Kim-1/Tim-1 and Immune Cells: Shifting Sands

Kim-1/Tim-1 is an apoptotic-cell phagocytosis and scavenger receptor that is most highly upregulated in proximal tubular epithelium in acute and chronic kidney injury. While Kim-1/Tim-1 has been proposed to be a costimulatory molecule for immune cells, its potential immunological role has been controversial. In the presence of very high epithelial cell expression understanding the influence of immune cell Kim-1/Tim-1 expression in kidney injury relies on a better definition of its functional significance in immune cells and better characterization of antibodies used to probe function

Targeted Proximal Tubule Injury Triggers Interstitial Fibrosis and Glomerulosclerosis

Chronic kidney disease (CKD) remains one of the leading causes of death in the developed world and acute kidney injury (AKI) is now recognized as a major risk factor in its development. Understanding the factors leading to CKD after acute injury are limited by current animal models of AKI which concurrently target various kidney cell types such as epithelial, endothelial and inflammatory cells. Here we developed a mouse model of kidney injury using the Six2-Cre-LoxP technology to selectively activate expression of the simian diphtheria toxin receptor in renal epithelia derived from the metanephric mesenchyme. By adjusting the timing and dose of diphtheria toxin a highly selective model of tubular injury was created to define the acute and chronic consequences of isolated epithelial injury. The diphtheria toxin-induced sublethal tubular epithelial injury was confined to the S1 and S2 segments of the proximal tubule rather than being widespread in the metanephric mesenchyme derived epithelial lineage. Acute injury was promptly followed by inflammatory cell infiltration and robust tubular cell proliferation leading to complete recovery after a single toxin insult. In striking contrast, three insults to renal epithelial cells at one week intervals resulted in maladaptive repair with interstitial capillary loss, fibrosis and glomerulosclerosis which was highly correlated with the degree of interstitial fibrosis. Thus, selective epithelial injury can drive the formation of interstitial fibrosis, capillary rarefaction and potentially glomerulosclerosis, substantiating a direct role for damaged tubule epithelium in the pathogenesis of CKD

Loss of leucine-rich repeat kinase 2 causes age-dependent bi-phasic alterations of the autophagy pathway

<p>Abstract</p> <p>Background</p> <p>Dominantly inherited missense mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common genetic cause of Parkinson's disease, but its normal physiological function remains unclear. We previously reported that loss of LRRK2 causes impairment of protein degradation pathways as well as increases of apoptotic cell death and inflammatory responses in the kidney of aged mice.</p> <p>Results</p> <p>Our analysis of <it>LRRK2</it>-/- kidneys at multiple ages, such as 1, 4, 7, and 20 months, revealed unique age-dependent development of a variety of molecular, cellular, and ultrastructural changes. Gross morphological abnormalities of the kidney, including altered size, weight, texture, and color, are evident in <it>LRRK2</it>-/- mice at 3-4 months of age, along with increased accumulation of autofluorescent granules in proximal renal tubules. The ratio of kidney/body weight in <it>LRRK2</it>-/- mice is increased at 1, 4, and 7 months of age (~10% at 1 month, and ~20% at 4 and 7 months), whereas the ratio is drastically decreased at 20 months of age (~50%). While kidney filtration function evaluated by levels of blood urea nitrogen and serum creatinine is not significantly affected in <it>LRRK2</it>-/- mice at 12-14 months of age, expression of kidney injury molecule-1, a sensitive and specific biomarker for epithelial cell injury of proximal renal tubules, is up-regulated (~10-fold). Surprisingly, loss of LRRK2 causes age-dependent bi-phasic alterations of the autophagic activity in <it>LRRK2</it>-/- kidneys, which is unchanged at 1 month of age, enhanced at 7 months but reduced at 20 months, as evidenced by corresponding changes in the levels of LC3-I/II, a reliable autophagy marker, and p62, an autophagy substrate. Levels of α-synuclein and protein carbonyls, a general oxidative damage marker, are also decreased in <it>LRRK2</it>-/- kidneys at 7 months of age but increased at 20 months. Interestingly, the age-dependent bi-phasic alterations in autophagic activity in <it>LRRK2</it>-/- kidneys is accompanied by increased levels of lysosomal proteins and proteases at 1, 7, and 20 months of age as well as progressive accumulation of autolysosomes and lipofuscin granules at 4, 7-10, and 20 months of age.</p> <p>Conclusions</p> <p>LRRK2 is important for the dynamic regulation of autophagy function <it>in vivo</it>.</p

