Activation of Src kinase in platelet-derived growth factor-B-dependent tubular regeneration after acute ischemic renal injury

Effect of Tyrosine Kinase Inhibitor Therapy on Estimated Glomerular Filtration Rate in Patients with Chronic Myeloid Leukemia

INTRODUCTION

The advent of tyrosine kinase inhibitors (TKIs) was revolutionary in the management of chronic myeloid leukemia (CML). Although TKIs were generally considered to be safe, they can be associated with renal injury. We evaluated the effect of TKIs on renal functions in a cohort of patients with long-term follow-up.

MATERIAL AND METHODS

We retrospectively examined patients with chronic phase CML treated with TKIs. We analyzed the estimated glomerular filtration rate (eGFR) of patients from the initiation of TKI to the last follow-up. eGFR values of CML patients were compared to those of patients with stage 1 or 2 chronic kidney disease (CKD).

RESULTS

A total of 195 patients with CML and 138 patients with CKD were examined. eGFR decline was 1.556 ml/min/1.73m2/year for patients with CML (P = .221). Patients receiving second-generation TKIs (2GTKI) were estimated to have 0.583 ml/min/1.73m2 higher eGFR value than that of the imatinib group, but it was not significant (P = .871). eGFR of patients who had used bosutinib had a downward trend. Duration of TKI therapy, age, and hypertension were found to be significant factors in eGFR decline for CML patients. Lower baseline GFR was associated with an increased risk of CKD development.

CONCLUSION

Imatinib could result in a decline in eGFR which was clinically similar to early-stage CKD patients. We did not observe significant kidney function deterioration in patients receiving 2GTKIs including dasatinib and nilotinib. We recommend close renal function monitoring in patients receiving imatinib, especially for elderly patients with lower baseline eGFR and hypertension.

Case Report of Renal Calculi in a Child Receiving Imatinib for Acute Lymphoblastic Leukemia

Rationale

Imatinib is used in the treatment of Philadelphia chromosome positive (Ph+) leukemias and has been reported to have a direct effect on bone physiology.

Presentation

To report on a child with Ph+ acute lymphoblastic leukemia who presented with bilateral flank pain and gross hematuria.

Diagnosis

She was diagnosed with obstructive kidney stones 101 days after commencing daily oral imatinib. Stone analysis revealed the presence of calcium phosphate.

Interventions and outcome

The patient passed the stones spontaneously with medical therapy that included the use of thiazide, allopurinol, and potassium citrate, but she required temporary insertion of a double-J stent to relieve an obstruction.

Novel findings

Imatinib inhibits receptor tyrosine kinases and stimulates the flux of calcium from the extracellular fluid into bone, resulting in hypocalcemia with a compensatory rise in parathyroid hormone that may result in phosphaturia and the formation of calcium phosphate stones. Given that kidney stones are rare events in children, we believe that monitoring for kidney stone formation needs to be performed in children receiving imatinib.

Renal Safety Profile of BCR-ABL Tyrosine Kinase Inhibitors in a Real-Life Setting: A Study Based on Vigibase®, the WHO Pharmacovigilance Database

Background: Alongside their BCR-ABL specificity, TKIs used in chronic myeloid leukemia also target other tyrosine kinases expressed in the kidney such as PDGFR, c-KIT, SRC, and VEGFR, which may result in specific renal adverse drug reaction (ADR). To evaluate the renal safety profile in real-life conditions, a case/non-case study was performed on VigiBase®, the WHO global safety database. Methods: From 7 November 2001 to 2 June 2021, all cases in which the involvement of imatinib, dasatinib, nilotinib, bosutinib, and ponatinib was suspected in the occurrence of renal ADR were extracted from VigiBase®. Disproportionality analyses were assessed using the reporting odds ratio. Results: A total of 1409 cases were included. Imatinib accounts for half of the reported cases. A signal of disproportionate reporting (SDR) of renal failure and fluid retention was found for the five TKIs. Only dasatinib and nilotinib were related to an SDR for nephrotic syndrome. Nilotinib and ponatinib were related to an SDR for renal artery stenosis, while dasatinib was related to an SDR for thrombotic microangiopathy. No SDR for tubulointerstitial nephritis was observed. Conclusion: This study identified a new safety signal, nephrotic syndrome, for nilotinib and highlights the importance of post-marketing safety surveillance.

