a number of growth factors, these cells have a central role in filtration barrier maintenance (4). As such, podocyte damage is a key driver of albuminuria and glomerular disease in numerous settings and occurs early in the pathogenesis of many albuminuric conditions (5⇓⇓⇓–9). While it is well-established that podocyte damage is a major cause of albuminuria (8), the pathways and molecules involved in podocyte injury are incompletely understood. We (10, 11) and others (12, 13) have highlighted the importance of podocyte insulin responses in maintaining glomerular function, and it is now evident that circulating factors associated with common systemic disorders, including diabetes, obesity, and the metabolic syndrome, can directly induce podocyte insulin resistance (14⇓⇓–17) and associated damage (15, 18). In this study, we analyzed the transcriptomes of insulin-sensitive and insulin-resistant podocytes with the aim of identifying molecules that are differentially regulated in podocyte damage, which may play a role in albuminuric kidney disease. This unbiased transcriptome analysis revealed that Neuropeptide Y (Npy) was the most highly down-regulated transcript in insulin-resistant vs. insulin-sensitive podocytes. Analysis of patient cohorts also revealed a significant reduction in glomerular NPY expression in both early and late-stage diabetic nephropathy (DN), as well as in several other human albuminuric conditions. This contrasts with the increased plasma and urinary levels of NPY that are observed in diabetes and CKD (19⇓⇓–22). This prompted us to further investigate the potential role of NPY (and NPY signaling) in the podocyte and glomerulus