Vascular endothelial growth factor accelerates renal recovery in experimental thrombotic microangiopathy

Central role of podocytes in mediating cellular cross talk in glomerular health and disease

Podocytes are highly specialized epithelial cells that surround the capillaries of the glomeruli in the kidney. Together with the glomerular endothelial cells, these postmitotic cells are responsible for regulating filtrate from the circulating blood with their organized network of interdigitating foot processes that wrap around the glomerular basement membrane. Although podocyte injury and subsequent loss is the hallmark of many glomerular diseases, recent evidence suggests that the cell-cell communication between podocytes and other glomerular and nonglomerular cells is critical for the development and progression of kidney disease. In this review, we highlight these key cellular pathways of communication and how they might be a potential target for therapy in glomerular disease. We also postulate that podocytes might serve as a central hub for communication in the kidney under basal conditions and in response to cellular stress, which may have implications for the development and progression of glomerular diseases.

Chronic environmental hypoxia attenuates innate immunity activation and renal injury in two CKD models

Tissue hypoxia has been pointed out as a major pathogenic factor in chronic kidney disease (CKD). However, epidemiological and experimental evidence inconsistent with this notion has been described. We have previously reported that chronic exposure to low ambient Po2 promoted no renal injury in normal rats and in rats with 5/6 renal ablation (Nx) unexpectedly attenuated renal injury. In the present study, we investigated whether chronic exposure to low ambient Po2 would also be renoprotective in two additional models of CKD: adenine (ADE) excess and chronic nitric oxide (NO) inhibition. In both models, normobaric ambient hypoxia attenuated the development of renal injury and inflammation. In addition, renal hypoxia limited the activation of NF-κB and NOD-like receptor family pyrin domain containing 3 inflammasome cascades as well as oxidative stress and intrarenal infiltration by angiotensin II-positive cells. Renal activation of hypoxia-inducible factor (HIF)-2α, along with other adaptive mechanisms to hypoxia, may have contributed to these renoprotective effects. The present findings may contribute to unravel the pathogenesis of CKD and to the development of innovative strategies to arrest its progression.NEW & NOTEWORTHY Hypoxia is regarded as a major pathogenic factor in chronic kidney disease (CKD). In disagreement with this view, we show here that sustained exposure to low ambient Po2 lessened kidney injury and inflammation in two CKD models: adenine (ADE) excess and chronic nitric oxide (NO) inhibition. Together with our previous findings in the remnant kidney, these observations indicate that local changes elicited by hypoxia may exert renoprotection in CKD, raising the prospect of novel therapeutic strategies for this disease.

Mineralocorticoid Receptor Pathway Is a Key Mediator of Carfilzomib-induced Nephrotoxicity: Preventive Role of Eplerenone

Carfilzomib is an irreversible proteasome inhibitor indicated for relapsed/refractory multiple myeloma. Carfilzomib toxicity includes renal adverse effects (RAEs) of obscure pathobiology. Therefore, we investigated the mechanisms of nephrotoxicity developed by Carfilzomib. In a first experimental series, we used our previously established in vivo mouse models of Carfilzomib cardiotoxicity, that incorporated 2 and 4 doses of Carfilzomib, to identify whether Carfilzomib affects renal pathways. Hematology and biochemical analyses were performed, while kidneys underwent histological and molecular analyses. In a second and third experimental series, the 4 doses protocol was repeated for 24 hours urine collection and proteomic/metabolomic analyses. To test an experimental intervention, primary murine collecting duct tubular epithelial cells were treated with Carfilzomib and/or Eplerenone and Metformin. Finally, Eplerenone was orally co-administered with Carfilzomib daily (165 mg/kg) in the 4 doses protocol. We additionally used material from 7 patients to validate our findings and patients underwent biochemical analysis and assessment of renal mineralocorticoid receptor (MR) axis activation. In vivo screening showed that Carfilzomib-induced renal histological deficits and increased serum creatinine, urea, NGAL levels, and proteinuria only in the 4 doses protocol. Carfilzomib decreased diuresis, altered renal metabolism, and activated MR axis. This was consistent with the cytotoxicity found in primary murine collecting duct tubular epithelial cells, whereas Carfilzomib + Eplerenone co-administration abrogated Carfilzomib-related nephrotoxic effects in vitro and in vivo. Renal SGK-1, a marker of MR activation, increased in patients with Carfilzomib-related RAEs. Conclusively, Carfilzomib-induced renal MR/SGK-1 activation orchestrates RAEs and water retention both in vivo and in the clinical setting. MR blockade emerges as a potential therapeutic approach against Carfilzomib-related nephrotoxicity.

SENP1 protects cisplatin-induced AKI by attenuating apoptosis through regulation of HIF-1α

BACKGROUND

Acute kidney injury is a clinical syndrome with both high morbidity and mortality. However, the underlying molecular mechanism of AKI is still largely unknown. The role of SENP1 in AKI is unclear, while one of its substrates, HIF-1α possesses nephroprotective effect in AKI. Herein, this study aimed to reveal the role of SENP1/HIF-1α axis in AKI by using both cell and animal models.

METHODS

We investigated the effects of AKI on SENP1 expression using clinical samples, and cisplatin-induced AKI model based on mice or HK-2 cells. The influence of SENP1 knockdown or over-expression on cisplatin-induced AKI was studied in vitro and in vivo. Following the exploration of the change in HIF-1α expression brought by AKI, the synergistic effects of SENP1 knockdown and HIF-1α over-expression on AKI were examined.

RESULTS

The results showed the up-regulation of SENP1 in clinical specimens, as well as cell and animal models. The knockdown or over-expression of SENP1 in HK-2 cells could promote or inhibit AKI through regulating cell apoptosis, respectively. Moreover, SENP1^+/- mice suffered from much more serious AKI compared with mice in wild type group. Furthermore, we found that HIF-1α over-expression could attenuate the promoted cell apoptosis as well as AKI induced by SENP1 knockdown.

CONCLUSIONS

we showed that SENP1 provided protection for kidney in AKI via regulating cell apoptosis and through the regulation of HIF-1α. This study could benefit for the understanding of the pathogenesis of AKI and provide potential therapeutic target for AKI treatment.

Kidney-targeted irradiation triggers renal ischaemic preconditioning in mice

Renal ischemia/reperfusion (I/R) causes acute kidney injury (AKI). Ischemic preconditioning (IPC) attenuates I/R-associated AKI. Whole-body irradiation induces renal IPC in mice. Still, the mechanisms remain largely unknown. Furthermore, the impact of kidney-centered irradiation on renal resistance against I/R has not been studied. Renal irradiation (8.5Gy) was done in male 8-12-week-old C57bl/6 mice using Small Animal Radiation Therapy (SmART) device. Left renal I/R was performed by clamping the renal pedicles for 30 minutes, with simultaneous right nephrectomy, at 7, 14, and 28 days post-irradiation. The renal reperfusion lasted 48 hours. Following I/R, blood urea nitrogen (BUN) and creatinine (SCr) levels were lower in pre-irradiated mice compared to controls, so was the histological Jablonski score of AKI. The metabolomics signature of renal I/R was attenuated in pre-irradiated mice. The numbers of PCNA-, CD11b-, and F4-80-positive cells in the renal parenchyma post-I/R were reduced in pre-irradiated versus control groups. Such an IPC was significantly observed as early as D14 post-irradiation. RNA-Seq showed an up-regulation of angiogenesis- and stress response-related signaling pathways in irradiated non-ischemic kidneys at D28. RT-qPCR confirmed the increased expression of VEGF, ALK5, HO1, PECAM1, NOX2, HSP70, and HSP27 in irradiated kidneys compared to controls. In addition, irradiated kidneys showed an increased CD31-positive vascular area compared to controls. A 14-day gavage of irradiated mice with the anti-angiogenic drug Sunitinib before I/R abrogated the irradiation-induced IPC at both functional and structural levels. Our observations suggest that kidney-centered irradiation activates pro-angiogenic pathways and induces IPC, with preserved renal function and attenuated inflammation post-I/R.