Thrombotic Microangiopathy, Podocytopathy, and Damage to the Renal Tubules with Severe Proteinuria and Acute Renal Dysfunction Induced by Lenvatinib

Lenvatinib, a tyrosine kinase inhibitor (TKI), is a stronger inhibitor of vascular endothelial growth factor receptor, fibroblast growth factor receptors 1 to 4, and platelet-derived growth factor receptor (PDGFR) than other TKIs. We herein report a 77-year-old Japanese woman who received the minimum dose of lenvatinib for treatment of hepatocellular carcinoma. Within one month of starting treatment, she developed severe proteinuria, hypertension, and renal dysfunction. A kidney biopsy showed drug-induced thrombotic microangiopathy, podocytopathy, and polar vasculosis. We also observed damage to the renal tubules, where PDGFR is located. To our knowledge, this is the first report of lenvatinib-induced damage to the renal tubules.

Neonatal nephron loss during active nephrogenesis results in altered expression of renal developmental genes and markers of kidney injury

Preterm neonates are at a high risk for nephron loss under adverse clinical conditions. Renal damage potentially collides with postnatal nephrogenesis. Recent animal studies suggest that nephron loss within this vulnerable phase leads to renal damage later in life. Nephrogenic pathways are commonly reactivated after kidney injury supporting renal regeneration. We hypothesized that nephron loss during nephrogenesis affects renal development, which, in turn, impairs tissue repair after secondary injury. Neonates prior to 36 wk of gestation show an active nephrogenesis. In rats, nephrogenesis is ongoing until day 10 after birth. Mimicking the situation of severe nephron loss during nephrogenesis, male pups were uninephrectomized at day 1 of life (UNXd1). A second group of males was uninephrectomized at postnatal day 14 (UNXd14), after terminated nephrogenesis. Age-matched controls were sham operated. Three days after uninephrectomy transcriptional changes in the right kidney were analyzed by RNA-sequencing, followed by functional pathway analysis. In UNXd1, 1,182 genes were differentially regulated, but only 143 genes showed a regulation both in UNXd1 and UNXd14. The functional groups "renal development" and "kidney injury" were among the most differentially regulated groups and revealed distinctive alterations. Reduced expression of candidate genes concerning renal development (Bmp7, Gdnf, Pdgf-B, Wt1) and injury (nephrin, podocin, Tgf-β1) were detected. The downregulation of Bmp7 and Gdnf persisted until day 28. In UNXd14, Six2 was upregulated and Pax2 was downregulated. We conclude that nephron loss during nephrogenesis affects renal development and induces a specific regulation of genes that might hinder tissue repair after secondary kidney injury.

SLURP-1 Controls Growth and Migration of Lung Adenocarcinoma Cells, Forming a Complex With α7-nAChR and PDGFR/EGFR Heterodimer

