Up-regulation of hepatocyte growth factor receptor: an amplification and targeting mechanism for hepatocyte growth factor action in acute renal failure

The injury-induced transcription factor SOX9 alters the expression of LBR, HMGA2, and HIPK3 in the human kidney

Induction of SRY box transcription factor 9 (SOX9) has been shown to occur in response to kidney injury in rodents, where SOX9-positive cells proliferate and regenerate the proximal tubules of injured kidneys. Additionally, SOX9-positive cells demonstrate a capacity to differentiate toward other nephron segments. Here, we characterized the role of SOX9 in normal and injured human kidneys. SOX9 expression was found to colocalize with a proportion of so-called scattered tubular cells in the uninjured kidney, a cell population previously shown to be involved in kidney injury and regeneration. Following injury and in areas adjacent to inflammatory cell infiltrates, SOX9-positive cells were increased in number. With the use of primary tubular epithelial cells (PTECs) obtained from human kidney tissue, SOX9 expression was spontaneously induced in culture and further increased by transforming growth factor-β1, whereas it was suppressed by interferon-γ. siRNA-mediated knockdown of SOX9 in PTECs followed by analysis of differential gene expression, immunohistochemical expression, and luciferase promoter assays suggested lamin B receptor (LBR), high mobility group AT-hook 2 (HMGA2), and homeodomain interacting protein kinase 3 (HIPK3) as possible target genes of SOX9. Moreover, a kidney explant model was used to demonstrate that only SOX9-positive cells survive the massive injury associated with kidney ischemia and that the surviving SOX9-positive cells spread and repopulate the tubules. Using a wound healing assay, we also showed that SOX9 positively regulated the migratory capacity of PTECs. These findings shed light on the functional and regulatory aspects of SOX9 activation in the human kidney during injury and regeneration.NEW & NOTEWORTHY Recent studies using murine models have shown that SRY box transcription factor 9 (SOX9) is activated during repair of renal tubular cells. In this study, we showed that SOX9-positive cells represent a proportion of scattered tubular cells found in the uninjured human kidney. Furthermore, we suggest that expression of LBR, HMGA2, and HIPK3 is altered by SOX9 in the kidney tubular epithelium, suggesting the involvement of these gene products in kidney injury and regeneration.

Renal Function Improvement Following ANG-3777 Treatment in Patients at High Risk for Delayed Graft Function After Kidney Transplantation

BACKGROUND

Patients (20%-50%) undergoing renal transplantation experience acute kidney injury resulting in delayed graft function. ANG-3777 is an hepatocyte growth factor mimetic that binds to the c-MET receptor. In animal models, ANG-3777 decreases apoptosis, increases proliferation, and promotes organ repair and function.

METHODS

This was a randomized, double-blind, placebo-controlled, phase 2 trial of patients undergoing renal transplantation with <50 cc/h urine output for 8 consecutive hours over the first 24 hours posttransplantation, or creatinine reduction ratio <30% from pretransplantation to 24 hours posttransplantation. Subjects were randomized as 2:1 to 3, once-daily IV infusions of ANG-3777, 2 mg/kg (n = 19), or placebo (n = 9). Primary endpoint: time in days to achieve ≥1200 cc urine for 24 hours.

RESULTS

Patients treated with ANG-3777 were more likely to achieve the primary endpoint of 1200 cc urine for 24 hours by 28 days posttransplantation (83.3% versus 50% placebo; log-rank test: χ2 = 2.799, P = 0.09). Compared with placebo, patients in the ANG-3777 arm had larger increases in urine output; lower serum creatinine; greater reduction in C-reactive protein and neutrophil gelatinase-associated lipocalin; fewer dialysis sessions and shorter duration of dialysis; fewer hospital days; significantly less graft failure; and higher estimated glomerular filtration rate. Adverse events occurred in a similar percentage of subjects in both arms. Events per subject were twice as high in the placebo arm.

CONCLUSIONS

There was an efficacy signal for improved renal function in subjects treated with ANG-3777 relative to placebo, with a good safety profile.

HGF/MET Signaling in Malignant Brain Tumors

Hepatocyte growth factor (HGF) ligand and its receptor tyrosine kinase (RTK) mesenchymal-epithelial transition factor (MET) are important regulators of cellular processes such as proliferation, motility, angiogenesis, and tissue regeneration. In healthy adult somatic cells, this ligand and receptor pair is expressed at low levels and has little activity except when tissue injuries arise. In cancer cells, HGF/MET are often overexpressed, and this overexpression is found to correlate with tumorigenesis, metastasis, and poorer overall prognosis. This review focuses on the signaling of these molecules in the context of malignant brain tumors. RTK signaling pathways are among the most common and universally dysregulated pathways in gliomas. We focus on the role of HGF/MET in the following primary malignant brain tumors: astrocytomas, glioblastomas, oligodendrogliomas, ependymomas, and embryonal central nervous system tumors (including medulloblastomas and others). Brain metastasis, as well as current advances in targeted therapies, are also discussed.

Hepatocyte Growth Factor Mimetic ANG-3777 for Cardiac Surgery-Associated Acute Kidney Injury

Introduction

Nearly one-third of patients undergoing cardiac surgery involving cardiopulmonary bypass (CPB) experience cardiac surgery–associated (CSA) acute kidney injury (AKI); 5% require renal replacement therapy. ANG-3777 is a hepatocyte growth factor mimetic. In vitro, ANG-3777 reduces apoptosis and increases cell proliferation, migration, morphogenesis, and angiogenesis in injured kidneys. In animal models, ANG-3777 mitigates the effects of renal damage secondary to ischemia reperfusion injury and nephrotoxic chemicals. Phase 2 data in AKI of renal transplantation have shown improved renal function and comparable safety relative to placebo. The Guard Against Renal Damage (GUARD) study is a phase 2 proof of concept trial of ANG-3777 in CSA-AKI.

Methods

GUARD is a 240-patient, multicenter, double-blind, randomized placebo-controlled trial to assess the efficacy and safety of ANG-3777 in patients at elevated pre-surgery risk for AKI undergoing coronary artery bypass graft (CABG) or heart valve repair/replacement requiring CPB. Subjects are randomized 1:1 to receive ANG-3777 (2 mg/kg) or placebo. Study drug is dosed via 4 daily intravenous 30-minute infusions. The first dose is administered less than 4 hours after completing CPB, second at 24 ± 2 hours post-CPB, with two subsequent doses at 24 ± 2 hours after the previous dose.

Results

The primary efficacy endpoint is percent change from baseline serum creatinine to mean area under the curve from days 2 through 6. Secondary endpoints include change in estimated glomerular filtration rate from baseline to day 30, the proportion of patients diagnosed with AKI by stage through day 5, and the length of CSA-AKI hospitalization. Safety will include adverse events and laboratory measures.

Conclusion

This phase 2 study of ANG-3777 provides data to develop a phase 3 registrational study in this medically complex condition.

Potential targeted therapy and diagnosis based on novel insight into growth factors, receptors, and downstream effectors in acute kidney injury and acute kidney injury-chronic kidney disease progression

Acute kidney injury (AKI) is defined as a rapid decline in renal function and is characterized by excessive renal inflammation and programmed death of resident cells. AKI shows high morbidity and mortality, and severe or repeated AKI can transition to chronic kidney disease (CKD) or even end-stage renal disease (ESRD); however, very few effective and specific therapies are available, except for supportive treatment. Growth factors, such as epidermal growth factor (EGF), insulin-like growth factor (IGF), and transforming growth factor-β (TGF-β), are significantly altered in AKI models and have been suggested to play critical roles in the repair process of AKI because of their roles in cell regeneration and renal repair. In recent years, a series of studies have shown evidence that growth factors, receptors, and downstream effectors may be highly involved in the mechanism of AKI and may function in the early stage of AKI in response to stimuli by regulating inflammation and programmed cell death. Moreover, certain growth factors or correlated proteins act as biomarkers for AKI due to their sensitivity and specificity. Furthermore, growth factors originating from mesenchymal stem cells (MSCs) via paracrine signaling or extracellular vesicles recruit leukocytes or repair intrinsic cells and may participate in AKI repair or the AKI-CKD transition. In addition, growth factor-modified MSCs show superior therapeutic potential compared to that of unmodified controls. In this review, we summarized the current therapeutic and diagnostic strategies targeting growth factors to treat AKI in clinical trials. We also evaluated the possibilities of other growth factor-correlated molecules as therapeutic targets in the treatment of AKI and the AKI-CKD transition.