Pro- and anti-fibrotic effects of vascular endothelial growth factor in chronic kidney diseases

Renal fibrosis is the inevitable common end-point of all progressive chronic kidney diseases. The underlying mechanisms of renal fibrosis are complex, and currently there is no effective therapy against renal fibrosis. Renal microvascular rarefaction contributes to the progression of renal fibrosis; however, an imbalance between proangiogenic and antiangiogenic factors leads to the loss of renal microvasculature. Vascular endothelial growth factor (VEGF) is the most important pro-angiogenic factor. Recent studies have unraveled the involvement of VEGF in the regulation of renal microvascular rarefaction and fibrosis via various mechanisms; however, it is not clear whether it has anti-fibrotic or pro-fibrotic effect. This paper reviews the available evidence pertaining to the function of VEGF in the fibrotic process and explores the associated underlying mechanisms. Our synthesis will help identify the future research priorities for developing specialized treatments for alleviating or preventing renal fibrosis. Abbreviation: VEGF: vascular endothelial growth factor; CKD: chronic kidney disease; ESKD: end-stage kidney disease; ER: endoplasmic reticulum; VEGFR: vascular endothelial growth factor receptor; AKI: acute kidney injury; EMT: epithelial-to-mesenchymal transition; HIF: hypoxia-inducible factor; α-SMA: α smooth muscle actin; UUO: unilateral ureteral obstruction; TGF-β: transforming growth factor-β; PMT: pericyte-myofibroblast transition; NO: nitric oxide; NOS: nitric oxide synthase; nNOS: neuronal nitric oxide synthase; iNOS: inducible nitric oxide synthase; eNOS: endothelial nitric oxide synthase; sGC: soluble guanylate cyclase; PKG: soluble guanylate cyclase dependent protein kinases; UP R: unfolded protein response

Comparison of the Surgical Resection and Infarct 5/6 Nephrectomy Rat Models of Chronic Kidney Disease

The 5/6 nephrectomy rat remnant kidney model is commonly employed to study chronic kidney disease (CKD). This model requires removal of one whole kidney and two-thirds of the other. The two most common ways of producing the remnant kidney are surgical resection of poles, known as the polectomy (Pol) model, or ligation of upper and lower renal arterial branches, resulting in pole infarction (Inf). These models have much in common, but also major phenotypic differences, and thus respectively model unique aspects of human CKD. The purpose of this review is to summarize phenotypic similarities and differences between these two models and their relation to human CKD, while emphasizing their vascular phenotype. In this article we review studies that have evaluated arterial blood pressure, the renin-angiotensin-aldosterone-system (RAAS), autoregulation, nitric oxide, single nephron physiology, angiogenic and anti-angiogenic factors, and capillary rarefaction in these two models. Phenotypic similarities: both models spontaneously develop hallmarks of human CKD including uremia, fibrosis, capillary rarefaction, and progressive renal function decline. They both undergo whole-organ hypertrophy, hyperfiltration of functional nephrons, reduced renal expression of angiogenic factor VEGF, increased renal expression of the anti-angiogenic thrombospondin-1, impaired renal autoregulation, and abnormal vascular nitric oxide physiology. Key phenotypic differences: the Inf model develops rapid-onset, moderate-to-severe systemic hypertension, and the Pol model early normotension followed by mild-to-moderate hypertension. The Inf rat has a markedly more active renin-angiotensin-aldosterone-system. Comparison of these two models facilitates understanding of how they can be utilized for studying CKD pathophysiology (e.g., RAAS dependent or independent pathology).

BECLIN1 Is Essential for Podocyte Secretory Pathways Mediating VEGF Secretion and Podocyte-Endothelial Crosstalk

Vascular endothelial growth factor A (VEGFA) secretion from podocytes is crucial for maintaining endothelial integrity within the glomerular filtration barrier. However, until now, the molecular mechanisms underlying podocyte secretory function remained unclear. Through podocyte-specific deletion of BECLIN1 (ATG6 or Becn1), a key protein in autophagy initiation, we identified a major role for this molecule in anterograde Golgi trafficking. The Becn1-deficient podocytes displayed aberrant vesicle formation in the trans-Golgi network (TGN), leading to dramatic vesicle accumulation and complex disrupted patterns of intracellular vesicle trafficking and membrane dynamics. Phenotypically, podocyte-specific deletion of Becn1 resulted in early-onset glomerulosclerosis, which rapidly progressed and dramatically reduced mouse life span. Further, in vivo and in vitro studies clearly showed that VEGFA secretion, and thereby endothelial integrity, greatly depended on BECLIN1 availability and function. Being the first to demonstrate the importance of a secretory pathway for podocyte integrity and function, we identified BECLIN1 as a key component in this complex cellular process. Functionally, by promoting VEGFA secretion, a specific secretory pathway emerged as an essential component for the podocyte-endothelial crosstalk that maintains the glomerular filtration barrier.

The endoplasmic reticulum stress and the unfolded protein response in kidney disease: Implications for vascular growth factors

Acute kidney injury (AKI) and chronic kidney disease (CKD) represent an important challenge for healthcare providers. The identification of new biomarkers/pharmacological targets for kidney disease is required for the development of more effective therapies. Several studies have shown the importance of the endoplasmic reticulum (ER) stress in the pathophysiology of AKI and CKD. ER is a cellular organelle devolved to protein biosynthesis and maturation, and cellular detoxification processes which are activated in response to an insult. This review aimed to dissect the cellular response to ER stress which manifests with activation of the unfolded protein response (UPR) with its major branches, namely PERK, IRE1α, ATF6 and the interplay between ER and mitochondria in the pathophysiology of kidney disease. Further, we will discuss the relationship between mediators of renal injury (with specific focus on vascular growth factors) and ER stress and UPR in the pathophysiology of both AKI and CKD with the aim to propose potential new targets for treatment for kidney disease.

Vascular mechanisms and molecular targets in hypertensive pregnancy and preeclampsia

Preeclampsia is a major complication of pregnancy manifested as hypertension and often intrauterine growth restriction, but the underlying pathophysiological mechanisms are unclear. Predisposing genetic and environmental factors cause placental maladaptations leading to defective placentation, apoptosis of invasive cytotrophoblasts, inadequate expansive remodeling of the spiral arteries, reduced uteroplacental perfusion pressure, and placental ischemia. Placental ischemia promotes the release of bioactive factors into the maternal circulation, causing an imbalance between antiangiogenic soluble fms-like tyrosine kinase-1 and soluble endoglin and proangiogenic vascular endothelial growth factor, placental growth factor, and transforming growth factor-β. Placental ischemia also stimulates the release of proinflammatory cytokines, hypoxia-inducible factor, reactive oxygen species, and angiotensin type 1 receptor agonistic autoantibodies. These circulating factors target the vascular endothelium, causing generalized endotheliosis in systemic, renal, cerebral, and hepatic vessels, leading to decreases in endothelium-derived vasodilators such as nitric oxide, prostacyclin, and hyperpolarization factor and increases in vasoconstrictors such as endothelin-1 and thromboxane A₂. The bioactive factors also target vascular smooth muscle and enhance the mechanisms of vascular contraction, including cytosolic Ca²⁺, protein kinase C, and Rho-kinase. The bioactive factors could also target matrix metalloproteinases and the extracellular matrix, causing inadequate vascular remodeling, increased arterial stiffening, and further increases in vascular resistance and hypertension. As therapeutic options are limited, understanding the underlying vascular mechanisms and molecular targets should help design new tools for the detection and management of hypertension in pregnancy and preeclampsia.

Astragaloside IV protects against diabetic nephropathy via activating eNOS in streptozotocin diabetes-induced rats

BACKGROUND

Astragaloside IV (AS-IV) was reported to play a role in improving diabetic nephropathy (DN), however, the underlying mechanisms still remain unclear. The aim of the present study is to investigate whether AS-IV ameliorates DN via the regulation of endothelial nitric oxide synthase (eNOS).

METHODS

DN model was induced in Sprague-Dawley (SD) male rats by intraperitoneal injection of 65 mg/kg streptozotocin (STZ). Rats in the AS-IV treatment group were orally gavaged with 5 mg/kg/day or 10 mg/kg/day AS-IV for eight consecutive weeks. Body weight, blood glucose, blood urea nitrogen (BUN), Serum creatinine (Scr), proteinuria and Glycosylated hemoglobin (HbA1c) levels were measured. Hematoxylin-Eosin (HE) and Periodic Acid-Schiff (PAS) staining were used to detect the renal pathology. The apoptosis status of glomerular cells was measured by TUNEL assay. The phosphorylation and acetylation of eNOS were detected by western blot. The effects of AS-IV on high-glucose (HG)-induced apoptosis and eNOS activity were also investigated in human renal glomerular endothelial cells (HRGECs) in vitro.

RESULTS

Treatment with AS-IV apparently reduced DN symptoms in diabetic rats, as evidenced by reduced BUN, Scr, proteinuria, HbA1c levels and expanding mesangial matrix. AS-IV treatment also promoted the synthesis of nitric oxide (NO) in serum and renal tissues and ameliorated the phosphorylation of eNOS at Ser 1177 with decreased eNOS acetylation. Moreover, HG-induced dysfunction of HRGECs including increased cell permeability and apoptosis, impaired eNOS phosphorylation at Ser 1177, and decreased NO production, were all reversed by AS-IV treatment.

CONCLUSIONS

These novel findings suggest that AS-IV ameliorates functional abnormalities of DN through inhibiting acetylation of eNOS and activating its phosphorylation at Ser 1177. AS-IV could be served as a potential therapeutic drug for DN.

TAFRO syndrome as a cause of glomerular microangiopathy: a case report and literature review

Background

TAFRO syndrome is a systemic inflammatory disorder that manifests as thrombocytopenia (T), anasarca (A), fever (F), reticulin fibrosis (R), and organomegaly (O). Renal dysfunction is frequently complicated with TAFRO syndrome, however, it is challenging to perform kidney biopsy in patients with TAFRO syndrome in the presence of thrombocytopenia. Renal histology in TAFRO syndrome mainly shows membranoproliferative glomerulonephritis (MPGN)-like lesions or thrombotic microangiopathy (TMA)-like glomerulopathy. We review our case and previous reports of TAFRO syndrome with kidney biopsy findings and discuss the renal pathophysiology of TAFRO syndrome.