Secreted Ly6/uPAR-related protein 1 (SLURP-1) is a secreted Ly6/uPAR protein that negatively modulates the nicotinic acetylcholine receptor of α7 type (α7-nAChR), participating in control of cancer cell growth. Previously we showed, that a recombinant analogue of human SLURP-1 (rSLURP-1) diminishes the lung adenocarcinoma A549 cell proliferation and abolishes the nicotine-induced growth stimulation. Here, using multiplex immunoassay, we demonstrated a decrease in PTEN and mammalian target of rapamycin (mTOR) kinase phosphorylation in A549 cells upon the rSLURP-1 treatment pointing on down-regulation of the PI3K/AKT/mTOR signaling pathway. Decreased phosphorylation of the platelet-derived growth factor receptor type β (PDGFRβ) and arrest of the A549 cell cycle in the S and G2/M phases without apoptosis induction was also observed. Using a scratch migration assay, inhibition of A549 cell migration under the rSLURP-1 treatment was found. Affinity extraction demonstrated that rSLURP-1 in A549 cells forms a complex not only with α7-nAChR, but also with PDGFRα and epidermal growth factor receptor (EGFR), which are known to be involved in regulation of cancer cell growth and migration and are able to form a heterodimer. Knock-down of the genes encoding α7-nAChR, PDGFRα, and EGFR confirmed the involvement of these receptors in the anti-migration effect of SLURP-1. Thus, SLURP-1 can target the α7-nAChR complexes with PDGFRα and EGFR in the membrane of epithelial cells. Using chimeric proteins with grafted SLURP-1 loops we demonstrated that loop I is the principal active site responsible for the SLURP-1 interaction with α7-nAChR and its antiproliferative effect. Synthetic peptide mimicking the loop I cyclized by a disulfide bond inhibited ACh-evoked current at α7-nAChR, as well as A549 cell proliferation and migration. This synthetic peptide represents a promising prototype of new antitumor drug with the properties close to that of the native SLURP-1 protein.

Inhibition of Src Family Kinases Ameliorates LPS-Induced Acute Kidney Injury and Mitochondrial Dysfunction in Mice

Acute kidney injury (AKI), a critical syndrome characterized by a rapid decrease of kidney function, is a global health problem. Src family kinases (SFK) are proto-oncogenes that regulate diverse biological functions including mitochondrial function. Since mitochondrial dysfunction plays an important role in the development of AKI, and since unbalanced SFK activity causes mitochondrial dysfunction, the present study examined the role of SFK in AKI. Lipopolysaccharides (LPS) inhibited mitochondrial biogenesis and upregulated the expression of NGAL, a marker of tubular epithelial cell injury, in mouse proximal tubular epithelial (mProx) cells. These alterations were prevented by PP2, a pan SFK inhibitor. Importantly, PP2 pretreatment significantly ameliorated LPS-induced loss of kidney function and injury including inflammation and oxidative stress. The attenuation of LPS-induced AKI by PP2 was accompanied by the maintenance of mitochondrial biogenesis. LPS upregulated SFK, especially Fyn and Src, in mouse kidney as well as in mProx cells. These data suggest that Fyn and Src kinases are involved in the pathogenesis of LPS-induced AKI, and that inhibition of Fyn and Src kinases may have a potential therapeutic effect, possibly via improving mitochondrial biogenesis.

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.

Proliferative signaling by ERBB proteins and RAF/MEK/ERK effectors in polycystic kidney disease

A primary pathological feature of polycystic kidney disease (PKD) is the hyperproliferation of epithelial cells in renal tubules, resulting in formation of fluid-filled cysts. The proliferative aspects of the two major forms of PKD-autosomal dominant PKD (ADPKD), which arises from mutations in the polycystins PKD1 and PKD2, and autosomal recessive PKD (ARPKD), which arises from mutations in PKHD1-has encouraged investigation into protein components of the core cell proliferative machinery as potential drivers of PKD pathogenesis. In this review, we examine the role of signaling by ERBB proteins and their effectors, with a primary focus on ADPKD. The ERBB family of receptor tyrosine kinases (EGFR/ERBB1, HER2/ERBB2, ERBB3, and ERBB4) are activated by extracellular ligands, inducing multiple pro-growth signaling cascades; among these, activation of signaling through the RAS GTPase, and the RAF, MEK1/2, and ERK1/2 kinases enhance cell proliferation and restrict apoptosis during renal tubuloepithelial cyst formation. Characteristics of PKD include overexpression and mislocalization of the ERBB receptors and ligands, leading to enhanced activation and increased activity of downstream signaling proteins. The altered regulation of ERBBs and their effectors in PKD is influenced by enhanced activity of SRC kinase, which is promoted by the loss of cytoplasmic Ca²⁺ and an increase in cAMP-dependent PKA kinase activity that stimulates CFTR, driving the secretory phenotype of ADPKD. We discuss the interplay between ERBB/SRC signaling, and polycystins and their depending signaling, with emphasis on thes changes that affect cell proliferation in cyst expansion, as well as the inflammation-associated fibrogenesis, which characterizes progressive disease. We summarize the current progress of preclinical and clinical trials directed at inhibiting this signaling axis, and discuss potential future strategies that may be productive for controlling PKD.