Drugs in Development for Acute Kidney Injury

The care of patients with acute kidney injury (AKI) has been limited due to the lack of effective therapeutics that can either prevent AKI during high-risk situations or treat AKI once established. A revolution in the scientific understanding of the pathogenesis of AKI has led to the identification of potential therapeutic targets. These targets include pathways involved in inflammation, cellular repair and fibrosis, cellular metabolism and mitochondrial function, oxidative stress, apoptosis, and hemodynamics and oxygen delivery. Many compounds are entering early-phase clinical trials. In addition, efforts to better describe sub-categories of AKI (through endo-phenotyping) hold promise to target therapies more effectively based upon pathways that are operative in the pathogenesis. These advances bring optimism that the care of patients with AKI will be transformed with the hope of better outcomes.

Syndecan-1 Shedding Inhibition to Protect Against Ischemic Acute Kidney Injury Through HGF Target Signaling Pathway

BACKGROUND

The hepatocyte growth factor (HGF) target pathway plays pivotal renoprotective roles after acute kidney injury. Syndecan-1 (SDC-1) serves as the coreceptor for HGF. Shedding of SDC-1 is involved in various pathological processes. Thus, we hypothesized that ischemia/reperfusion injury induced SDC-1 shedding, and inhibiting SDC-1 shedding would protect against kidney injury by potentiating activation of the HGF receptor mesenchymal epithelial transition factor (c-Met).

METHODS

Expression of SDC-1 and its sheddases were observed in kidneys of sham and ischemia/reperfusion (I/R) mice. To inhibit SDC-1 shedding, mice were injected with the sheddase inhibitor GM6001 before I/R surgery, and then, renal inflammation, tubular apoptosis, and activation of the c-Met/AKT/glycogen synthase kinase-3β (GSK-3β) pathway were analyzed. In vitro, human proximal tubular cell lines were pretreated with GM6001 under hypoxia/reperfusion conditions. The apoptosis and viability of cells and expression of c-Met/AKT/GSK-3β pathway components were evaluated. The relationship was further confirmed by treatment with SU11274, a specific inhibitor of phospho-c-Met.

RESULTS

Shedding of SDC-1 was induced after ischemia/reperfusion injury both in vivo and in vitro. GM6001 pretreatment suppressed SDC-1 shedding, alleviated renal inflammation and tubular apoptosis, and upregulated phosphorylation of the c-Met/AKT/GSK-3β pathway. In vitro, pretreatment with GM6001 also decreased hypoxia/reperfusion-induced cell apoptosis and promoted activation of the c-Met pathway. In addition, the cytoprotective role of GM6001 was attenuated by suppressing c-Met phosphorylation with SU11274.

CONCLUSIONS

Our findings suggest that inhibiting I/R-induced SDC-1 shedding protected against ischemic acute kidney injury by potentiating the c-Met/AKT/GSK-3β pathway.

Recruited T cells promote the bladder cancer metastasis via up-regulation of the estrogen receptor β/IL-1/c-MET signals

Clinical data indicates that T cells can be recruited to bladder cancer (BCa), yet the impact of T cells on BCa progression remains unclear. In the present study, we found that T cells were recruited more to BCa tissues than to the surrounding normal bladder tissues. Results from an in vitro co-culture system also found that BCa recruited more CD4⁺ T cells than did normal bladder cells. The recruiting of T cells to BCa tissues may increase the proliferation and invasion of BCa cells. Mechanistic studies revealed that infiltrating T cells stimulate BCa estrogen receptor beta (ERβ) signaling and consequently increase the expression of MET proto-oncogene, receptor tyrosine kinase (c-MET), through either direct binding to its promoter or via modulation of IL-1 expression. Interruption of ERβ/c-MET or ERβ/IL-1/c-MET signaling via ERβ-shRNA, IL-1 antagonist, or the c-MET inhibitor, SU11274, could partially reverse the T cell-enhanced BCa cell invasion and proliferation. Finally, the mouse BCa model with xenografted BCa 5637 cells with T (HH) cells confirmed the results of in vitro co-culture studies showing that infiltrating T cells could promote BCa metastasis via modulation of the ERβ/c-MET or ERβ/IL-1/c-MET signaling pathways. These findings may provide a new therapeutic approach to better combat BCa progression via targeting these newly identified signaling pathways.

High glucose induces HGF-independent activation of Met receptor in human renal tubular epithelium

CONTEXT

The role of hepatocyte growth factor (HGF) in diabetic kidney damage remains controversial.

OBJECTIVE

To test the hypothesis that high glucose levels activate pathways related to HGF and its receptor Met and that this could participate in glucose-induced renal cell damage.

MATERIALS AND METHODS

HK2 cells, a human proximal tubule epithelial cell line, were stimulated with high glucose for 48 hours. Levels of pMet/Met, pEGFR/EGFR, pSTAT3/STAT3, pAkt/Akt and pERK1/2/ERK1/2 were studied by immunoblotting. Absence of HGF was verified by qRT-PCR and ELISA.

RESULTS

High glucose level activated Met and its downstream pathways STAT3, Akt and ERK independently of HGF. High glucose induced an integrin ligand fibronectin. HGF-independent Met phosphorylation was prevented by inhibition of integrin α5β1, Met inhibitor crizotinib, Src inhibitors PP2 and SU5565, but not by EGFR inhibitor AG1478. High glucose increased the expression of TGFβ-1, CTGF and the tubular damage marker KIM-1 and increased apoptosis of HK2 cells, effects inhibited by crizotinib.

CONCLUSION

High glucose activated Met receptor in HK2 cells independently of HGF, via induction of integrin α5β1 and downstream signaling. This mode of Met activation was associated with tubular cell damage and apoptosis and it may represent a novel pathogenic mechanism and a treatment target in diabetic nephropathy.

Recent early clinical drug development for acute kidney injury

INTRODUCTION

Despite significant need and historical trials, there are no effective drugs in use for the prevention or treatment of acute kidney injury (AKI). There are several promising agents in early clinical development for AKI and two trials have recently been terminated. There are also exciting new findings in pre-clinical AKI research. There is a need to take stock of current progress in the field to guide future drug development for AKI. Areas covered: The main clinical trial registries, PubMed and pharmaceutical company website searches were used to extract the most recent clinical trials for sterile, transplant and sepsis-associated AKI. We summarise the development of the agents recently in clinical trial, update on their trial progress, consider reasons for failed efficacy of two agents, and discuss new paradigms in pre-clinical targets for AKI. Agents covered include- QPI-1002, THR-184, BB-3, heme arginate, human recombinant alkaline phosphatase (recAP), ciclosporin A, AB103, levosimendan, AC607 and ABT-719. Expert opinion: Due to the heterogenous nature of AKI, agents with the widest pleiotropic effects on multiple pathophysiological pathways are likely to be most effective. Linking preclinical models to clinical indication and improving AKI definition and diagnosis are key areas for improvement in future clinical trials.

Urinary biomarkers are associated with incident cardiovascular disease, all-cause mortality and deterioration of kidney function in type 2 diabetic patients with microalbuminuria

AIMS/HYPOTHESIS

We evaluated two urinary biomarkers reflecting different aspects of renal pathophysiology as potential determinants of incident cardiovascular disease (CVD), all-cause mortality and a reduced estimated GFR (eGFR) in patients with type 2 diabetes and microalbuminuria but without clinical features of coronary artery disease.

METHODS

In a prospective study of 200 patients, all received multifactorial treatment. Baseline measurements of urinary hepatocyte growth factor (HGF) and adiponectin were available for 191 patients. Cox models were adjusted for sex, age, LDL-cholesterol, smoking, HbA1c, plasma creatinine, systolic BP and urinary AER (UAER). The pre-defined endpoint of chronic kidney disease progression was a decline in the eGFR of >30% during follow-up. HRs per 1 SD increment of log-transformed values are presented.