Regulatory mechanisms of anthrax toxin receptor 1-dependent vascular and connective tissue homeostasis

It is well known that angiogenesis is linked to fibrotic processes in fibroproliferative diseases, but insights into pathophysiological processes are limited, due to lack of understanding of molecular mechanisms controlling endothelial and fibroblastic homeostasis. We demonstrate here that the matrix receptor anthrax toxin receptor 1 (ANTXR1), also known as tumor endothelial marker 8 (TEM8), is an essential component of these mechanisms. Loss of TEM8 function in mice causes reduced synthesis of endothelial basement membrane components and hyperproliferative and leaky blood vessels in skin. In addition, endothelial cell alterations in mutants are almost identical to those of endothelial cells in infantile hemangioma lesions, including activated VEGF receptor signaling in endothelial cells, increased expression of the downstream targets VEGF and CXCL12, and increased numbers of macrophages and mast cells. In contrast, loss of TEM8 in fibroblasts leads to increased rates of synthesis of fiber-forming collagens, resulting in progressive fibrosis in skin and other organs. Compromised interactions between TEM8-deficient endothelial and fibroblastic cells cause dramatic reduction in the activity of the matrix-degrading enzyme MMP2. In addition to insights into mechanisms of connective tissue homeostasis, our data provide molecular explanations for vascular and connective tissue abnormalities in GAPO syndrome, caused by loss-of-function mutations in ANTXR1. Furthermore, the loss of MMP2 activity suggests that fibrotic skin abnormalities in GAPO syndrome are, in part, the consequence of pathophysiological mechanisms underlying syndromes (NAO, Torg and Winchester) with multicentric skin nodulosis and osteolysis caused by homozygous loss-of-function mutations in MMP2

Ectopic high endothelial venules in pancreatic ductal adenocarcinoma: A unique site for targeted delivery.

BACKGROUND: Nanomedicine offers an excellent opportunity to tackle treatment-refractory malignancies by enhancing the delivery of therapeutics to the tumor site. High endothelial venules (HEVs) are found primarily in lymph nodes or formed de novo in peripheral tissues during inflammatory responses. They express peripheral node addressin (PNAd), which is recognized by the monoclonal antibody MECA79. METHODS: Here, we demonstrated that HEVs form de novo in human pancreatic ductal adenocarcinoma (PDAC). We engineered MECA79 coated nanoparticles (MECA79-NPs) that recognize these ectopic HEVs in PDAC. FINDINGS: The trafficking of MECA79-NPs following intravenous delivery to human PDAC implanted in a humanized mouse model was more robust than non-conjugated NPs. Treatment with MECA79-Taxol-NPs augmented the delivery of Paclitaxel (Taxol) to the tumor site and significantly reduced the tumor size. This effect was associated with a higher apoptosis rate of PDAC cells and reduced vascularization within the tumor. INTERPRETATION: Targeting the HEVs of PDAC using MECA79-NPs could lay the ground for the localized delivery of a wide variety of drugs including chemotherapeutic agents. FUND: National Institutes of Health (NIH) grants: T32-EB016652 (B·B.), NIH Cancer Core Grant CA034196 (L.D.S.), National Institute of Allergy and Infectious Diseases grants R01-AI126596 and R01-HL141815 (R.A.)