Renal dysfunction and anemia associated with long-term imatinib treatment in patients with chronic myelogenous leukemia

Knowledge of the toxicity profile of long-term treatment with imatinib is limited. In the present study, we sought to evaluate renal function and hemoglobin levels during long-term imatinib treatment. Eighty-two patients with chronic myelogenous leukemia in chronic phase who had been on imatinib for over 5 years were retrospectively analyzed. The mean estimated glomerular filtration rate (eGFR) was significantly decreased over 5 years (77 ± 17 to 62 ± 14 ml/min/1.73m², P < 0.001). Higher age and lower eGFR value at initiation of imatinib were significantly associated with development of renal dysfunction by multivariate analyses. Mean hemoglobin levels also significantly decreased over the 5-year period (12.9 ± 1.7 to 12.4 ± 1.3 g/dl, P < 0.01). The rate of decrease in eGFR correlated significantly with hemoglobin levels (correlation coefficient = - 0.249, P < 0.05). Serum erythropoietin (EPO) levels did not increase in 16 patients with both renal dysfunction and anemia (median, 31.9 mIU/ml). In patients who participated in a clinical trial of imatinib discontinuation, mean eGFR (50.0 ± 6.5 to 56.0 ± 10.2 ml/min/1.73m², P < 0.05) and hemoglobin levels (12.0 ± 1.7 to 14.0 ± 1.6 g/dl, P < 0.01) improved significantly at 1 year after discontinuation. These findings suggest that long-term imatinib results in a partially reversible continuous decline in renal function and decreased hemoglobin levels.

A small molecule fibrokinase inhibitor in a model of fibropolycystic hepatorenal disease

AIM

To evaluate the novel platelet-derived growth factor receptor and vascular endothelial growth factor receptor dual kinase inhibitor ANG3070 in a polycystic kidney disease-congenital hepatic fibrosis model.

METHODS

At 6 wk of age, PCK rats were randomized to vehicle or ANG3070 for 4 wk. At 10 wk, 24 h urine and left kidneys were collected and rats were continued on treatment for 4 wk. At 14 wk, 24 h urine was collected, rats were sacrificed, and liver and right kidneys were collected for histological evaluation. For Western blot studies, PCK rats were treated with vehicle or ANG3070 for 7 d and sacrificed approximately 30 min after the last treatments.

RESULTS

Compared to the wild-type cohort, the PCK kidney (Vehicle cohort) exhibited a marked increase in kidney and liver mass, hepato-renal cystic volume, hepato-renal fibrosis and hepato-renal injury biomarkers. Intervention with ANG3070 in PCK rats decreased kidney weight, reduced renal cystic volume and reduced total kidney hydroxyproline, indicating significantly reduced rental interstitial fibrosis compared to the PCK-Vehicle cohort. ANG3070 treatment also mitigated several markers of kidney injury, including urinary neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, cystatin C and interleukin-18 levels. In addition, this treatment attenuated key indices of renal dysfunction, including proteinuria, albuminuria and serum blood urea nitrogen and creatinine, and significantly improved renal function compared to the PCK-Vehicle cohort. ANG3070 treatment also significantly decreased liver enlargement, hepatic lesions, and liver fibrosis, and mitigated liver dysfunction compared to the PCK-Vehicle cohort.