Case presentation

We describe a previously healthy 48- year-old woman with TAFRO syndrome. Kidney biopsy performed before the treatment showed diffuse global endocapillary proliferative changes with endothelial cell swelling, double contours of partial capillary walls, and mesangiolysis, consistent with TMA-like glomerulopathy. Glucocorticoid therapy including steroid pulse was ineffective and she developed anasarca, renal dysfunction and oliguria. Hemodialysis was required. However, the anti-Interleukin (IL)-6 receptor antibody (tocilizumab) therapy was very effective. An increase in urinary volume was achieved about 2 weeks after the tocilizumab therapy and hemodialysis was discontinued. To investigate the renal pathophysiology of TAFRO syndrome, we performed immunohistological staining of vascular endothelial growth factor (VEGF)-A, CD34, and D2–40, in our case and a normal control kidney. Glomerular VEGF-A was especially positive in podocytes both, in the control and in the case, with no significant difference and there was a significant increase of VEGF-A staining area in the cortical peritubular capillaries in the case. Both glomerular and renal cortical CD34 expression were significantly decreased in our case. D2–40 expression in cortex was not significantly different.

Conclusions

We reviewed our case and other 10 previous reports about renal biopsy findings in TAFRO syndrome and found that glomerular microangiopathy was a common finding. IL-6-VEGF-axis-induced glomerular microangiopathy may play a crucial role in developing acute kidney injury in TAFRO syndrome and the anti-IL-6 receptor antibody therapy may be useful for TAFRO syndrome refractory to glucocorticoids. About the pathophysiology of VEGF in TAFRO syndrome, VEGF balance in the glomerulus and perhaps in the peritubular capillary system as well may be critical. Further investigation is needed.

PGC-1α, a potential therapeutic target against kidney aging

Aging is defined as changes in an organism over time. The proportion of the aged population is markedly increasing worldwide. The kidney, as an essential organ with a high energy requirement, is one of the most susceptible organs to aging. It is involved in glucose metabolism via gluconeogenesis, glucose filtration and reabsorption, and glucose utilization. Proximal tubular epithelial cells (PTECs) depend on lipid metabolism to meet the high demand for ATP. Recent studies have shown that aging‐related kidney dysfunction is highly associated with metabolic changes in the kidney. Peroxisome proliferator‐activated receptor gamma coactivator‐1 alpha (PGC‐1α), a transcriptional coactivator, plays a major role in the regulation of mitochondrial biogenesis, peroxisomal biogenesis, and glucose and lipid metabolism. PGC‐1α is abundant in tissues, including kidney PTECs, which demand high energy. Many in vitro and in vivo studies have demonstrated that the activation of PGC‐1α by genetic or pharmacological intervention prevents telomere shortening and aging‐related changes in the skeletal muscle, heart, and brain. The activation of PGC‐1α can also prevent kidney dysfunction in various kidney diseases. Therefore, a better understanding of the effect of PGC‐1α activation in various organs on aging and kidney diseases may unveil a potential therapeutic strategy against kidney aging.

Association of vascular endothelial growth factor and renal thrombotic microangiopathy-like lesions in patients with Castleman's disease

AIM

Renal thrombotic microangiopathy (TMA) is a common pathological manifestation of Castleman's disease (CD)-associated renal lesions. Increased level of plasma vascular endothelial growth factor (VEGF) has been shown in single-case reports. We aimed to investigate the dysregulation of VEGF in the pathogenesis of CD-associated TMA-like lesions (CD-TMA) in a larger cohort.

METHODS

Nineteen patients with clinico-pathologically diagnosed CD with renal involvement were enrolled. Ten patients with pregnancy TMA or TMA of unknown reasons were enrolled as TMA control group. The plasma levels of VEGF, soluble Flt-1 and interleukin-6 (IL-6) were detected using enzyme-linked immunosorbent assay kits. The expression of VEGF in the kidney biopsied tissue sections and the lymph node specimens were detected by immunostaining.

RESULTS

The plasma levels of VEGF and IL-6 levels were the highest in CD-TMA group compared to TMA control group and healthy controls. The levels of plasma VEGF was positively correlated with that of IL-6, and increased expression of VEGF and IL-6 was also observed in the lymph nodes from CD-TMA patients. However, the expression of VEGF in the glomerular podocytes was significantly decreased in CD-TMA group as well as in the TMA control.

CONCLUSION

Our findings suggest that renal VEGF expression might be important in the pathogenetic mechanism of CD-associated TMA-like lesions.

Continuous prospectively navigated multi-echo GRE for improved BOLD imaging of the kidneys

The objective of this study is to develop improved methods for renal blood oxygenation level dependent (BOLD) imaging. T2* mapping of the kidneys, or renal BOLD imaging, may depict renal oxygen levels and may be valuable as a noninvasive means of following the progression of renal disease. Current renal BOLD data is limited by imaging in a single breath hold, which results in low resolution and low signal-to-noise ratio (SNR). We compare a new free-breathing renal BOLD method with conventional breath-hold BOLD (BH-BOLD). A multi-echo GRE sequence with continuous prospective respiratory navigation and real-time feedback was developed that allows high resolution and high SNR renal BOLD imaging with constant sequence repetition time (TR) during free-breathing BOLD (FB-BOLD). The sequence was evaluated in 10 normal volunteers and compared with conventional BH-BOLD. Scan time for the FB-BOLD sequence was approximately three minutes, compared with 15 seconds for the BH-BOLD sequence. SNR of source images and residual error of T2* fitting were compared between the two methods. The FB-BOLD sequence produced motion-free T2* maps of the kidneys with SNR 1.9 times higher than BH-BOLD images. Residual error of T2* fitting was consistently lower in the right kidney with FB-BOLD (30% less than BH-BOLD) but higher in the left kidney (80% more than BH-BOLD), likely related to placement of the navigator on the right hemidiaphragm. A free-breathing prospectively navigated renal BOLD sequence allows flexible tradeoff between scan time, resolution, and SNR.

The associations of endothelial and podocyte injury in proliferative lupus nephritis: from observational analysis to in vitro study

Our study aims to evaluate the endothelial cell-podocyte crosstalk in proliferative lupus nephritis (LN). The semi-quantification scores of glomerular endothelial cell injury and the foot process width (FPW) were processed in 110 proliferative LN patients. Podocytes were stimulated with LN-derived IgG. Glomerular endothelial cells were treated with podocyte-conditioned medium (PCM), and then podocytes were incubated with endothelial cell-conditioned medium (ECM). The levels of vascular endothelial growth factor-A (VEGF-A) in PCM and endothelin-1 in ECM were analyzed, and the injury of podocyte and glomerular endothelial cells were further evaluated. The pathological score of glomerular endothelial cell injury was correlated with FPW in LN complicated with thrombotic microangiopathy. In vitro study showed the following: 1. Stimulation of podocytes by IgG from LN led to decline in the expression of nephrin with cytoskeleton rearrangement, and reduction of VEGF-A levels. 2. Exposure of glomerular endothelial cells to PCM incubated with LN-derived IgG (PCM-LN) induced more endothelin-1 secretion and disruption of intercellular tight junction. 3. Exposure of podocytes to ECM stimulated with PCM-LN could induce cytoskeleton redistribution with decrease of nephrin. In conclusion, the pathological glomerular endothelial cell lesions were associated with FPW and the VEGF-endothelin-1 system might play a critical role in the endothelial cell-podocyte crosstalk in LN.

Platelet-rich plasma ameliorates gamma radiation-induced nephrotoxicity via modulating oxidative stress and apoptosis

AIMS

As a source of growth factors and with its cytoprotective properties, platelet-rich plasma (PRP) received considerable attention in regenerative medicine. Thus, this study was designed to evaluate the protective efficacy of PRP against γ-radiation-induced nephrotoxicity.

MAIN METHODS

Forty male rats were distributed in four groups: 1) control, 2) PRP, 3) Radiation, and 4) PRP + radiation. Nephrotoxicity was examined in rats after a whole body γ-irradiation at a single dose of 8 Gy. Activated PRP (0.5 ml/kg BW) was injected subcutaneously twice weekly for three successive weeks prior to γ-irradiation. At the end of the experiment, creatinine, urea, albumin, and neutrophil gelatinase-associated lipocalin (NGAL) serum levels, as well as renal relative gene expression level of kidney injury molecule-1 (KIM-1) were estimated. Further, malondialdehyde level, nitric oxide content and reduced glutathione content in addition to superoxide dismutase and catalase activities were measured. Moreover, the expression levels of B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X (Bax), and caspase-3 proteins were assayed.

KEY FINDINGS

PRP pre-treatment significantly reduced the radiation-induced abnormalities in kidney histology and attenuated the induced cell injury. Furthermore, PRP notably ameliorated the state of oxidative stress and appeared to inhibit the induced apoptosis.

SIGNIFICANCE

This study lends a probable protective role of PRP against γ-radiation-induced nephrotoxicity which can highlight the possibilities of its application as a complementary procedure during radiotherapy.