RESULTS

Patients had a mean ± SD age of 59 ± 9 years with a median (interquartile range) UAER of 103 (39-230) mg/24 h. During a median 6.1 years of follow-up, there were 40 incident CVD events, 26 deaths and 42 patients reached the pre-defined chronic kidney disease progression endpoint after 4.9 years (median). Higher urinary HGF was a determinant of CVD in unadjusted (HR 1.9 [95% CI 1.3, 2.8], p = 0.001) and adjusted (HR 2.0 [95% CI 1.2, 3.2], p = 0.004) models, and of all-cause mortality in unadjusted (HR 2.3 [95% CI 1.3, 3.9], p = 0.003) and adjusted (HR 2.5 [95% CI 1.3, 4.8], p = 0.005) models. A higher adiponectin level was associated with CVD in unadjusted (HR 1.4 [95% CI 1.0, 1.9], p = 0.04) and adjusted (HR 1.4 [95% CI 1.1, 2.3], p = 0.013) models, and with a decline in the eGFR of >30% in unadjusted (HR 1.6 [95% CI 1.2, 2.2], p = 0.008) and adjusted (HR 1.5 [95% CI 1.1, 2.2], p = 0.007) models.

CONCLUSIONS/INTERPRETATION

In patients with type 2 diabetes and microalbuminuria receiving multifactorial treatment, higher urinary HGF was associated with incident CVD and all-cause mortality, and higher adiponectin was associated with CVD and deterioration in renal function.

Late intervention with the small molecule BB3 mitigates postischemic kidney injury

Ischemia-reperfusion-mediated acute kidney injury can necessitate renal replacement therapy and is a major cause of morbidity and mortality. We have identified BB3, a small molecule, which when first administered at 24 h after renal ischemia in rats, improved survival, augmented urine output, and reduced the increase in serum creatinine and blood urea nitrogen. Compared with control kidneys, the kidneys of BB3-treated animals exhibited reduced levels of kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, and reduced tubular apoptosis and acute tubular necrosis but enhanced tubular regeneration. Consistent with its hepatocyte growth factor-like mode of action, BB3 treatment promoted phosphorylation of renal cMet and Akt and upregulated renal expression of the survival protein Bcl-2. These data suggest that the kidney is amenable to pharmacotherapy even 24 h after ischemia-reperfusion and that activation of the hepatocyte growth factor signaling pathway with the small molecule BB3 confers interventional benefits late into ischemia-reperfusion injury. These data formed, in part, the basis for the use of BB3 in a clinical trial in kidney recipients presenting with delayed graft function.

The cytohesin guanosine exchange factors (GEFs) are required to promote HGF-mediated renal recovery after acute kidney injury (AKI) in mice

The lack of current treatment and preventable measures for acute kidney injury (AKI) in hospitalized patients results in an increased mortality rate of up to 80% and elevated health costs. Additionally, if not properly repaired, those who survive AKI may develop fibrosis and long-term kidney damage. The molecular aspects of kidney injury and repair are still uncertain. Hepatocyte growth factor (HGF) promotes recovery of the injured kidney by inducing survival and migration of tubular epithelial cells to repopulate bare tubule areas. HGF-stimulated kidney epithelial cell migration requires the activation of ADP-ribosylation factor 6 (Arf6) and Rac1 via the cytohesin family of Arf-guanine-nucleotide exchange factors (GEFs), in vitro. We used an ischemia and reperfusion injury (IRI) mouse model to analyze the effects of modulating this signaling pathway on kidney recovery. We treated IRI mice with either HGF, the cytohesin inhibitor SecinH3, or a combination of both. As previously reported, HGF treatment promoted rapid improvement of kidney function as evidenced by creatinine (Cre) and blood urea nitrogen (BUN) levels. In contrast, simultaneous treatment with SecinH3 and HGF blocks the ability of HGF to promote kidney recovery. Immunohistochemistry showed that HGF treatment promoted recovery of tubule structure, and had enhanced levels of active, GTP-bound Arf6 and GTP-Rac1. SecinH3 treatment, however, caused a dramatic decrease in GTP-Arf6 and GTP-Rac1 levels when compared to kidney sections from HGF-treated IRI mice. Additionally, SecinH3 counteracted the renal reparative effects of HGF. Our results support the conclusion that cytohesin function is required for HGF-stimulated renal IRI repair.

Hepatocyte Growth Factor Isoforms in Tissue Repair, Cancer, and Fibrotic Remodeling

Hepatocyte growth factor (HGF), also known as scatter factor (SF), is a pleotropic factor required for normal organ development during embryogenesis. In the adult, basal expression of HGF maintains tissue homeostasis and is up-regulated in response to tissue injury. HGF expression is necessary for the proliferation, migration, and survival of epithelial and endothelial cells involved in tissue repair in a variety of organs, including heart, lung, kidney, liver, brain, and skin. The administration of full length HGF, either as a protein or using exogenous expression methodologies, increases tissue repair in animal models of tissue injury and increases angiogenesis. Full length HGF is comprised of an N-terminal hairpin turn, four kringle domains, and a serine protease-like domain. Several naturally occurring alternatively spliced isoforms of HGF were also identified. The NK1 variant contains the N-terminal hairpin and the first kringle domain, and the NK2 variant extends through the second kringle domain. These alternatively spliced forms of HGF activate the same receptor, MET, but they differ from the full length protein in their cellular activities and their biological functions. Here, we review the species-specific expression of the HGF isoforms, their regulation, the signal transduction pathways they activate, and their biological activities.

Intercellular transfer of GPRC5B via exosomes drives HGF-mediated outward growth

How cells communicate during development and regeneration is a critical question. One mechanism of intercellular communication is via exosomes, extracellular vesicles that originate by the fusion of multivesicular endosomes with the plasma membrane [1-8]. To model exosome-based intercellular communication, we used Madin-Darby canine kidney (MDCK) cell cysts grown in 3D gels of extracellular matrix, which form tubules in response to hepatocyte growth factor (HGF). We report that GPRC5B, an orphan G protein coupled receptor, is in exosomes produced by HGF-treated cysts and released into the cyst lumen. Exosomal GPRC5B is taken up by nearby cells and together with HGF promotes extracellular signal-regulated kinase 1/2 (ERK1/2) activation and tubulogenesis, even under conditions where tubulogenesis would otherwise not occur. Recovery from injury, such as acute kidney injury (AKI), often recapitulates developmental processes. Here, we show that GPRC5B is elevated in urinary exosomes from patients with AKI. Our results elucidate how GPRC5B is carried by exosomes and augments HGF-induced morphogenesis. The unexpected role of exosomes in transporting GPRC5B between cells during morphogenesis and the ability of GPRC5B to predict the disease state of AKI elucidate a novel mechanism for intercellular communication during development and repair.

Investigating the Relationship between Serum Level of s-Met (Soluble Hepatic Growth Factor Receptor) and Preeclampsia in the First and Second Trimesters of Pregnancy

Introduction. Preeclampsia (PE) is an important cause of mortality and morbidity for mothers, fetuses, and the newborns. Placenta plays a pivotal role in pathogenesis of PE. Hepatic growth factor (HGF) is a cytokine expressed by the mesenchymal stalk of placental villi during pregnancy and assumes a paracrine role in trophoblasts which express its receptor (c-MET). In the present study, we investigate the diagnostic value of s-Met (the soluble form of the receptor) in the first and second trimesters of pregnancy for early diagnosis of preeclampsia. Method and Materials. This is a case-control study conducted on 95 pregnant women. The serum level of s-Met was measured in the first and second trimesters, and the participants were followed until delivery. 44 individuals with preeclampsia (the case group) and 51 individuals without preeclampsia (the control group) were evaluated. Results. Serum level of s-Met in preeclamptic participants was lower than that of the control group in both the first and the second trimesters (P < 0.0001). In addition, serum levels of s-Met were significantly lower during the first and second trimesters in patients with early, severe preeclampsia compared to those with late, mild preeclampsia (P < 0.0001). The sensitivity and specificity of s-Met in the first and second trimesters were, respectively, (83%, 94%) and (77%, 94%) for early preeclampsia and (88%, 92%) and (86%, 98%) for severe preeclampsia. Conclusion. Considering our findings, serum level of s-Met may be used as a predictive factor for early detection of preeclampsia. Further research is required to corroborate the functional and therapeutic value of s-Met in preeclampsia.