CONCLUSION

These results suggest that ANG3070 has the potential to slow disease, and may serve as a bridge toward hepato-renal transplantation in patients with fibropolycystic disease.

Pharmacological inhibition of Src kinase protects against acute kidney injury in a murine model of renal ischemia/reperfusion

Activation of Src kinase has been implicated in the pathogenesis of acute brain, liver, and lung injury. However, the role of Src in acute kidney injury (AKI) remains unestablished. To address this, we evaluated the effects of Src inhibition on renal dysfunction and pathological changes in a murine model of AKI induced by ischemia/reperfusion (I/R). I/R injury to the kidney resulted in increased Src phosphorylation at tyrosine 416 (activation). Administration of PP1, a highly selective Src inhibitor, blocked Src phosphorylation, improved renal function and ameliorated renal pathological damage. PP1 treatment also suppressed renal expression of neutrophil gelatinase-associated lipocalin and reduced apoptosis in the injured kidney. Moreover, Src inhibition prevented downregulation of several adherens and tight junction proteins, including E-cadherin, ZO-1, and claudins-1/−4 in the kidney after I/R injury as well as in cultured renal proximal tubular cells following oxidative stress. Finally, PP1 inhibited I/R–induced renal expression of matrix metalloproteinase-2 and -9, phosphorylation of extracellular signal–regulated kinases1/2, signal transducer and activator of transcription-3, and nuclear factor-κB, and the infiltration of macrophages into the kidney. These data indicate that Src is a pivotal mediator of renal epithelial injury and that its inhibition may have a therapeutic potential to treat AKI.

Phosphatidylinositol 3-Kinase-DNA Methyltransferase 1-miR-1281-Histone Deacetylase 4 Regulatory Axis Mediates Platelet-Derived Growth Factor-Induced Proliferation and Migration of Pulmonary Artery Smooth Muscle Cells

BACKGROUND

Platelet-derived growth factor BB, a potent mitogen of pulmonary artery smooth muscle cells (PASMCs), has been implicated in pulmonary arterial remodeling, which is a key pathogenic feature of pulmonary arterial hypertension. Previous microRNA profiling in platelet-derived growth factor BB-treated PASMCs found a significantly downregulated microRNA, miR-1281, but it has not been associated with any cellular function, and we investigated the possibility.

METHODS AND RESULTS

Real-time quantitative reverse transcription-polymerase chain reaction assay proved that downregulation of miR-1281 was a conserved phenomenon in human and rat PASMCs. Overexpression and inhibition of miR-1281 in PASMCs promoted and suppressed, respectively, the cell proliferation and migration. Bioinformatic prediction and 3'-untranslated region reporter assay identified histone deacetylase 4 to be a direct target of miR-1281. Supporting this, proliferation and migration assay demonstrated the cellular function of histone deacetylase 4 is inversely correlated with that of miR-1281. Mechanistically, it is found that platelet-derived growth factor BB activates the phosphatidylinositol 3-kinase pathway, which then induces the expression of DNA methyltransferase 1, leading to enhanced methylation of a flanking CpG island and repressed miR-1281 expression. Finally, a reduced miR-1281 level was consistently identified in hypoxic PASMCs in vitro, in pulmonary arteries of rats with monocrotaline-induced pulmonary arterial hypertension, and in serum of patients with coronary heart disease-pulmonary arterial hypertension. These data suggest that there may be a diagnostic and therapeutic use for miR-1281.

CONCLUSIONS

Herein, we report a novel regulatory axis, phosphatidylinositol 3-kinase-DNA methyltransferase 1-miR-1281-histone deacetylase 4, integrating multiple epigenetic regulators that participate in platelet-derived growth factor BB-stimulated PASMC proliferation and migration and pulmonary vascular remodeling.