Molecular determinants of microvascular dysfunction in hypertensive pregnancy and preeclampsia

Preeclampsia is a pregnancy-related disorder characterized by hypertension and often fetal intrauterine growth restriction, but the underlying mechanisms are unclear. Defective placentation and apoptosis of invasive cytotrophoblasts cause inadequate remodeling of spiral arteries, placental ischemia, and reduced uterine perfusion pressure (RUPP). RUPP causes imbalance between the anti-angiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin and the pro-angiogenic vascular endothelial growth factor and placental growth factor, and stimulates the release of proinflammatory cytokines, hypoxia-inducible factor, reactive oxygen species, and angiotensin AT1 receptor agonistic autoantibodies. These circulating factors target the vascular endothelium, smooth muscle and various components of the extracellular matrix. Generalized endotheliosis in systemic, renal, cerebral, and hepatic vessels causes decreases in endothelium-derived vasodilators such as nitric oxide, prostacyclin and hyperpolarization factor, and increases in vasoconstrictors such as endothelin-1 and thromboxane A2. Enhanced mechanisms of vascular smooth muscle contraction, such as intracellular Ca2+ , protein kinase C, and Rho-kinase cause further increases in vasoconstriction. Changes in matrix metalloproteinases and extracellular matrix cause inadequate vascular remodeling and increased arterial stiffening, leading to further increases in vascular resistance and hypertension. Therapeutic options are currently limited, but understanding the molecular determinants of microvascular dysfunction could help in the design of new approaches for the prediction and management of preeclampsia.

Matrix Metalloproteinases in Normal Pregnancy and Preeclampsia

Normal pregnancy is associated with marked hemodynamic and uterine changes that allow adequate uteroplacental blood flow and uterine expansion for the growing fetus. These pregnancy-associated changes involve significant uteroplacental and vascular remodeling. Matrix metalloproteinases (MMPs) are important regulators of vascular and uterine remodeling. Increases in MMP-2 and MMP-9 have been implicated in vasodilation, placentation, and uterine expansion during normal pregnancy. The increases in MMPs could be induced by the increased production of estrogen and progesterone during pregnancy. MMP expression/activity may be altered during complications of pregnancy. Decreased vascular MMP-2 and MMP-9 may lead to decreased vasodilation, increased vasoconstriction, hypertensive pregnancy, and preeclampsia. Abnormal expression of uteroplacental integrins, cytokines, and MMPs may lead to decreased maternal tolerance, apoptosis of invasive trophoblast cells, inadequate remodeling of spiral arteries, and reduced uterine perfusion pressure (RUPP). RUPP may cause imbalance between the antiangiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin and the proangiogenic vascular endothelial growth factor and placental growth factor, or stimulate the release of inflammatory cytokines, hypoxia-inducible factor, reactive oxygen species, and angiotensin AT1 receptor agonistic autoantibodies. These circulating factors could target MMPs in the extracellular matrix as well as endothelial and vascular smooth muscle cells, causing generalized vascular dysfunction, increased vasoconstriction and hypertension in pregnancy. MMP activity can also be altered by endogenous tissue inhibitors of metalloproteinases (TIMPs) and changes in the MMP/TIMP ratio. In addition to their vascular effects, decreases in expression/activity of MMP-2 and MMP-9 in the uterus could impede uterine growth and expansion and lead to premature labor. Understanding the role of MMPs in uteroplacental and vascular remodeling and function could help design new approaches for prediction and management of preeclampsia and premature labor.

A LASSO Method to Identify Protein Signature Predicting Post-transplant Renal Graft Survival

Identifying novel biomarkers to predict renal graft survival is important in post-transplant clinical practice. Serum creatinine, currently the most popular surrogate biomarker, offers limited information of the underlying allograft profiles. It is known to perform unsatisfactorily to predict renal function. In this paper, we apply a LASSO machine-learning algorithm in the Cox proportional hazards model to identify promising proteins that are associated with the hazard of allograft loss after renal transplantation, motivated by a clinical pilot study that collected 47 patients receiving renal transplants at the University of Michigan Hospital. We assess the association of 17 proteins previously identified by Cibrik et al. [5] with allograft rejection in our regularized Cox regression analysis, where the LASSO variable selection method is applied to select important proteins that predict the hazard of allograft loss. We also develop a post-selection inference to further investigate the statistical significance of the proteins on the hazard of allograft loss, and conclude that two proteins KIM-1 and VEGF-R2 are important protein markers for risk prediction.

Therapeutic angiogenesis by vascular endothelial growth factor supplementation for treatment of renal disease

PURPOSE OF REVIEW

Vascular endothelial growth factors (VEGFs) influence renal function through angiogenesis, with VEGF-A being the most potent inducer of vascular formation. In the normal glomerulus, tight homeostatic balance is maintained between the levels of VEGF-A isoforms produced by podocyte cells, and the VEGF receptors (VEGFRs) expressed by glomerular endothelial, mesangial, and podocyte cells. Renal disease occurs when this homeostatic balance is lost, manifesting in the abnormal autocrine and paracrine VEGF-A/VEGFR signaling, ultrastructural glomerular and tubular damage, and impaired filtration.

RECENT FINDINGS

Preclinical disease models of ischemic renal injury, including acute ischemia/reperfusion, thrombotic microangiopathy, and chronic renovascular disease, treated with exogenous VEGF supplementation demonstrated therapeutic efficacy. These results suggest a therapeutic VEGF-A paracrine effect on endothelial cells in the context of acute or chronic obstructive ischemia. Conversely, renal dysfunction in diabetic nephropathy appears to occur through an upregulated VEGF autocrine effect on podocyte cells, which is exacerbated by hyperglycemia. Therefore, VEGF supplementation therapy may be contraindicated for treatment of diabetic nephropathy, but specific results will depend on dose and on the specific site of VEGF delivery. A drug delivery system that demonstrates cell specificity for glomerular or peritubular capillaries could be employed to restore balance to VEGF-A/VEGFR2 signaling, and by doing so, prevent the progression to end-stage renal disease.

SUMMARY

The review discusses the preclinical data available for VEGF supplementation therapy in models of renal disease.

Effects of Platelet-Rich Plasma (PRP) on a Model of Renal Ischemia-Reperfusion in Rats

Renal ischemia-reperfusion injury is a major cause of acute renal failure, causing renal cell death, a permanent decrease of renal blood flow, organ dysfunction and chronic kidney disease. Platelet-rich plasma (PRP) is an autologous product rich in growth factors, and therefore able to promote tissue regeneration and angiogenesis. This product has proven its efficacy in multiple studies, but has not yet been tested on kidney tissue. The aim of this work is to evaluate whether the application of PRP to rat kidneys undergoing ischemia-reperfusion reduces mid-term kidney damage. A total of 30 monorrenal Sprague-Dawley male rats underwent renal ischemia-reperfusion for 45 minutes. During ischemia, PRP (PRP Group, n = 15) or saline solution (SALINE Group, n = 15) was administered by subcapsular renal injection. Control kidneys were the contralateral organs removed immediately before the start of ischemia in the remaining kidneys. Survival, body weight, renal blood flow on Doppler ultrasound, kidney weight, kidney volume, blood biochemistry and histopathology were determined for all subjects and kidneys, as applicable. Correlations between these variables were searched for. The PRP Group showed significantly worse kidney blood flow (p = 0.045) and more histopathological damage (p<0.0001). Correlations were found between body weight, kidney volume, kidney weight, renal blood flow, histology, and serum levels of creatinine and urea. Our study provides the first evidence that treatment with PRP results in the deterioration of the kidney’s response to ischemia-reperfusion injury.

Role of Receptor Tyrosine Kinase Signaling in Renal Fibrosis

Renal fibrosis can be induced in different renal diseases, but ultimately progresses to end stage renal disease. Although the pathophysiologic process of renal fibrosis have not been fully elucidated, it is characterized by glomerulosclerosis and/or tubular interstitial fibrosis, and is believed to be caused by the proliferation of renal inherent cells, including glomerular epithelial cells, mesangial cells, and endothelial cells, along with defective kidney repair, renal interstitial fibroblasts activation, and extracellular matrix deposition. Receptor tyrosine kinases (RTKs) regulate a variety of cell physiological processes, including metabolism, growth, differentiation, and survival. Many studies from in vitro and animal models have provided evidence that RTKs play important roles in the pathogenic process of renal fibrosis. It is also showed that tyrosine kinases inhibitors (TKIs) have anti-fibrotic effects in basic research and clinical trials. In this review, we summarize the evidence for involvement of specific RTKs in renal fibrosis process and the employment of TKIs as a therapeutic approach for renal fibrosis.

Mechanisms of Endothelial Dysfunction in Hypertensive Pregnancy and Preeclampsia

Preeclampsia is a pregnancy-related disorder characterized by hypertension and could lead to maternal and fetal morbidity and mortality. Although the causative factors and pathophysiological mechanisms are unclear, endothelial dysfunction is a major hallmark of preeclampsia. Clinical tests and experimental research have suggested that generalized endotheliosis in the systemic, renal, cerebral, and hepatic circulation could decrease endothelium-derived vasodilators such as nitric oxide, prostacyclin, and hyperpolarization factor and increase vasoconstrictors such as endothelin-1 and thromboxane A2, leading to increased vasoconstriction, hypertension, and other manifestation of preeclampsia. In search for the upstream mechanisms that could cause endothelial dysfunction, certain genetic, demographic, and environmental risk factors have been suggested to cause abnormal expression of uteroplacental integrins, cytokines, and matrix metalloproteinases, leading to decreased maternal tolerance, apoptosis of invasive trophoblast cells, inadequate spiral arteries remodeling, reduced uterine perfusion pressure (RUPP), and placental ischemia/hypoxia. RUPP may cause imbalance between the antiangiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin and the proangiogenic factors vascular endothelial growth factor and placental growth factor, or stimulate the release of other circulating bioactive factors such as inflammatory cytokines, hypoxia-inducible factor-1, reactive oxygen species, and angiotensin AT1 receptor agonistic autoantibodies. These circulating factors could then target endothelial cells and cause generalized endothelial dysfunction. Therapeutic options are currently limited, but understanding the factors involved in endothelial dysfunction could help design new approaches for prediction and management of preeclampsia.