Activation of hepatocyte growth factor receptor, c-met, in renal tubules is required for renoprotection after acute kidney injury

Hepatocyte growth factor is a pleiotrophic protein that promotes injury repair and regeneration in multiple organs. Here, we show that after acute kidney injury (AKI), the HGF receptor, c-met, was induced predominantly in renal tubular epithelium. To investigate the role of tubule-specific induction of c-met in AKI, we generated conditional knockout mice, in which the c-met gene was specifically disrupted in renal tubules. These Ksp-met−/−mice were phenotypically normal and had no appreciable defect in kidney morphology and function. However, in AKI induced by cisplatin or ischemia-reperfusion injury, the loss of tubular c-met substantially aggravated renal injury. Compared with controls, Ksp-met−/−mice displayed higher serum creatinine, more severe morphologic lesions, and increased apoptosis, which was accompanied by an increased expression of Bax and Fas ligand and decreased phosphorylation-activation of Akt. In addition, ablation of c-met in renal tubules promoted chemokine expression and renal inflammation after AKI. Consistently, ectopic expression of hepatocyte growth factor in vivo protected the kidneys against AKI in control mice, but not in Ksp-met−/−counterparts. Thus, our results suggest that tubule-specific c-met signaling is crucial in conferring renal protection after AKI, primarily by its anti-apoptotic and anti-inflammatory mechanisms.

EMD 1214063 and EMD 1204831 constitute a new class of potent and highly selective c-Met inhibitors

PURPOSE

The mesenchymal-epithelial transition factor (c-Met) receptor, also known as hepatocyte growth factor receptor (HGFR), controls morphogenesis, a process that is physiologically required for embryonic development and tissue repair. Aberrant c-Met activation is associated with a variety of human malignancies including cancers of the lung, kidney, stomach, liver, and brain. In this study, we investigated the properties of two novel compounds developed to selectively inhibit the c-Met receptor in antitumor therapeutic interventions.

EXPERIMENTAL DESIGN

The pharmacologic properties, c-Met inhibitory activity, and antitumor effects of EMD 1214063 and EMD 1204831 were investigated in vitro and in vivo, using human cancer cell lines and mouse xenograft models.

RESULTS

EMD 1214063 and EMD 1204831 selectively suppressed the c-Met receptor tyrosine kinase activity. Their inhibitory activity was potent [inhibitory 50% concentration (IC50), 3 nmol/L and 9 nmol/L, respectively] and highly selective, when compared with their effect on a panel of 242 human kinases. Both EMD 1214063 and EMD 1204831 inhibited c-Met phosphorylation and downstream signaling in a dose-dependent fashion, but differed in the duration of their inhibitory activity. In murine xenograft models, both compounds induced regression of human tumors, regardless of whether c-Met activation was HGF dependent or independent. Both drugs were well tolerated and induced no substantial weight loss after more than 3 weeks of treatment.

CONCLUSIONS

Our results indicate selective c-Met inhibition by EMD 1214063 and EMD 1204831 and strongly support clinical testing of these compounds in the context of molecularly targeted anticancer strategies.

Dephosphorylated Ser985 of c-Met is associated with acquired resistance to rechallenge injury in rats that had recovered from uranyl acetate-induced subclinical renal damage

BACKGROUND

We previously reported that rats that had recovered from mild proximal tubule (PT) injury induced by a sub-toxic dose of uranyl acetate (UA) showed partial resistance to a subsequent nephrotoxic dose of UA in association with reduced renal dysfunction and accelerated PT proliferation. We demonstrated that this resistance may involve hepatocyte growth factor (HGF)/c-Met signaling. Here, we examined whether primary cultured tubular cells derived from this model had acquired sensitivity to HGF.

METHODS

Tubular cells were isolated by collagenase digestion from rat kidneys after recovery from UA-induced mild PT injury and were cultured for 48 h. Their survival and proliferation were examined using the MTS assay/5-bromo-2'-deoxyuridine labeling or MTS assay, respectively, and their migration was assayed using wound-healing and cell scattering assays, with/without HGF. HGF/c-Met signaling was assayed using phospho-specific antibodies.

RESULTS

HGF-stimulated cultured tubular cells from UA-treated rats showed better survival after UA exposure and higher proliferation and migration than cells from vehicle-treated rats. Furthermore, HGF induced higher phosphorylation of c-Met (Tyr1234/1235) and of its major downstream signals (AKT and extracellular signal-regulated kinase 1/2) with maintained dephosphorylation of Ser985 as a negative regulator of HGF/c-Met signaling in the tubular cells of UA-treated rats compared to those of vehicle-treated rats. Immunohistochemically, dephosphorylated Ser985 was confirmed in PT cells in vivo.

CONCLUSIONS

These results suggest that elevated sensitivity to HGF, via dephosphorylated Ser985 of c-Met of tubular cells that had recovered from mild tubular injury, may be associated with cytoprotection, accelerated proliferation and migration.

Discovery and validation of a molecular signature for the noninvasive diagnosis of human renal allograft fibrosis

BACKGROUND

Tubulointerstitial fibrosis (fibrosis), a histologic feature associated with a failing kidney allograft, is diagnosed using the invasive allograft biopsy. A noninvasive diagnostic test for fibrosis may help improve allograft outcome.

METHODS

We obtained 114 urine specimens from 114 renal allograft recipients: 48 from 48 recipients with fibrosis in their biopsy results and 66 from 66 recipients with normal biopsy results. Levels of messenger RNAs (mRNAs) in urinary cells were measured using kinetic, quantitative polymerase chain reaction assays, and the levels were related to allograft diagnosis. A discovery set of 76 recipients (32 with allograft fibrosis and 44 with normal biopsy results) was used to develop a diagnostic signature, and an independent validation set of 38 recipients (16 with allograft fibrosis and 22 with normal biopsy results) was used to validate the signature.

RESULTS

In the discovery set, urinary cell levels of the following mRNAs were significantly associated with the presence of allograft fibrosis: vimentin (P<0.0001, logistic regression model), hepatocyte growth factor (P<0.0001), α-smooth muscle actin (P<0.0001), fibronectin 1 (P<0.0001), perforin (P=0.0002), plasminogen activator inhibitor 1 (P=0.0002), transforming growth factor β1 (P=0.0004), tissue inhibitor of metalloproteinase 1 (P=0.0009), granzyme B (P=0.0009), fibroblast-specific protein 1 (P=0.006), CD103 (P=0.02), and collagen 1A1 (P=0.04). A four-gene model composed of the levels of mRNA for vimentin, NKCC2, and E-cadherin and of 18S ribosomal RNA provided the most accurate, parsimonious diagnostic model of allograft fibrosis with a sensitivity of 93.8% and a specificity of 84.1% (P<0.0001). In the independent validation set, this same model predicted the presence of allograft fibrosis with a sensitivity of 77.3% and a specificity of 87.5% (P<0.0001).

CONCLUSIONS

Measurement of mRNAs in urinary cells may offer a noninvasive means of diagnosing fibrosis in human renal allografts.

Tubule-specific ablation of endogenous β-catenin aggravates acute kidney injury in mice

β-Catenin is a unique intracellular protein functioning as an integral component of the cell-cell adherens complex and a principal signaling protein mediating canonical Wnt signaling. Little is known about its function in adult kidneys in the normal physiologic state or after acute kidney injury (AKI). To study this, we generated conditional knockout mice in which the β-catenin gene was specifically disrupted in renal tubules (Ksp-β-cat-/-). These mice were phenotypically normal with no appreciable defects in kidney morphology and function. In the absence of β-catenin, γ-catenin functionally substituted for it in E-cadherin binding, thereby sustaining the integrity of epithelial adherens junctions in the kidneys. In AKI induced by ischemia reperfusion or folic acid, the loss of tubular β-catenin substantially aggravated renal lesions. Compared with controls, Ksp-β-cat-/- mice displayed higher mortality, elevated serum creatinine, and more severe morphologic injury. Consistently, apoptosis was more prevalent in kidneys of the knockout mice, which was accompanied by increased expression of p53 and Bax, and decreased phosphorylated Akt and survivin. In vitro activation of β-catenin by Wnt1 or stabilization of β-catenin protected tubular epithelial cells from apoptosis, activated Akt, induced survivin, and repressed p53 and Bax expression. Hence, endogenous β-catenin is pivotal for renal tubular protection after AKI by promoting cell survival through multiple mechanisms.

Bench-to-bedside review: Ventilation-induced renal injury through systemic mediator release--just theory or a causal relationship?