Molecular Regulation of Sprouting Angiogenesis

The term angiogenesis arose in the 18th century. Several studies over the next 100 years laid the groundwork for initial studies performed by the Folkman laboratory, which were at first met with some opposition. Once overcome, the angiogenesis field has flourished due to studies on tumor angiogenesis and various developmental models that can be genetically manipulated, including mice and zebrafish. In addition, new discoveries have been aided by the ability to isolate primary endothelial cells, which has allowed dissection of various steps within angiogenesis. This review will summarize the molecular events that control angiogenesis downstream of biochemical factors such as growth factors, cytokines, chemokines, hypoxia-inducible factors (HIFs), and lipids. These and other stimuli have been linked to regulation of junctional molecules and cell surface receptors. In addition, the contribution of cytoskeletal elements and regulatory proteins has revealed an intricate role for mobilization of actin, microtubules, and intermediate filaments in response to cues that activate the endothelium. Activating stimuli also affect various focal adhesion proteins, scaffold proteins, intracellular kinases, and second messengers. Finally, metalloproteinases, which facilitate matrix degradation and the formation of new blood vessels, are discussed, along with our knowledge of crosstalk between the various subclasses of these molecules throughout the text. Compr Physiol 8:153-235, 2018.

Inflammation and renal fibrosis: Recent developments on key signaling molecules as potential therapeutic targets

Chronic kidney disease (CKD) is a major public health issue. At the histological level, renal fibrosis is the final common pathway of progressive kidney disease irrespective of the initial injury. Considerable evidence now indicates that renal inflammation plays a central role in the initiation and progression of CKD. Some of the inflammatory signaling molecules involved in CKD include: monocyte chemoattractant protein-1 (MCP-1), bradykinin B₁ receptor (B₁R), nuclear factor κB (NF-κB), tumor necrosis factor-α (TNFα), transforming growth factor β (TGF-β), and platelet-derived growth factor (PDGF). Multiple antifibrotic factors, such as interleukin-10 (IL-10), interferon-γ (IFN-γ), bone morphogenetic protein-7 (BMP-7), hepatocyte growth factor (HGF) are also downregulated in CKD. Therefore, restoration of the proper balance between pro- and antifibrotic signaling pathways could serve as a guiding principle for the design of new antifibrotic strategies that simultaneously target many pathways. The purpose of this review is to summarize the existing body of knowledge regarding activation of cytokine pathways and infiltration of inflammatory cells as a starting point for developing novel antifibrotic therapies to prevent progression of CKD.

Effects of Bosutinib Treatment on Renal Function in Patients With Philadelphia Chromosome-Positive Leukemias

BACKGROUND

The purpose of the study was to assess renal function in patients with Philadelphia chromosome-positive leukemias receiving bosutinib or imatinib.

PATIENTS AND METHODS

Patients received first-line bosutinib (n = 248) or imatinib (n = 251; phase III trial), or second-line or later bosutinib (phase I/II trial; n = 570). Adverse events (AEs) and changes from baseline in estimated glomerular filtration rate (eGFR) and serum creatinine were assessed.

RESULTS

Time from the last patient's first dose to data cutoff was ≥ 48 months. Renal AEs were reported in 73/570 patients (13%) receiving second-line or later bosutinib, and in 22/248 (9%) and 16/251 (6%) receiving first-line bosutinib and imatinib, respectively. eGFR in patients receiving bosutinib declined over time with more patients developing Grade ≥ 3b eGFR (< 45 mL/min/1.73 m² according to the Modification of Diet in Renal Disease method) with second-line or later bosutinib (139/570, 24%) compared with first-line bosutinib (26/248, 10%) and imatinib (25/251, 10%); time to Grade ≥ 3b eGFR was shortest with second-line or later bosutinib. Similar proportions of patients receiving second-line or later bosutinib (74/139, 53%), first-line bosutinib (15/26, 58%), and first-line imatinib (15/25, 60%) improved to ≥ 45 mL/min/1.73 m² eGFR as of the last follow-up. In a regression analysis, first-line treatment with bosutinib versus imatinib was not a significant predictor of Grade ≥ 3b eGFR.