The Vascular Endothelial Growth Factors-Expressing Character of Mesenchymal Stem Cells Plays a Positive Role in Treatment of Acute Lung Injury In Vivo

Recently, mesenchymal stem cells (MSC) have been proved to be beneficial in acute respiratory distress syndrome (ARDS). Vascular endothelial growth factor (VEGF) is an important angiogenesis factor that MSC release. However, the precise role of VEGF-expressing character of MSC in the MSC treatment for ARDS remains obscure. Here, we firstly knocked down the gene VEGF in MSC (MSC-ShVEGF) with lentiviral transduction. Then we injected the MSC-ShVEGF to rats with lipopolysaccharide-induced acute lung injury (ALI) via the tail vein. Data showed that MSC transplantation significantly increased VEGF levels in the lung, reduced lung permeability, protected lung endothelium from apoptosis, facilitated VE-cadherin recovery, controlled inflammation, and attenuated lung injury. However, VEGF gene knockdown in MSC led to relatively insufficient VEGF expression in the injured lung and significantly diminished the therapeutic effects of MSC on ALI, suggesting an important role of VEGF-expressing behavior of MSC in the maintenance of VEGF in the lung and the MSC treatment for ALI. Hence, we conclude that MSC restores the lung permeability and attenuates lung injury in rats with ALI in part by maintaining a “sufficient” VEGF level in the lung and the VEGF-expressing character of MSC plays a positive role in the therapeutic effects of MSC on ARDS.

Vascular growth factors play critical roles in kidney glomeruli

Kidney glomeruli ultrafilter blood to generate urine and they are dysfunctional in a variety of kidney diseases. There are two key vascular growth factor families implicated in glomerular biology and function, namely the vascular endothelial growth factors (VEGFs) and the angiopoietins (Angpt). We present examples showing not only how these molecules help generate and maintain healthy glomeruli but also how they drive disease when their expression is dysregulated. Finally, we review how manipulating VEGF and Angpt signalling may be used to treat glomerular disease.

Renal endothelial injury and microvascular dysfunction in acute kidney injury

The kidney is comprised of heterogeneous cell populations that function together to perform a number of tightly controlled, complex and interdependent processes. Renal endothelial cells contribute to vascular tone, regulation of blood flow to local tissue beds, modulation of coagulation and inflammation, and vascular permeability. Both ischemia and sepsis have profound effects on the renal endothelium, resulting in microvascular dysregulation resulting in continued ischemia and further injury. In recent years, the concept of the vascular endothelium as an organ that is both the source of and target for inflammatory injury has become widely appreciated. Here we revisit the renal endothelium in the light of ever evolving molecular advances.

Transactivation of EGFR by prostaglandin E2 receptors: a nuclear story?

The pharmacological modulation of hypoxia-inducible factor-1α (HIF-1α) and HIF-1α-regulated vascular endothelial growth factor-A (VEGF-A) in the kidney has therapeutic interest. Although it is assumed that prostaglandin E(2) (PGE(2)) exerts its biological effects from the extracellular medium through activation of EP receptors located at the cell membrane, we have shown in human renal proximal tubular HK-2 cells (and other cell lines) that intracellular PGE(2) regulates the expression of HIF-1α expression and the production of VEGF-A. Here, we have found--through experiments involving EP receptors agonists, EP receptor gene silencing and inhibition of the prostaglandin uptake transporter--that these biological effects of PGE(2) are mediated by intracellular EP(2) receptors. In sharp contrast with cell membrane EP(2), whose activation results in increased production of cAMP, intracellular EP(2) signaling was independent of cAMP. Instead, it involved c-src-dependent transactivation of epidermal growth factor receptor, which led to p38/ERK1/2-dependent activation of mitogen- and stress-activated kinase-1 (MSK-1) and to MSK-1-dependent-histone H3 phosphorylation and transcriptional up-regulation of retinoic acid receptor-β. Even more important, this signaling pathway was fully reproduced in nuclei isolated from HK-2 cell, which highlights the relevance of nuclear EP receptors in the up-regulation of HIF-1α. These results open the possibility that signal cascades that proceed entirely in the cell nucleus might be responsible for several PGE(2) effects that are assumed to be due to cell membrane EP receptors.

Platelets are relevant mediators of renal injury induced by primary endothelial lesions

Several studies have suggested a prominent (pro)inflammatory and harmful role of platelets in renal disease, and newer work has also demonstrated platelet release of proangiogenic factors. In the present study, we investigated the role of platelets in a mouse model of selective endothelial cell injury using either platelet depletion or the pharmacological P2Y12 receptor blocker clopidogrel as an interventional strategy. The concanavalin A/anti-concanavalin A model was induced in left kidneys of C57bl/6J wild-type mice after initial platelet depletion or platelet-inhibiting therapy using clopidogrel. FACS analysis of glycoprotein IIb/IIIa/P-selectin double-positive platelets and platelet-derived microparticles demonstrated relevant platelet activation after the induction of selective endothelial injury in mice. Enhanced platelet activation persisted for 5 days after disease induction and was accompanied by increased amounts of circulating platelet-derived microparticles as potential mediators of a prolonged procoagulant state. By immunohistochemistry, we detected significantly reduced glomerular injury in platelet-depleted mice compared with control mice. In parallel, we also saw reduced endothelial loss and a consequently reduced repair response as indicated by diminished proliferative activity. The P2Y12 receptor blocker clopidogrel demonstrated efficacy in limiting platelet activation and subsequent endothelial injury in this mouse model of renal microvascular injury. In conclusion, platelets are relevant mediators of renal injury induced by primary endothelial lesions early on, as demonstrated by platelet depletion as well as platelet inhibition via the P2Y12 receptor. While strategies to prevent platelet-endothelial interactions have shown protective effects, the contribution of platelets during renal regeneration remains unknown.

Role of Mesenchymal Stem Cells Transfected With Vascular Endothelial Growth Factor in Maintaining Renal Structure and Function in Rats with Unilateral Ureteral Obstruction

OBJECTIVES

Mesenchymal stem cells hold promise for renal disease treatment. Vascular endothelial growth factor may heal tubule-interstitial fibrosis in unilateral ureteral obstruction by inhibiting epithelial-mesenchymal transition. We investigated the protective effect of vascular endothelial growth factor in transfected mesenchymal stem cells in unilateral ureteral obstruction-induced renal injury in rats.

MATERIALS AND METHODS

Male Wistar Albino rats (32 rats; weight, 250-300 g) were divided into 4 equal groups: group 1, control; group 2, unilateral ureteral obstruction; group 3, unilateral ureteral obstruction and mesenchymal stem cells; and group 4, unilateral ureteral obstruction and vascular endothelial growth factor-transfected mesenchymal stem cells. Vascular endothelial growth factor-transfected mesenchymal stem cells were administered intravenously before onset of unilateral ureteral obstruction. On day 14, the rats were killed and kidneys were retrieved. Tubular necrosis, mononuclear cell infiltration, and interstitial fibrosis were evaluated in paraffin blocks. We evaluated green fluorescent protein-positive and vascular endothelial growth factor-positive cells; anti-inflammatory (Prostaglandin E2 receptor) and interleukin 1 receptor antagonist), proinflammatory/anti-inflammatory (interleukin 6), and proinflammatory (MPO) cytokine expression levels; and levels of nitric oxide; transforming growth factor β1, E-cadherin, and hydroxyproline.

RESULTS

Green fluorescent protein-positive cells were negative in the renal parenchyma in groups 1 and 2 and positive in groups 3 and 4. Vascular endothelial growth factor levels were significantly higher in group 4. Transforming growth factor β1, nitric oxide, and E-cadherin levels were significantly higher in the unilateral ureteral obstruction than control group; however, in the study groups, these values were not significantly different from the unilateral ureteral obstruction group. In stem cell-transplanted tissue samples, EP3, interleukin 1 receptor antagonist, and interleukin 6 levels were elevated, but MPO expression levels were low. Although there were significant differences for tubular necrosis and fibrosis in group 2, there were significant reductions in tubular injury and fibrosis in groups 3 and 4.

CONCLUSIONS

Systemic stem cells transplanted into the kidney protected against unilateral ureteral obstruction-induced renal epithelial-mesenchymal transition and renal fibrosis.

Tipping the balance from angiogenesis to fibrosis in CKD

Chronic progressive renal fibrosis leads to end-stage renal failure many patients with chronic kidney disease (CKD). Loss of the rich peritubular capillary network is a prominent feature, and seems independent of the specific underlying disease. The mechanisms that contribute to peritubular capillary regression include the loss of glomerular perfusion, as flow-dependent shear forces are required to provide the survival signal for endothelial cells. Also, reduced endothelial cell survival signals from sclerotic glomeruli and atrophic or injured tubule epithelial cells contribute to peritubular capillary regression. In response to direct tubular epithelial cell injury, and the inflammatory reaction that ensues, capillary pericytes dissociate from their blood vessels, also reducing endothelial cell survival. In addition, direct inflammatory injury of capillary endothelial cells, for instance in chronic allograft nephropathy, also contributes to capillary dropout. Chronic tissue hypoxia, which ensues from the rarefaction of the peritubular capillary network, can generate both an angiogenic and a fibrogenic response. However, in CKD, the balance is strongly tipped toward fibrogenesis. Understanding the underlying mechanisms for failed angiogenesis in CKD and harnessing endothelial-specific survival and pro-angiogenic mechanisms for therapy should be our goal if we are to reduce the disease burden from CKD.