We review the current literature on the molecular mechanisms involved in the pathogenesis of acute kidney injury induced by plasma mediators released by mechanical ventilation. A comprehensive literature search in the PubMed database was performed and articles were identified that showed increased plasma levels of mediators where the increase was solely attributable to mechanical ventilation. A subsequent search revealed articles delineating the potential effects of each mediator on the kidney or kidney cells. Limited research has focused specifically on the relationship between mechanical ventilation and acute kidney injury. Only a limited number of plasma mediators has been implicated in mechanical ventilation-associated acute kidney injury. The number of mediators released during mechanical ventilation is far greater and includes pro- and anti-inflammatory mediators, but also mediators involved in coagulation, fibrinolysis, cell adhesion, apoptosis and cell growth. The potential effects of these mediators is pleiotropic and include effects on inflammation, cell recruitment, adhesion and infiltration, apoptosis and necrosis, vasoactivity, cell proliferation, coagulation and fibrinolysis, transporter regulation, lipid metabolism and cell signaling. Most research has focused on inflammatory and chemotactic mediators. There is a great disparity of knowledge of potential effects on the kidney between different mediators. From a theoretical point of view, the systemic release of several mediators induced by mechanical ventilation may play an important role in the pathophysiology of acute kidney injury. However, evidence supporting a causal relationship is lacking for the studied mediators.

Combined paracrine and endocrine AAV9 mediated expression of hepatocyte growth factor for the treatment of renal fibrosis

In chronic renal disease, tubulointerstitial fibrosis is a leading cause of renal failure. Here, we made use of one of the most promising gene therapy vector platforms, the adeno-associated viral (AAV) vector system, and the COL4A3-deficient mice, a genetic mouse model of renal tubulointerstitial fibrosis, to develop a novel bidirectional treatment strategy to prevent renal fibrosis. By comparing different AAV serotypes in reporter studies, we identified AAV9 as the most suitable delivery vector to simultaneously target liver parenchyma for endocrine and renal tubular epithelium for paracrine therapeutic expression of the antifibrogenic cytokine human hepatocyte growth factor (hHGF). We used transcriptional targeting to drive hHGF expression from the newly developed CMV-enhancer-Ksp-cadherin-promoter (CMV-Ksp) in renal and hepatic tissue following tail vein injection of rAAV9-CMV-Ksp-hHGF into COL4A3-deficient mice. The therapeutic efficiency of our approach was demonstrated by a remarkable attenuation of tubulointerstitial fibrosis and repression of fibrotic markers such as collagen1alpha1 (Col1A1), platelet-derived growth factor receptor-beta (PDGFR-beta), and alpha-smooth muscle actin (SMA). Taken together, our results show the great potential of rAAV9 as an intravenously applicable vector for the combined paracrine and endocrine expression of antifibrogenic factors in the treatment of renal failure caused by tubulointerstitial fibrosis.

Plasma level of soluble c-Met is tightly associated with the clinical risk of preeclampsia

OBJECTIVE

The objective of the study was to examine the relevance of the soluble form c-Met (sMet) with the clinical risk for severe preeclampsia.

STUDY DESIGN

This prospective case-control study was performed by using plasma derived from 44 preeclamptic and 51 uncomplicated pregnant women. Plasma concentration of sMet was measured with specific enzyme-linked immunosorbent assay, and the predictive values were determined based on the receiver-operating characteristic (ROC) curves analysis.

RESULTS

Plasma s-Met level in normal pregnant women changed in a gestation-dependent manner, peaking at weeks 19-24. In women with severe preeclampsia, the circulating sMet level was significantly lower than that in the gestational stage-matched controls during gestational weeks 15-30. The ROC curve analysis revealed a significant correlation between plasma sMet level and the risk of developing severe preeclampsia.

CONCLUSION

Plasma sMet could serve as a potential biomarker for predicting severe preeclampia at early second trimester of pregnancy.

Antifolate/folate-activated HGF/c-Met signalling pathways in mouse kidneys-the putative role of their downstream effectors in cross-talk with androgen receptor

This in vivo study of mouse kidneys was focused on the identification of protein mediators involved in the cross-talk between two signalling pathways. One pathway was triggered by testosterone via an androgen receptor, AR, and the other induced by CB 3717/folate via HGF, and its membrane receptor c-Met. Sequential activation of these pathways leads to a drastic decrease of testosterone-induced ornithine decarboxylase, ODC, expression. We proved that CB 3717/folate-induced ODC expression is Akt-dependent. CB 3717/folate activates Akt and ERK1/2 kinases, PTEN phosphatase and also up-regulates cyclin D2 and PCNA, but decreases GSK3beta and cyclin D1 protein levels. Testosterone activation of AR induces GSK3beta and PTEN. Results of the sequential activation of the studied signalling pathways suggest that Akt, GSK3beta and possibly ERK1/2 kinases may participate in the negative cross-talk and attenuation of AR transactivity, while the involvement of PTEN and cyclin D1 seems to be doubtful.

Angiotensin receptor subtype mediated physiologies and behaviors: new discoveries and clinical targets

The renin-angiotensin system (RAS) mediates several classic physiologies including body water and electrolyte homeostasis, blood pressure, cyclicity of reproductive hormones and sexual behaviors, and the regulation of pituitary gland hormones. These functions appear to be mediated by the angiotensin II (AngII)/AT(1) receptor subtype system. More recently, the angiotensin IV (AngIV)/AT(4) receptor subtype system has been implicated in cognitive processing, cerebroprotection, local blood flow, stress, anxiety and depression. There is accumulating evidence to suggest an inhibitory influence by AngII acting at the AT(1) subtype, and a facilitory role by AngIV acting at the AT(4) subtype, on neuronal firing rate, long-term potentiation, associative and spatial learning, and memory. This review initially describes the biochemical pathways that permit synthesis and degradation of active angiotensin peptides and three receptor subtypes (AT(1), AT(2) and AT(4)) thus far characterized. There is vigorous debate concerning the identity of the most recently discovered receptor subtype, AT(4). Descriptions of classic and novel physiologies and behaviors controlled by the RAS are presented. This review concludes with a consideration of the emerging therapeutic applications suggested by these newly discovered functions of the RAS.

Inhibition of tubular cell proliferation by neutralizing endogenous HGF leads to renal hypoxia and bone marrow-derived cell engraftment in acute renal failure

During the progression of acute renal failure (ARF), the renal tubular S3 segment is sensitive to ischemic stresses. For reversing tubular damage, resident tubular cells proliferate, and bone marrow-derived cells (BMDC) can be engrafted into injured tubules. However, how resident epithelium or BMDC are involved in tubular repair remains unknown. Using a mouse model of ARF, we examined whether hepatocyte growth factor (HGF) regulates a balance of resident cell proliferation and BMDC recruitment. Within 48 h post-renal ischemia, tubular destruction became evident, followed by two-waved regenerative events: 1) tubular cell proliferation between 2 and 4 days, along with an increase in blood HGF; and 2) appearance of BMDC in the tubules from 6 days postischemia. When anti-HGF IgG was injected in the earlier stage, tubular cell proliferation was inhibited, leading to an increase in BMDC in renal tubules. Under the HGF-neutralized state, stromal cell-derived factor-1 (SDF1) levels increased in renal tubules, associated with the enhanced hypoxia. Administrations of anti-SDF1 receptor IgG into ARF mice reduced the number of BMDC in interstitium and tubules. Thus possible cascades include 1) inhibition of tubular cell proliferation by neutralizing HGF leads to renal hypoxia and SDF1 upregulation; and 2) BMDC are eventually engrafted in tubules through SDF1-mediated chemotaxis. Inversely, administration of recombinant HGF suppressed the renal hypoxia, SDF1 upregulation, and BMDC engraftment in ARF mice by enhancing resident tubular cell proliferation. Thus we conclude that HGF is a positive regulator for eliciting resident tubular cell proliferation, and SDF1 for BMDC engraftment during the repair process of ARF.

Growth factors temporally associate with airway responsiveness and inflammation in allergen-exposed mice

BACKGROUND

To clarify whether growth factors play critical roles in the development of airway hyperresponsiveness (AHR) and airway inflammation in the early stages of asthma, the relationship between growth factors and AHR and airway inflammation were analyzed in a mouse model of asthma.

METHODS

Following ovalbumin (OVA) sensitization and challenge, airway function, inflammation, cytokine and growth factor levels were monitored.