CONCLUSION

Long-term bosutinib treatment is associated with an apparently reversible decline in renal function with frequency and characteristics similar to renal decline observed with long-term imatinib treatment. Patients with risk factors for Grade ≥ 3b eGFR should be monitored closely.

BMP4 inhibits PDGF-induced proliferation and collagen synthesis via PKA-mediated inhibition of calpain-2 in pulmonary artery smooth muscle cells

In the present study, we investigated the effect of bone morphogenetic protein 4 (BMP4) on PDGF-induced cell proliferation and collagen synthesis in pulmonary artery smooth muscle cells (PASMCs). Normal human PASMCs were incubated with and without PDGF-BB in the absence and presence of BMP4 for 0.5 to 24 h. The protein levels of collagen-I, p-Smad2/3, p-Smad1/5, and intracellular active TGF-β1, calpain activity, and cell proliferation were then measured. The results showed that BMP4 induced an increase in p-Smad1/5 but had no effect on the protein levels of collagen-I, p-Smad2/3, and intracellular active TGF-β1 and calpain activity in control PASMCs. Nevertheless, BMP4 attenuated increases in cell proliferation and protein levels of collagen-I, p-Smad2/3, and intracellular active TGF-β1 and calpain activity in PASMCs exposed to PDGF-BB. Moreover, BMP4 increased PKA activity and inhibition of PKA prevented the inhibitory effects of BMP4 on PDGF-BB-induced calpain activation in normal PASMCs. The PKA activator forskolin recapitulated the suppressive effect of BMP4 on PDGF-induced calpain activation. Furthermore, BMP4 prevented a PDGF-induced decrease in calpain-2 phosphorylation at serine-369 in normal PASMCs. Finally, BMP4 did not attenuate PDGF-induced increases in cell proliferation, collagen-I protein levels, and calpain activation and did not induce PKA activation and did not prevent a PDGF-induced decrease in calpain-2 phosphorylation at serine-369 in PASMCs from idiopathic pulmonary arterial hypertension (PAH) patients. These data demonstrate that BMP4 inhibits PDGF-induced cell proliferation and collagen synthesis via PKA-mediated inhibition of calpain-2 in normal PASMCs. The inhibitory effects of BMP4 on PDGF-induced cell proliferation, collagen synthesis, and calpain-2 activation are impaired in PASMCs from PAH patients, which may contribute to pulmonary vascular remodeling in PAH.

Renal Toxicities of Targeted Therapies

With the incorporation of targeted therapies in routine cancer therapy, it is imperative that the array of toxicities associated with these agents be well-recognized and managed, especially since these toxicities are distinct from those seen with conventional cytotoxic agents. This review will focus on these renal toxicities from commonly used targeted agents. This review discusses the mechanisms of these side effects and management strategies. Anti-vascular endothelial growth factor (VEGF) agents including the monoclonal antibody bevacizumab, aflibercept (VEGF trap), and anti-VEGF receptor (VEGFR) tyrosine kinase inhibitors (TKIs) all cause hypertension, whereas some of them result in proteinuria. Monoclonal antibodies against the human epidermal growth factor receptor (HER) family of receptors, such as cetuximab and panitumumab, cause electrolyte imbalances including hypomagnesemia and hypokalemia due to the direct nephrotoxic effect of the drug on renal tubules. Cetuximab may also result in renal tubular acidosis. The TKIs, imatinib and dasatinib, can result in acute or chronic renal failure. Rituximab, an anti-CD20 monoclonal antibody, can cause acute renal failure following initiation of therapy because of the onset of acute tumor lysis syndrome. Everolimus, a mammalian target of rapamycin (mTOR) inhibitor, can result in proteinuria. Discerning the renal adverse effects resulting from these agents is essential for safe treatment strategies, particularly in those with pre-existing renal disease.