Targeted Delivery of Immunomodulators to Lymph Nodes

SUMMARY Active-targeted delivery to lymph nodes represents a major advance toward more effective treatment of immune-mediated disease. The MECA79 antibody recognizes peripheral node address in molecules expressed by high endothelial venules of lymph nodes. By mimicking lymphocyte trafficking to the lymph nodes, we have engineered MECA79-coated microparticles containing an immunosuppressive medication, tacrolimus. Following intravenous administration, MECA79-bearing particles showed marked accumulation in the draining lymph nodes of transplanted animals. Using an allograft heart transplant model, we show that targeted lymph node delivery of microparticles containing tacrolimus can prolong heart allograft survival with negligible changes in tacrolimus serum level. Using MECA79 conjugation, we have demonstrated targeted delivery of tacrolimus to the lymph nodes following systemic administration, with the capacity for immune modulation in vivo

Association of Coding Variants in Hydroxysteroid 17-beta Dehydrogenase 14 (HSD17B14) with Reduced Progression to End Stage Kidney Disease in Type 1 Diabetes

Background Rare variants ingenecodingregions likely have agreater impactondisease-relatedphenotypes than common variants through disruption of their encoded protein. We searched for rare variants associated with onset of ESKD in individuals with type 1 diabetes at advanced kidney disease stage. Methods Gene-basedexome array analyses of15,449genes infivelarge incidence cohortsof individualswith type 1diabetes andproteinuriawere analyzedfor survival time toESKD, testing the top gene in a sixth cohort (n52372/1115 events all cohorts) and replicating in two retrospective case-control studies (n51072 cases, 752 controls). Deep resequencing of the top associated gene in five cohorts confirmed the findings. We performed immunohistochemistry and gene expression experiments in human control and diseased cells, and in mouse ischemia reperfusion and aristolochic acid nephropathy models. Results Protein coding variants in the hydroxysteroid 17- b dehydrogenase 14 gene (HSD17B14), predicted to affect protein structure, had a net protective effect against development of ESKD at exome-wide significance (n54196; P value53.331027). The HSD17B14 gene and encoded enzyme were robustly expressed in healthy human kidney, maximally in proximal tubular cells. Paradoxically, gene and protein expression were attenuated in human diabetic proximal tubules and in mouse kidney injury models. Expressed HSD17B14 gene and protein levels remained low without recovery after 21 days in a murine ischemic reperfusion injury model. Decreased gene expression was found in other CKD-associated renal pathologies. Conclusions HSD17B14 gene ismechanistically involved in diabetic kidney disease. The encoded sex steroid enzyme is a druggable target, potentially opening a new avenue for therapeutic development.Peer reviewe

Urinary chemokine (C-C motif) ligand 2 (monocyte chemotactic protein-1) as a tubular injury marker for early detection of cisplatin-induced nephrotoxicity.

Because of the difficulty in detecting segment-specific response in the kidney, we investigated the molecular events underlying acute kidney injury in the proximal tubules of rats with cisplatin (cis-diamminedichloroplatinum II)-induced nephrotoxicity. Microarray analysis revealed that mRNA levels of several cytokines and chemokines, such as interleukin-1beta, chemokine (C-C motif) ligand (CCL) 2, CCL20, chemokine (C-X-C motif) ligand (CXCL) 1, and CXCL10 were significantly increased after cisplatin treatment in both isolated proximal tubules and whole kidney. Interestingly, tubular CCL2 mRNA levels increased soon after cisplatin administration, whereas CCL2 mRNA levels in whole kidney first decreased and then increased. Levels of both CCL2 and kidney injury molecule-1 (KIM-1) in the whole kidney increased after cisplatin administration. Immunofluorescence analysis revealed CCL2 changes in the proximal tubular cells initially and then in the medullary interstitium. Urinary CCL2 excretion significantly increased approximately 3-fold compared with controls the day after cisplatin administration (5mg/kg), when no changes were observed plasma creatinine and blood urea nitrogen levels. Urinary levels of KIM-1 also increased 3-fold after cisplatin administration. In addition, urinary CCL2 rather than KIM-1 increased in chronic renal failure rats after administration of low-dose cisplatin (2mg/kg), suggesting that urinary CCL2 was selective for cisplatin-induced nephrotoxicity in renal impairment. These results indicated that the increase in cytokine and chemokine expression in renal epithelial cells might be responsible for kidney deterioration in cisplatin-induced nephrotoxicity, and that urinary CCL2 is associated with tubular injury and serves as a sensitive and noninvasive marker for the early detection of cisplatin-induced tubular injury