RESULTS

AHR to inhaled methacholine increased at 6 h, peaked at 48 h, and remained elevated for 14 days. IL-4 and IL-5 levels in bronchoalveolar lavage (BAL) fluid were increased at 6 h, peaked at 24 h, but returned to baseline quickly. IL-13 levels increased up to 14 days, peaking at 48 h. Increases in BAL fluid transforming growth factor-beta(1) and platelet-derived growth factor were observed at 12 h, and remained elevated at 14 days. Nerve growth factor levels were increased at 24-28 days. BAL fluid hepatocyte growth factor (HGF) was detected at 12 h, peaked at 24 h, and returned to baseline by 72 h. c-Met/HGF receptor was detected in the airways at 6 h, before HGF in the BAL, and continued to be observed 96 h after the last OVA challenge.

CONCLUSIONS

These data identify a temporal association between growth factor production and Th2 cytokine production and the kinetics of AHR. Growth factors may play important roles in the development of allergic airway inflammation and AHR even in the early stages of asthma, before remodeling is initiated.

Nuclear and membrane receptor-mediated signalling pathways modulate polyamine biosynthesis and interconversion

Polyamines play an important role in cell growth and differentiation, while their overproduction has potentially oncogenic consequences. Polyamine homoeostasis, a critical determinant of cell fate, is precisely tuned at the level of biosynthesis, degradation and transport. The enzymes ODC (ornithine decarboxylase), AdoMetDC (S-adenosylmethionine decarboxylase) and SSAT (spermidine/spermine N(1)-acetyltransferase) are critical for polyamine pool maintenance. Our experiments were designed to examine the expression of these enzymes in testosterone-induced hypertrophic and antifolate-induced hyperplastic mouse kidney, characterized by activation of AR (androgen receptor) and HGF (hepatocyte growth factor) membrane receptor c-Met respectively. The expression of these key enzymes was up-regulated by antifolate CB 3717 injury-evoked activation of HGF/c-Met signalling. In contrast, activation of the testosterone/AR pathway remarkably induced a selective increase in ODC expression without affecting other enzymes. Studies in catecholamine-depleted kidneys point to a synergistic interaction between the signalling pathways activated via cell membrane catecholamine receptors and AR, as well as c-Met. We found that this cross-talk modulated the expression of ODC and AdoMetDC, enzymes limiting polyamine biosynthesis, but not SSAT. This is in contrast with the antagonistic cross-talk between AR- and c-Met-mediated signalling which negatively regulated the expression of ODC, but affected neither AdoMetDC nor SSAT.

Protective effects of peroxisome proliferator-activated receptor gamma ligand on apoptosis and hepatocyte growth factor induction in renal ischemia-reperfusion injury

BACKGROUND

Renal ischemia-reperfusion injury affects the long-term outcome of renal graft survival. Thiazolidinediones (TZDs), synthetic peroxisome proliferator-activated receptor (PPAR)-gamma ligands, have been shown to exert therapeutic effects upon renal ischemia-reperfusion injury far beyond their use as insulin sensitizers. It has also been reported that hepatocyte growth factor (HGF) has a beneficial effect on renal ischemia-reperfusion injury and that TZDs induce increased HGF mRNA expression and protein secretion. We investigated the effect of troglitazone, one of the TZDs, in a rat model of renal ischemia-reperfusion injury.

METHODS

A 45-minute period of warm renal ischemia was induced by bilateral clamping at 37 degrees C with rats being sacrificed before the onset of ischemia and at 2, 4, 6, and 12 hr after reperfusion. The expression of PPAR-gamma was measured by reverse-transcriptase polymerase chain reaction (RT-PCR) and western blotting while the production of HGF was investigated by RT-PCR and immunohistochemistry. The effect of troglitazone treatment on the level of apoptosis was determined by staining for cleaved caspase-3 and single-stranded DNA (ssDNA).

RESULTS

The numbers of cleaved caspase-3 and ssDNA positive cells were decreased in rats treated with troglitazone. The production of HGF mRNA and protein was most intense at 4 hr. The expression of PPAR-gamma and HGF was increased in the group treated with troglitazone compared with the control group. CONCLUSIONS.: Pretreatment of rats with the PPAR-gamma ligand troglitazone decreased apoptotic cell death in renal ischemia-reperfusion injury as a result of the induction of HGF.

HGF/SF regulates expression of apoptotic genes in MCF-10A human mammary epithelial cells

Hepatocyte growth factor/scatter factor (HGF/SF) induces scattering, morphogenesis, and survival of epithelial cells through activation of the MET tyrosine kinase receptor. HGF/SF and MET are involved in normal development and tumor progression of many tissues and organs, including the mammary gland. In order to find target genes of HGF/SF involved in its survival function, we used an oligonucleotide microarray representing 1,920 genes known to be involved in apoptosis, transcriptional regulation, and signal transduction. MCF-10A human mammary epithelial cells were grown in the absence of serum and treated or not with HGF/SF for 2 h. Total RNA was reverse-transcribed to cDNA in the presence of fluorescent Cy3-dUTP or Cy5-dUTP to generate fluorescently labeled cDNA probes. Microarrays were performed and the ratios of Cy5/Cy3 fluorescence were determined. The expression of three apoptotic genes was modified by HGF/SF, with A20 being upregulated, and DAXX and SMAC being downregulated. These changes of expression were confirmed by real-time quantitative PCR. According to current-knowledge, A20 is antiapoptotic and SMAC is proapoptotic, while a pro- or antiapoptotic function of DAXX is controversial. The fact that HGF/SF upregulates an antiapoptotic gene (A20) and downregulates a proapoptotic gene (SMAC) is in agreement with its survival effect in MCF-10A cells. This study identified novel apoptotic genes regulated by HGF/SF, which can contribute to its survival effect.

Pharmacologic treatment of acute kidney injury: why drugs haven't worked and what is on the horizon

Current strategies to limit the extent of injury in acute renal failure are based on extensive studies that identified cellular and molecular mechanisms of acute kidney injury. Despite successes in various animal models, translation to human studies has failed or studies are inconclusive. This review describes past failures and barriers to successful clinical trials. It also focuses on promising preclinical studies using novel compounds that currently are in or close to human investigation. Implementation of previous or novel compounds in well-designed clinical trials provides hope for the successful treatment of this devastating disorder.

Blocking tumor necrosis factor-α inhibits folic acid-induced acute renal failure

Systemic administration of mice with folic acid (FA) has been used for studying the pathogenesis of acute renal failure. However, the molecular mechanisms by which FA induces acute renal failure remain poorly understood. We found that CD-1 mice treated with FA developed acute renal failure characterized by increased blood urea nitrogen, necrosis, and apoptosis of tubular epithelial cells. Compared to control mice, tumor necrosis factor-alpha (TNF-alpha) was markedly elevated in blood and kidneys of these FA-treated mice, accompanied by markedly reduced expression of anti-apoptotic protein BclxL in their kidneys. In vivo administration of FA-treated CD-1 mice with neutralizing anti-TNF-alpha antibody restored the expression of BclxL in kidneys and inhibited the necrosis and apoptosis of renal tubular epithelial cells, leading to the amelioration of acute renal failure. In ex vivo cultures, we found that FA enhanced production of TNF-alpha, decreased expression of BclxL protein, and induced apoptosis of mouse cortical tubule (MCT) cells. Addition of neutralizing anti-TNF-alpha antibody, but not control IgG, in the cultures markedly blocked the apoptotic death of FA-treated MCT cells and restored expression of BclxL to the same levels as those MCT cells cultured in the absence of FA. All these results suggest that TNF-alpha is a critical inflammatory cytokine responsible for FA-mediated acute renal failure. Furthermore, in vivo administration of anti-TNF-alpha antibody may be proved as an effective approach for acute renal failure prevention and treatment.

Cell confluence regulates hepatocyte growth factor-stimulated cell morphogenesis in a beta-catenin-dependent manner

Following organ injury, morphogenic epithelial responses can vary depending on local cell density. In the present study, the role of cell confluence in determining the responsiveness of renal epithelial cells to the dedifferentiating morphogenic signals of hepatocyte growth factor (HGF) was examined. Increasing confluence resulted in a greater tendency of cells to organize into epithelial tubes and a significant decrease in migratory responsiveness to HGF. Analysis of downstream signaling revealed that the HGF receptor c-Met was equally activated in confluent and nonconfluent cells following HGF stimulation but that phosphoinositide 3-kinase-dependent activation of Akt and Rac were selectively diminished in confluent cells. In nonconfluent cells treated with HGF, the high level of Akt activation resulted in inhibitory phosphorylation of glycogen synthase kinase 3beta (GSK-3beta) and increased beta-catenin nuclear signaling. In contrast, confluent cells, in which HGF-stimulated Akt activation was diminished, displayed less inhibitory phosphorylation of GSK-3beta and less nuclear signaling by beta-catenin. Overexpression of beta-catenin (SA), which cannot be phosphorylated by GSK-3beta and targeted for ubiquitination, significantly increased migration in fully confluent cells. Thus, cells maintained at high confluence selectively downregulate signaling events such as Rac activation and beta-catenin-dependent transcription that would otherwise promote cell dedifferentiation and migration.