Urinary and plasma levels of vasohibin-1 can predict renal functional deterioration in patients with renal disorders

Vasohibin-1 (VASH-1) is a negative feedback regulator of angiogenesis, and a small vasohibin-binding protein (SVBP) serves as its secretory chaperone and contributes to its antiangiogenic effects. In the present study, we aimed to define the clinical significance of VASH-1 and SVBP in patients with chronic kidney disease (CKD). We recruited 67 Japanese hospitalized patients with renal disorders with (n = 45) or without (n = 22) renal biopsy samples and 10 Japanese healthy controls. We evaluated the correlations between the plasma and urinary levels of VASH-1/VASH-1-SVBP complex/SVBP and the clinicopathological parameters. The plasma levels of VASH-1 were inversely correlated with age and systolic and diastolic blood pressure and positively correlated with crescent formation. Increased plasma and urinary levels of VASH-1 and VASH-1-SVBP complex were significantly correlated with worse renal outcomes. These results demonstrate an association between elevated urinary and plasma levels of VASH-1 and progressive decline of the renal function, thus suggesting a potential role for VASH-1 in predicting a worse renal prognosis in patients with renal disease, including CKD.

Prostaglandin E2 induces retinoic acid receptor-β up-regulation through MSK1

The pharmacological modulation of putative renoprotective factors hypoxia-inducible factor-1α (HIF-1α) and HIF-1α-regulated vascular endothelial growth factor-A (VEGF-A) in the kidney has therapeutic interest. In human renal proximal tubular HK2 cells, prostaglandin E2 (PGE2) up-regulates HIF-1α and VEGF-A through epidermal growth factor receptor (EGFR)-dependent up-regulation of retinoic acid receptor-β (RARβ). Here we studied the role of mitogen-activated protein kinases (MAPKs) ERK1/2 and p38 and their target kinase, mitogen- and stress activated kinase-1 (MSK1), in the signaling cascade. Treatment of HK2 cells with PGE2 resulted in increased phosphorylation of EGFR, the three studied kinases and the histone H3 (Ser10) at the RARβ gene promoter (the latter has been proposed as a molecular signature of the activated RARβ gene promoter). Prevention of the phosphorylation of EGFR, ERK1/2, p38 MAPK or MSK1 is by incubating, respectively, with AG1478, PD98059, SB203580 or H89 allowed to elucidate the precise phosphorylation order in the signaling cascade triggered by PGE2: first, EGFR; then, ERK1/2 and p38 MAPK and, finally, MSK1. Phosphorylation of MSK1 led to that of Ser10 in histone H3 and to activation of RARβ gene transcription (and the consequent increase in the expression of HIF-1α and VEGF-A), which was suppressed by H89 or by transfecting cells with a vector encoding for a dominant-negative mutant of MSK1. These results highlight the relevance of MSK1 in the up-regulation of RARβ by PGE2. They also may contribute to new therapeutic approaches based upon the pharmacological control of HIF-1α/VEGF-A in the proximal tubule through the modulation of the PGE2/EGFR/MAPK/MSK1/RARβ pathway.

Microparticles released by vascular endothelial cells increase hypoxia inducible factor expression in human proximal tubular HK-2 cells

Microparticles are produced by vesiculation of the cell plasma membrane and serve as vectors of cell-to-cell communication. Co-culture experiments have shown that hypoxia-inducible factor-α (HIF-α)-regulated-genes are up-regulated in human renal proximal tubular HK-2 cells by endothelial cell factors which might be transported inside endothelial microparticles (EMP). Here we aimed to study in HK-2 cells the effect of EMP, produced by activated endothelial cells, on HIF-α and HIF-α-regulated vascular endothelial growth factor-A (VEGF-A). EMP, at a concentration much lower than that found in plasma, increased the expression of HIF-α/VEGF-A in a COX-2/EP2 receptor dependent manner. Since the EMP/cells ratio was ∼1/1000, we hypothesized that paracrine mediators produced by HK-2 cells amplified the initial signal. This hypothesis was confirmed by two facts which also suggested that the mediators were conveyed by particles released by HK-2 cells: (i) HIF-α was up-regulated in HK-2 cells treated with the pellet obtained from the conditioned medium of the EMP-treated HK-2 cells. (ii) In transwell experiments, EMP-treated cells increased the expression of HIF-α in untreated HK-2 cells. Interestingly, we detected these cells, particles that were released by EMP-treated HK-2 cells. Depending on the pathological context, activation of HIF-α and VEGF-A signaling in renal tissue/cells may have either beneficial or harmful effects. Therefore, our results suggest that their presence in the urinary space of EMP produced by activated endothelial cells may influence the outcome of a number of renal diseases.

Antiangiogenic treatment diminishes renal injury and dysfunction via regulation of local AKT in early experimental diabetes

In view of increased vascular endothelial growth factor-A (VEGF-A) expression and renal dysfunction in early diabetes, we designed a study to test whether VEGF-A inhibition can prevent early renal injury and dysfunction. We investigated the relationship and mechanism between VEGF-A and AKT regulation. Invitro, VEGF-A small interfering RNA (siRNA) and AKT inhibitor MK-2206 were employed to podocytes and NRK-52 cells cultured in high glucose (30 mM). Invivo, the antiangiogenic drug endostatin was administered in 12 week-old streptozotocin-induced male Sprague Dawley rats. The levels of VEGF-A, AKT, phosphorylated Ser⁴⁷³-AKT, phosphorylated Thr³⁰⁸-AKT, nephrin, angiotensin II (Ang II), angiotensin type II receptor 1 (ATR1) were examined using quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR), Western blot analysis and immunohistochemistry. Interactions between phosphorylated Thr³⁰⁸-AKT and either nephrin in podocytes or Ang II in renal tubules were studied, respectively, using confocal immunofluorescence microscopy and immunoprecipitation. Silencing VEGF-A in podocytes upregulated phosphorylated Thr³⁰⁸-AKT and nephrin. Silencing VEGF-A in NRK-52E cells upregulated phosphorylated Thr³⁰⁸-AKT while downregulated Ang II and ATR1. MK-2206 enhanced VEGF-A expression in both podocytes and NRK-52E cells by inhibiting AKT activities. In diabetic rat kidneys, VEGF-A was upregulated and phosphorylated Thr³⁰⁸-AKT colocalized with either nephrin in podocytes or Ang II in renal tubules. With the endostatin treatment, the level of VEGF-A decreased while phosphorylated Thr³⁰⁸-AKT increased in both glomeruli and renal tubules. Treatment with endostatin upregulated nephrin in podocytes while downregulated Ang II and AT1R in renal tubules. Glomerular mesangial expansion was attenuated by the endostatin treatment, however, differences did not reach statistical significance. Endostatin ameliorated the interstitial fibrosis, urine albumin excretion rate (UAER) and albumin to creatinine ratio. We conclude that phosphorylated Thr³⁰⁸-AKT regulates VEGF-A expression by interacting with either nephrin in glomeruli or Ang II in renal tubules. Antiangiogenic treatment improves renal injury and function in early experimental diabetes.

Vascular endothelial growth factor-receptor 1 inhibition aggravates diabetic nephropathy through eNOS signaling pathway in db/db mice

The manipulation of vascular endothelial growth factor (VEGF)-receptors (VEGFRs) in diabetic nephropathy is as controversial as issue as ever. It is known to be VEGF-A and VEGFR2 that regulate most of the cellular actions of VEGF in experimental diabetic nephropathy. On the other hand, such factors as VEGF-A, -B and placenta growth factor bind to VEGFR1 with high affinity. Such notion instigated us to investigate on whether selective VEGFR1 inhibition with GNQWFI hexamer aggravates the progression of diabetic nephropathy in db/db mice. While diabetes suppressed VEGFR1, it did increase VEGFR2 expressions in the glomerulus. Db/db mice with VEGFR1 inhibition showed more prominent features with respect to, albuminuria, mesangial matrix expansion, inflammatory cell infiltration and greater numbers of apoptotic cells in the glomerulus, and oxidative stress than that of control db/db mice. All these changes were related to the suppression of diabetes-induced increases in PI3K activity and Akt phosphorylation as well as the aggravation of endothelial dysfunction associated with the inactivation of FoxO3a and eNOS-NOx. In cultured human glomerular endothelial cells (HGECs), high-glucose media with VEGFR1 inhibition induced more apoptotic cells and oxidative stress than did high-glucose media alone, which were associated with the suppression of PI3K-Akt phosphorylation, independently of the activation of AMP-activated protein kinase, and inactivation of FoxO3a and eNOS-NOx pathway. In addition, transfection with VEGFR1 siRNA in HGECs also suppressed PI3K-Akt-eNOS signaling. In conclusion, the specific blockade of VEGFR1 with GNQWFI caused severe renal injury related to profound suppression of the PI3K-Akt, FoxO3a and eNOS-NOx pathway, giving rise to the oxidative stress-induced apoptosis of glomerular cells in type 2 diabetic nephropathy.