Acute renal failure: much more than a kidney disease

Acute renal failure is a frequent clinical problem with an increasing incidence, an unacceptably high mortality rate that has not improved in more than 40 years, and no specific treatment, yet renal failure is not the usual cause of death. The role of inflammation has been documented in both acute renal injury and cardiac dysfunction. Several investigators have shown that congestive heart failure is associated with increased mortality in patients with acute renal failure. This article reviews some of the cardiac and other distant organ effects of acute renal injury that may be important in the morbidity and mortality observed clinically. Cardiac changes after experimental renal ischemia include cytokine induction, leukocyte infiltration, cell death by apoptosis, and impaired function. I propose that the extrarenal effects of kidney injury must be considered in designing therapies. Acute renal failure has systemic consequences and must be thought of as more than a kidney disease.

The role of hepatocyte growth factor in the humoral regulation of inguinal hernia closure

BACKGROUND

Calcitonin gene-related peptide (CGRP) is proposed to indirectly cause inguinal hernia closure via hepatocyte growth factor (HGF). Studies have shown that CGRP and HGF cause processus vaginalis (PV) fusion in vitro. We localized the HGF receptor in the PV and tested whether CGRP was responsible for HGF release.

METHOD

Hernial sacs collected from 20 children (15 males, 4 females, 1 XY female) undergoing inguinal hernia repair were immunohistochemically stained for HGF receptor (c-met). Parietal peritoneum was stained for comparison. Hernial sacs from another 16 children (12 males, 4 females), with each sac divided into 4, were cultured, with and without CGRP, for 24 and 48 hours. Hepatocyte growth factor content was then assayed in the culture medium (4/16 children) and tissue extracts (12/16 children), using enzyme-linked immunosorbent assay. Children were aged 1 month to 10 years. Data were analyzed using paired Student t tests.

RESULTS

C-met localized to the PV epithelial surface in 17 of 20 hernial sacs and in the parietal peritoneum. Hepatocyte growth factor levels increased over time in 4 of 4 culture medium assays, with a significant difference in 1 of 4. Seven of 12 tissue extract assays had significant differences; however, 3 of 7 had decreased HGF levels.

CONCLUSION

The presence of HGF receptors in the PV is consistent with a role for HGF in triggering epithelial-mesenchymal transformation during inguinal hernia closure. The presence of HGF receptors in the parietal peritoneum suggests that regulation of this process is complex. Enzyme-linked immunosorbent assay results indicate that, in a subset of patients, exogenous CGRP may be responsible for HGF elevation and potentially implicates deficient endogenous CGRP as one cause for inguinal hernia patency.

Expression of a candidate marker for progenitor cells, Musashi-1, in the proliferative regions of human antrum and its decreased expression in intestinal metaplasia

AIM

Reliable makers for progenitor cells in the human stomach have not been elucidated. The aim of the present study was to clarify whether Musashi-1 (Msi-1), which has recently been proposed as a stem cell marker in mouse intestine, serves as a marker for progenitor cells in human stomach.

METHODS AND RESULTS

Immunohistochemistry revealed that Msi-1+ cells were detected especially in the isthmus/neck region (the putative position of stem cells) of the adult antrum, but were limited to the basal regions of fetal pyloric glands during the early stages of development. These results suggest that Msi-1 expression occurs specifically in the stem cell-containing regions. Msi-1+ cells were intermingled with proliferating cell nuclear antigen (PCNA)+ cells in the isthmus/neck region of the adult antrum, but did not coexpress PCNA or Ki 67. Msi-1 expression overlapped partly with expression of MUC 5 AC and MUC 6, indicating that Msi-1+ cells retain some features of both foveolar and pyloric gland cell differentiation phenotypes. In contrast, Msi-1 expression in gastric glands showing intestinal metaplasia (IM) became weaker than that in the glands without IM.

CONCLUSION

The specific expression of Msi-1 within the proliferative regions suggests that Msi-1 is a marker of cells with progenitor characteristics before active proliferation in human antrum.

VEGF induces proliferation, migration, and TGF-β1 expression in mouse glomerular endothelial cells via mitogen-activated protein kinase and phosphatidylinositol 3-kinase

The role of glomerular endothelial cells in kidney fibrosis remains incompletely understood. While endothelia are indispensable for repair of acute damage, they can produce extracellular matrix proteins and profibrogenic cytokines that promote fibrogenesis. We used a murine cell line with all features of glomerular endothelial cells (glEND.2), which dissected the effects of vascular endothelial growth factor (VEGF) on cell migration, proliferation, and profibrogenic cytokine production. VEGF dose-dependently induced glEND.2 cell migration and proliferation, accompanied by up-regulation of VEGFR-2 phosphorylation and mRNA expression. VEGF induced a profibrogenic gene expression profile, including up-regulation of TGF-beta1 mRNA, enhanced TGF-beta1 secretion, and bioactivity. VEGF-induced endothelial cell migration and TGF-beta1 induction were mediated by the phosphatidyl-inositol-3 kinase pathway, while proliferation was dependent on the Erk1/2 MAP kinase pathway. This suggests that differential modulation of glomerular angiogenesis by selective inhibition of the two identified VEGF-induced signaling pathways could be a therapeutic approach to treat kidney fibrosis.

Prevention of neutrophil extravasation by hepatocyte growth factor leads to attenuations of tubular apoptosis and renal dysfunction in mouse ischemic kidneys

Ischemia and reperfusion (I/R) injuries occur in numerous organs under pathophysiological conditions. In this process, neutrophils play important roles in eliciting parenchymal injuries. Using a murine model of renal I/R, we show that hepatocyte growth factor (HGF) is a natural ligand that inhibits endothelial injuries and neutrophil extravasation. In mice after renal I/R, plasma HGF levels increased, along with c-Met/HGF receptor phosphorylation in the vascular endothelium. However, this c-Met activation was transient, associated with a decrease in endogenous HGF level, and followed by neutrophil infiltration and renal dysfunction. Suppression of endothelial c-Met phosphorylation by anti-HGF IgG led to rapid progressions of neutrophil extravasation, tubular apoptosis, and renal dysfunction. Inversely, enhancement of the c-Met activation by exogenous HGF blocked endothelial/tubular apoptotic injuries and acute renal failure. In this process, HGF prevented endothelial nuclear factor kappaB activation and inhibited induction of an adhesion molecule (ICAM-1), resulting in attenuated vascular edema and neutrophil infiltration. Thus, we conclude that 1) the HGF/c-Met system of endothelial cells confers an initial barrier to block neutrophil infiltration, and 2) transient and insufficient HGF production allows manifestation of postischemic renal failure. Our study provides a rationale for why HGF supplementation elicits therapeutic effects in ischemic kidneys.

Direct electrotransfer of hHGF gene into kidney ameliorates ischemic acute renal failure

In the early phase of kidney transplantation, the transplanted kidney is exposed to insults like ischemia/reperfusion, which is a leading cause of acute renal failure (ARF). ARF in the context of renal transplantation predisposes the graft to developing chronic damage and to long-term graft loss. Hepatocyte growth factor (HGF) has been suggested to support the intrinsic ability of the kidney to regenerate in response to injury by its morphogenic, mitogenic, motogenic and antiapoptotic activities. In the present paper, we examine whether human HGF (hHGF) gene electrotransfer helps in the recovery from ARF in a model of rat renal warm ischemia. We also assess the advantages of this form of gene therapy by direct electroporation of the kidney, given that transplantation offers the possibility of manipulating the organ in vivo. We have compared the therapeutic efficiency of two electroporation methodologies in a rat ARF model. Although they both targeted the same organ, the two methods were applied to different parts of the animal: muscle and kidney. Kidney direct electrotransfer was shown to be more efficient not only in pharmacokinetic but also in therapeutic terms, so it may become a clinically practical alternative in renal transplantation.

Hepatocyte Growth Factor Ameliorates the Progression of Experimental Autoimmune Myocarditis

Hepatocyte growth factor (HGF) plays a role in cell protection, antiapoptosis, antifibrosis, and angiogenesis. However, the role of HGF in the immune system is not well defined. We examined the influence of HGF on T cells and the effects of HGF therapy in acute myocarditis. Lewis rats were immunized on day 0 with cardiac myosin to establish experimental autoimmune myocarditis (EAM). Human HGF gene with hemagglutinating virus of the Japan-envelope vector was injected directly into the myocardium on day 0 or on day 14 (two groups of treated rats). Rats were killed on day 21. Expression of c-Met/HGF receptor in splenocytes and myocardial infiltrating cells was confirmed by immunohistochemical staining or FACS analysis. Myocarditis-affected areas were smaller in the treated rats than in control rats. Cardiac function in the treated rats was markedly improved. An antigen-specific T cell proliferation assay was done with CD4-positive T cells isolated from control rats stimulated with cardiac myosin. HGF suppressed T cell proliferation and production of IFN-γ and increased production of IL-4 and IL-10 secreted from CD4-positive T cells in vitro. Additionally, TUNEL assay revealed that HGF reduced apoptosis in cardiomyocytes. HGF reduced the severity of EAM by inducing T helper 2 cytokines and suppressing apoptosis of cardiomyocytes. HGF has potential as a new therapy for myocarditis.

Gene therapy for renal disorders

During the last 20 years there have been major improvements in renal replacement therapy, including dialysis and kidney transplantation; however, the treatment options for renal diseases are still limited. Gene therapy is a potential modality for many renal diseases for which we are as yet unable to offer specific treatment. This article reviews the recent data on gene therapy in animal models applicable to human renal diseases and evaluates its efficacy, safety and clinical relevance. Several approaches appear to be promising, including adeno-associated viral vectors for long-term gene expression, electroporation for muscular gene delivery, ultrasound/microbubble-mediated gene targeting, macrophage-based gene therapy and small interfering RNAs.

Both Sp1 and Smad participate in mediating TGF-β1-induced HGF receptor expression in renal epithelial cells

Hepatocyte growth factor (HGF) receptor is a transmembrane receptor tyrosine kinase encoded by the c-met protooncogene. In this study, we demonstrated that c-met expression was upregulated in the kidney after obstructive injury in mice. Because the pattern of c-met induction was closely correlated with transforming growth factor-β1 (TGF-β1) expression in vivo, we further investigated the regulation of c-met expression in renal tubular epithelial (HKC) cells by TGF-β1 in vitro. Real-time RT-PCR and Northern and Western blot analyses revealed that TGF-β1 significantly induced c-met expression in HKC cells, which primarily took place at the gene transcriptional level. Overexpression of inhibitory Smad7 completely abolished c-met induction, indicating its dependence on Smad signaling. Interestingly, TGF-β1-induced c-met expression was also contingent on a functional Sp1, as ablation of Sp1 binding with mithramycin A abrogated c-met induction in HKC cells. Transfection and sequence analysis identified a cis-acting TGF-β1-responsive region in the c-met promoter, in which resided a putative Smad-binding element (SBE) and an adjacent Sp1 site. TGF-β1 not only induced Smad binding to the SBE/Sp1 sites in the c-met promoter, but also enhanced the binding of Sp proteins. Furthermore, Sp1 could form a complex with Smads in a TGF-β1-dependent fashion. These results suggest a novel regulatory mechanism controlling c-met expression by TGF-β1 in renal epithelial cells, in which both Smad and Sp proteins participate and cooperate in activating c-met gene transcription.

Rare Incorporation of Bone Marrow-Derived Cells Into Kidney After Folic Acid-Induced Injury

Results obtained in recent experiments suggest that bone marrow-derived cells (BMDCs) engraft into tissues and differentiate into various somatic cell types. However, it is unclear whether injury is required for the phenomenon to occur at appreciable frequencies. In this study we tested whether BMDCs engraft into kidneys and differentiate into renal cells in the absence or presence of toxic injury. Renal damage was induced by delivery of folic acid (FA) to bone marrow (BM)-recipient mice 1 or 9 months after bone marrow transplant, and kidneys were examined for donor-derived cells 2,4, or 8 weeks after injury. Donor-derived cells were abundant in the renal interstitium of injured kidneys and were detected in glomeruli of vehicle- and FA-treated mice. Most of these cells expressed the common leukocyte antigen CD45 and display morphological characteristics of white blood cells. No donor-derived renal tubule cells (RTCs) were detected in kidney sections of BM-recipient mice. However, in cell culture, a cluster of seven donor-derived cells of 4 x 10(6) RTCs examined (approximately 0.0002%) displayed morphological characteristics of RTCs. CD45+ cells of donor origin were also detected in glomeruli and glomerular outgrowths. Nested polymerase chain reaction analysis for the male-specific Sry gene in cultured RTCs and glomerular outgrowths confirmed the presence of donor-derived cells. These results suggest that BMDCs may incorporate into glomeruli as specialized glomerular mesangial cells; however, BMDCs rarely contribute to the repair of renal tubules in uninjured or FA-treated mouse kidneys.

Expression of Mediators of Renal Injury in the Remnant Kidney of ROP Mice Is Attenuated by Cyclooxygenase-2 Inhibition

To investigate the effects of cyclooxygenase-2 (COX-2) inhibition on renal injury of mice, ROP mice were subjected to subtotal ablation ('remnant'). A subset of the remnant group was treated with a selective COX-2 inhibitor, SC58236, in the drinking water. At 12 weeks the remnant group developed significant albuminuria (181.3 +/- 15.8 microg/24 h), which was blunted by SC58236 treatment (138.9 +/- 17.1; p < 0.05 compared to remnant). SC58236 did not alter systemic blood pressure or GFR significantly. Immunoreactive COX-2 was upregulated in remnant (1.88 +/- 0.35 fold sham, n = 8, p < 0.05), which was blunted by SC58236 (to 1.26 +/- 0.31 fold sham). Collagen IV mRNA increased significantly in remnant kidneys (2.69 +/- 0.34 fold sham, n = 8, p < 0.05), and this increase was inhibited by SC58236 treatment (to 1.84 +/- 0.32 fold control). Immunoreactive TGF-beta1, connective tissue growth factor, HGF receptor, c-Met, and fibronectin all increased in remnant (2.85 +/- 0.51, 3.83 +/- 0.55, 2.56 +/- 0.31, and 2.80 +/- 0.39 fold sham respectively, n = 4-8, p < 0.05), and SC58236 blunted the increases (to 1.45 +/- 0.34, 1.85 +/- 0.13, 1.75 +/- 0.30, and 1.60 +/- 0.32 fold sham). Immunohistochemistry indicated that the major localization for these progression factors was in the tubulointerstitium, especially in the scar area, which is in agreement with the expression of a macrophage marker, F4/80. Therefore, these results indicate that in a mouse model of subtotal renal ablation, COX-2 inhibition blocks expression of mediators of renal tubulointerstitial injury.

Hepatocyte growth factor attenuates airway hyperresponsiveness, inflammation, and remodeling

Hepatocyte growth factor (HGF) is known to influence a number of cell types and their production of regulatory cytokines. We investigated the potential of recombinant HGF to regulate not only the development of allergic airway inflammation and airway hyperresponsiveness (AHR), but also airway remodeling in a murine model. Administration of exogenous HGF after sensitization but during ovalbumin challenge significantly prevented AHR, as well as eosinophil and lymphocyte accumulation in the airways; interleukin (IL)-4, IL-5, and IL-13 levels in bronchoalveolar lavage (BAL) fluid were also significantly reduced. Further, treatment with HGF significantly suppressed transforming growth factor-beta (TGF-beta), platelet-derived growth factor, and nerve growth factor levels in BAL fluid. The expression of TGF-beta, the development of goblet cell hyperplasia and subepithelial collagenization, and the increases in contractile elements in the lung were also reduced by recombinant HGF. Neutralization of endogenous HGF resulted in increased AHR as well as the number of eosinophils, levels of Th2 cytokines (IL-4, IL-5, and IL-13) and TGF-beta in BAL fluid. These data indicate that HGF may play an important role in the regulation of allergic airway inflammation, hyperresponsiveness, and remodeling.