SDF-1/CXCR4 signaling preserves microvascular integrity and renal function in chronic kidney disease

The progressive decline of renal function in chronic kidney disease (CKD) is characterized by both disruption of the microvascular architecture and the accumulation of fibrotic matrix. One angiogenic pathway recently identified as playing an essential role in renal vascular development is the stromal cell-derived factor-1α (SDF-1)/CXCR4 pathway. Because similar developmental processes may be recapitulated in the disease setting, we hypothesized that the SDF-1/CXCR4 system would regulate microvascular health in CKD. Expression of CXCR4 was observed to be increased in the kidneys of subtotally nephrectomized (SNx) rats and in biopsies from patients with secondary focal segmental glomerulosclerosis (FSGS), a rodent model and human correlate both characterized by aberration of the renal microvessels. A reno-protective role for local SDF-1/CXCR4 signaling was indicated by i) CXCR4-dependent glomerular eNOS activation following acute SDF-1 administration; and ii) acceleration of renal function decline, capillary loss and fibrosis in SNx rats treated with chronic CXCR4 blockade. In contrast to the upregulation of CXCR4, SDF-1 transcript levels were decreased in SNx rat kidneys as well as in renal fibroblasts exposed to the pro-fibrotic cytokine transforming growth factor β (TGF-β), the latter effect being attenuated by histone deacetylase inhibition. Increased renal SDF-1 expression was, however, observed following the treatment of SNx rats with the ACE inhibitor, perindopril. Collectively, these observations indicate that local SDF-1/CXCR4 signaling functions to preserve microvascular integrity and prevent renal fibrosis. Augmentation of this pathway, either purposefully or serendipitously with either novel or existing therapies, may attenuate renal decline in CKD.

Epidermal growth factor receptor transactivation by intracellular prostaglandin E2-activated prostaglandin E2 receptors. Role in retinoic acid receptor-β up-regulation

The pharmacological modulation of renoprotective factor vascular endothelial growth factor-A (VEGF-A) in the proximal tubule has therapeutic interest. In human proximal tubular HK-2 cells, treatment with all-trans retinoic acid or prostaglandin E2 (PGE2) triggers the production of VEGF-A. The pathway involves an initial increase in intracellular PGE2, followed by activation of EP receptors (PGE2 receptors, most likely an intracellular subset) and increase in retinoic acid receptor-β (RARβ) expression. RARβ then up-regulates transcription factor hypoxia-inducible factor-1α (HIF-1α), which increases the transcription and production of VEGF-A. Here we studied the role in this pathway of epidermal growth factor receptor (EGFR) transactivation by EP receptors. We found that EGFR inhibitor AG1478 prevented the increase in VEGF-A production induced by PGE2- and all-trans retinoic acid. This effect was due to the inhibition of the transcriptional up-regulation of RARβ, which resulted in loss of the RARβ-dependent transcriptional up-regulation of HIF-1α. PGE2 and all-trans retinoic acid also increased EGFR phosphorylation and this effect was sensitive to antagonists of EP receptors. The role of intracellular PGE2 was indicated by two facts; i) PGE2-induced EGFR phosphorylation was substantially prevented by inhibitor of prostaglandin uptake transporter bromocresol green and ii) all-trans retinoic acid treatment, which enhanced intracellular but not extracellular PGE2, had lower effect on EGFR phosphorylation upon pre-treatment with cyclooxygenase inhibitor diclofenac. Thus, EGFR transactivation by intracellular PGE2-activated EP receptors results in the sequential activation of RARβ and HIF-1α leading to increased production of VEGF-A and it may be a target for the therapeutic modulation of HIF-1α/VEGF-A.

VEGF suppresses epithelial-mesenchymal transition by inhibiting the expression of Smad3 and miR‑192, a Smad3-dependent microRNA

Transforming growth factor-β1 (TGF-β1)‑induced epithelial‑mesenchymal transition (EMT) is one of the important cellular and molecular mechanisms involved in renal fibrosis. Smad3 and miR-192 (a Smad3-dependent microRNA) are involved in TGF-β1-mediated EMT. Vascular endothelial growth factor (VEGF) is a renal tubular epithelial survival factor. Therefore, in the present study, we investigated the role of Smad3 and miR‑192 in the effects of VEGF on TGF‑β1‑mediated tubular EMT. A human kidney cortex (HKC) cell line stably overexpressing VEGF (HKC-SOEV) was established. The normal HKC cells and HKC‑SOEV cells were treated with TGF-β1 (5 µg/l) or/and LY294002 (20 µmol/l) for 24 and 48 h (LY294002 blocks the effect of VEGF). The protein expression of Smad2, Smad3, Smad4 and phosphorylated Smad3 (p‑Smad3) were measured by western blot analysis. The expression of Smad3 and miR-192 was determined by real‑time PCR. E-cadherin and α-smooth muscle actin (α-SMA) expression was detected by western blot analysis and laser scanning confocal microscopy (LSCM). TGF-β1 was found to induce the expression of α-SMA in the HKC cells. TGF-β1 also induced Smad3, miR-192 and p-Smad3 expression, but suppressed E‑cadherin expression. However, in the HKC-SOEV cells, the expression levels of α-SMA, Smad3, miR-192 and p‑Smad3 upon TGF-β1 stimulation were significantly reduced. In these cells, the suppressive effect of TGF-β1 on E‑cadherin was also reduced. Importantly, treatment with LY294002 significantly diminished the effect of VEGF. VEGF suppressed Smad3 and miR‑192, and subsequently inhibited EMT induced by TGF-β1.

Angiogenic cytokines in renovascular disease: do they have potential for therapeutic use?

Experimental and clinical studies suggest that the damage of the renal microvascular function and architecture may participate in the early steps of renal injury in chronic renal disease, irrespective of the cause. This supporting evidence has provided the impetus to targeting the renal microvasculature as an attempt to interfere with the progressive nature of the disease process. Chronic renovascular disease is often associated with renal microvascular dysfunction, damage, loss, and defective renal angiogenesis associated with progressive renal dysfunction and damage. It is possible that damage of the renal microvasculature in renovascular disease constitutes an initiating event for renal injury and contributes towards progressive and later on irreversible renal injury. Recent studies have suggested that protection of the renal microcirculation can slow or halt the progression of renal injury in this disease. This brief review will focus on the therapeutic potential and feasibility of using angiogenic cytokines to protect the kidney microvasculature in chronic renovascular disease. There is limited but provocative evidence showing that stimulation of vascular proliferation and repair using vascular endothelial growth factor or hepatocyte growth factor can slow the progression of renal damage, stabilize renal function, and protect the renal parenchyma. Such interventions may potentially constitute a sole strategy to preserve renal function and/or a co-adjuvant tool to improve the success of current therapeutic approaches in renovascular disease.

Clinical features and outcome of patients with HIV-negative multicentric Castleman's disease treated with combination chemotherapy: a report on 10 patients

To investigate the clinical characteristics and outcome of patients with HIV-negative multicentric Castleman's disease (MCD) treated exclusively with combination chemotherapy, and review literature to improve the diagnosis and management of this disease. A retrospective study was performed on the medical records of 10 patients with HIV-negative MCD treated exclusively with combination chemotherapy at one medical institution from May 2004 to April 2012. And relevant clinical, pathological, radiographic, and laboratory data were examined in order to evaluate treatment responses, with symptom onsets and survival period serving as the endpoints of the assessment. All patients have multifocal lymphadenopathy, and the associated system symptoms are found in 80 % of the cases. All patients were treated with lymphoma-based chemotherapy alone. The duration of follow-up ranged from 5 to 77 months for nine patients. Four patients were treated with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) alone: One was alive with no evidence of disease, and three were alive with disease. Three patients received cyclophosphamide, vincristine, and prednisone (COP) alone: One remained alive with disease, and two experienced recurrences and passed away. Two had only minimal response to COP and were switched to CHOP, and they were still alive with disease. MCD is a more progressive clinical entity, and long-term follow-up is necessary. CHOP chemotherapy may be an effective treatment option for patients with MCD, whereas when to start chemotherapy, how many cycles of chemotherapy required, and the role of combined radiotherapy remain to be further studied.

Netrin-1 attenuates the progression of renal dysfunction by inhibiting peritubular capillary loss and hypoxia in 5/6 nephrectomized rats

BACKGROUND/AIMS

The aim of this study was to investigate the effect of netrin-1 on peritubular capillary (PTC) loss and hypoxia in 5/6 nephrectomized (Nx) rats.

METHODS

Male Sprague-Dawley rats were divided into three groups (n = 10 rats/group): sham-operated rats treated with control adenovirus; 5/6 Nx rats treated with control adenovirus; and 5/6 Nx rats treated with recombinant adenovirus mediated netrin-1 gene (Ad-netrin-1) therapy. Rats were killed 12 weeks after surgery. Blood urea nitrogen (BUN), serum creatinine (Scr) and 24-h urinary albumin excretion rates were measured. Pathological changes in renal tissues were analyzed histologically. The concentration of netrin-1, CD34, and hypoxia-inducible factor-1α (HIF-1α) were analyzed by immunohistochemistry, Western blotting and real-time PCR.

RESULTS

Renal function and histopathological damage were significantly improved in Adnetrin-1 treated 5/6 Nx rats, compared with rats treated with the control adenovirus in the 5/6 Nx group. Furthermore, Ad-netrin-1 treatment induced a significant increase in renal PTC density, accompanied by a significant decrease in HIF-1α expression.

CONCLUSION

Adenovirus mediated netrin-1 treatment attenuates PTC damage, relieves tissues hypoxia and improves renal function, thus alleviating renal pathological changes and interstitial fibrosis in 5/6 Nx rats.

The endothelium in diabetic nephropathy

The long-term complications of diabetes are characterized by pathologic changes in both the microvasculature and conduit vessels. Although the fenestrated glomerular endothelium classically has been viewed as providing little in the way of an impediment to macromolecular flow, increasing evidence illustrates that this is not the case. Rather, hyperglycemia-mediated endothelial injury may predispose to albuminuria in diabetes both through direct effects and through bidirectional communication with neighboring podocytes. Although neo-angiogenesis of the glomerular capillaries may be a feature of early diabetes, particularly in the experimental setting, loss of capillaries in the glomerulus and in the interstitium are key events that each correlate closely with declining glomerular filtration rate in patients with diabetic nephropathy. The hypoxic milieu that follows the microvascular rarefaction provides a potent stimulus for fibrogenesis, leading to the glomerulosclerosis and tubulointerstitial fibrosis that characterize advanced diabetic kidney disease. Given the pivotal role the endothelium plays in both the development and the progression of diabetic nephropathy we need effective strategies that prevent its loss or accelerate its regeneration. Such advances likely will lead not only to improved tissue oxygenation and reduced fibrosis, but also to improved long-term renal function.

Mesenchymal stem cell therapy promotes renal repair by limiting glomerular podocyte and progenitor cell dysfunction in adriamycin-induced nephropathy

We previously reported that in a model of spontaneously progressive glomerular injury with early podocyte loss, abnormal migration, and proliferation of glomerular parietal epithelial progenitor cells contributed to the formation of synechiae and crescentic lesions. Here we first investigated whether a similar sequence of events could be extended to rats with adriamycin (ADR)-induced nephropathy. As a second aim, the regenerative potential of therapy with bone marrow-derived mesenchymal stem cells (MSCs) on glomerular resident cells was evaluated. In ADR-treated rats, decrease of WT1(+) podocyte number due to apoptosis was associated with reduced glomerular expression of nephrin and CD2AP. As a consequence of podocyte injury, glomerular adhesions of the capillary tuft to the Bowman's capsule were observed, followed by crescent-like lesions and glomerulosclerosis. Cellular components of synechiae were either NCAM(+) parietal progenitor cells or nestin(+) podocytes. In ADR rats, repeated injections of MSCs limited podocyte loss and apoptosis and partially preserved nephrin and CD2AP. MSCs attenuated the formation of glomerular podocyte-parietal epithelial cell bridges and normalized the distribution of NCAM(+) progenitor cells along the Bowman's capsule, thereby reducing glomerulosclerosis. Finding that MSCs increased glomerular VEGF expression and limited microvascular rarefaction may explain the prosurvival effect by stem cell therapy. MSCs also displayed anti-inflammatory activity. Coculture of MSCs with ADR-damaged podocytes showed a functional role of stem cell-derived VEGF on prosurvival pathways. These data suggest that MSCs by virtue of their tropism for damaged kidney and ability to provide a local prosurvival environment may represent a useful strategy to preserve podocyte viability and reduce glomerular inflammation and sclerosis.

Intracrine prostaglandin E(2) signalling regulates hypoxia-inducible factor-1α expression through retinoic acid receptor-β

We have previously found in human renal proximal tubular HK-2 cells that hypoxia- and all-trans retinoic acid-induced hypoxia-inducible factor-1α up-regulation is accompanied by retinoic acid receptor-β up-regulation. Here we first investigated whether hypoxia-inducible factor-1α expression is dependent on retinoic acid receptor-β and our results confirmed it since (i) hypoxia-inducible factor-1α-inducing agents hypoxia, hypoxia-mimetic agent desferrioxamine, all-trans retinoic acid and interleukin-1β increased retinoic acid receptor-β expression, (ii) hypoxia-inducible factor-1α up-regulation was prevented by retinoic acid receptor-β antagonist LE-135 or siRNA retinoic acid receptor-β and (iii) there was direct binding of retinoic acid receptor-β to the retinoic acid response element in hypoxia-inducible factor-1α promoter upon treatment with all-trans retinoic acid and 16,16-dimethyl-prostaglandin E(2). Since intracellular prostaglandin E(2) mediates hypoxia-inducible factor-1α up-regulation in normoxia in HK-2 cells, we next investigated and confirmed, its role in the up-regulation of retinoic acid receptor-β in normoxia by hypoxia-inducible factor-1α-inducing agents all-trans retinoic acid, interleukin-1β and 16,16-dimethyl-prostaglandin E(2) by inhibiting cyclooxygenases, prostaglandin influx transporter or EP receptors. Interestingly, the hypoxia-induced increase in retinoic acid receptor-β expression and accumulation of hypoxia-inducible factor-1α was also blocked by the inhibitors tested. This is the first time, to our knowledge, that retinoic acid receptor-β signalling is involved in the control of the expression of transcription factor hypoxia-inducible factor-1α in both normoxia and hypoxia and that retinoic acid receptor-β expression is found to be strictly regulated by intracellular prostaglandin E(2). Given the relevance of hypoxia-inducible factor-1α in the kidney in terms of tumorigenesis, progressive renal failure, production of erythropoietin and protection in several models of renal disease, our results open new therapeutic opportunities on the control of hypoxia-inducible factor-1α based upon the pharmacological modulation of retinoic acid receptor-β, either directly or through the control of intracellular prostaglandin E(2) levels/signalling.

Platelets are not critical effector cells for the time course of murine passive crescentic glomerulonephritis

Although platelets are well-known effector cells of inflammatory renal disease, clinical studies were not able to establish platelet inhibition as an effective therapy. Our previous studies using Vasodilator stimulated Phosphoprotein- and P2Y1-deficient mice suggested some early, but no long-term effects of platelets in passive crescentic glomerulonephritis. To define the role of platelets for this disease model, passive crescentic glomerulonephritis was induced in 72 C57Bl/6 mice by intraperitoneal injection of sheep anti-rabbit glomerular basement membrane antibody on 2 consecutive days. Platelets were depleted using anti-glycoprotein Ibα antibodies (p0p3/p0p4) every 4th day. Mice treated with equal amounts of sterile Phosphate buffered solution or rat-IgG served as controls. Blood, urine, and tissues were harvested on days 3 and 28. Renal tissue sections were evaluated after immunostaining using (semi)quantitative and computer-assisted image analysis. Compared to controls, efficient depletion was achieved as indicated by a markedly prolonged bleeding time and a more than 90% reduction in platelet counts (800/nl vs. 42/nl; P < 0.001). Functional (creatinine-clearance and proteinuria) parameters demonstrated no significant differences between the groups. Neither parameters of renal injury (glomerulosclerosis and fibrosis) nor glomerular/tubulointerstitial matrix expansion (by collagen IV staining), glomerular capillary rarefaction (lectin staining), and the glomerular/tubulointerstitial proliferative response (proliferating cell nuclear antigen) demonstrated any differences between platelet-depleted mice and PBS- or rat-IgG-treated nephritic mice at any time point. Despite effective platelet inhibition/depletion, neither the short- nor long-term course of passive crescentic nephrotoxic nephritis was affected. These data indicate that platelets play a minor role during the time course of this disease model in the mouse.

Is inflammation the cause of pre-eclampsia?

It has been proposed that either excessive inflammation or an imbalance in angiogenic factors cause pre-eclampsia. In the present review, the arguments for and against the role of inflammation and/or angiogenic imbalance as the cause of pre-eclampsia are discussed on the basis of the Bradford–Hill criteria for disease causation. Although both angiogenic imbalance and systemic inflammation are implicated in pre-eclampsia, the absence of temporality of inflammatory markers with pre-eclampsia challenges the concept that excessive inflammation is the cause of pre-eclampsia. In contrast, the elevation of anti-angiogenic factors that precede the clinical signs of pre-eclampsia fulfils the criterion of temporality. The second most important criterion is the dose–response relationship. Although such a relationship has not been proven between pro-inflammatory cytokines and pre-eclampsia, high levels of anti-angiogenic factors have been shown to correlate with increased incidence and disease severity, hence satisfying this condition. Finally, as the removal of circulating sFlt-1 (soluble Fms-like tyrosine kinase receptor-1) from pre-eclamptic patients significantly improves the clinical outcome, it fulfils the Hill's experiment principle, which states that removal of the cause by an appropriate experimental regimen should ameliorate the condition. In contrast, treatment with high doses of corticosteroid fails to improve maternal outcome in pre-eclampsia, despite suppressing inflammation. Inflammation may enhance the pathology induced by the imbalance in the angiogenic factors, but does not by itself cause pre-eclampsia. Development of therapies based on the angiogenic and cytoprotective mechanisms seems more promising.