Adverse Renal Effects of Novel Molecular Oncologic Targeted Therapies: A Narrative Review

Novel targeted anti-cancer therapies have resulted in improvement in patient survival compared to standard chemotherapy. Renal toxicities of targeted agents are increasingly being recognized. The incidence, severity, and pattern of renal toxicities may vary according to the respective target of the drug. Here we review the adverse renal effects associated with a selection of currently approved targeted cancer therapies, directed to EGFR, HER2, BRAF, MEK, ALK, PD1/PDL1, CTLA-4, and novel agents targeted to VEGF/R and TKIs. In summary, electrolyte disorders, renal impairment and hypertension are the most commonly reported events. Of the novel targeted agents, ipilumumab and cetuximab have the most nephrotoxic events reported. The early diagnosis and prompt recognition of these renal adverse events are essential for the general nephrologist taking care of these patients.

Changes from imatinib mesylate to second generation tyrosine kinase inhibitors improve renal impairment with imatinib mesylate in chronic myelogenous leukemia

Understanding adverse events in long-term tyrosine kinase inhibitor (TKI) therapy for chronic myelogenous leukemia (CML) is important. We investigated changes in renal function during TKI therapy for CML. We retrospectively analyzed levels of serum creatinine (sCrn) and values of estimated glomerular filtration rate (eGFR) from June 2001 to March 2015. Sixty patients initially treated with imatinib were enrolled in this study. Continuous variables of sCrn and eGFR were compared by paired student's t test. Median age or duration of treatment with imatinib was 49 years (range 19-81) or 101 months (range 8-165), respectively. Mean levels of sCrn or mean values of eGFR had increased or decreased 1 year later from start of imatinib throughout observation with statistical significance (p < 0.05), respectively. In 38 patients, the TKI used was changed from imatinib to a second-generation TKI (nilotinib: 32; dasatinib: 6) for various reasons. We observed statistically significant (p < 0.05) amelioration in mean levels of sCrn and values of eGFR after only 1 month following the changes to second-generation TKIs. These results suggest that imatinib has adverse effects on renal function and that changes from imatinib to a second-generation TKI should be considered as a therapeutic option in cases of renal impairment due to imatinib.

Estimated glomerular filtration rate changes in patients with chronic myeloid leukemia treated with tyrosine kinase inhibitors

BACKGROUND

Chronic use of tyrosine kinase inhibitors (TKIs) may lead to previously unrecognized adverse events. This study evaluated the incidence of acute kidney injury (AKI) and chronic kidney disease (CKD) in chronic-phase (CP) chronic myeloid leukemia (CML) patients treated with imatinib, dasatinib, and nilotinib.

METHODS

Four hundred sixty-eight newly diagnosed CP CML patients treated with TKIs were analyzed. The molecular and cytogenetic response data, creatinine, and glomerular filtration rate (GFR) were followed from the start of therapy to the last follow-up (median, 52 months). GFR was estimated with the Modification of Diet in Renal Disease equation.

RESULTS

Nineteen patients (4%) had TKI-associated AKI. Imatinib was associated with a higher incidence of AKI in comparison with dasatinib and nilotinib (P = .014). Fifty-eight patients (14%) developed CKD while they were receiving a TKI; 49 of these patients (84%) did so while they were being treated with imatinib (P < .001). Besides imatinib, age, a history of hypertension, and diabetes mellitus were also associated with the development of CKD. In patients with no CKD at the baseline, imatinib was shown to reduce GFR over time. Interestingly, imatinib did not cause a significant decline in the GFRs of patients with a history of CKD. Imatinib, dasatinib, and nilotinib increased the mean GFR after 3 months of treatment, and nilotinib led with the most significant increase (P < .001). AKI or CKD had no significant impact on overall cytogenetic and molecular response rates or survival.

CONCLUSIONS

The administration of TKIs may be safe in the setting of CKD in CP CML patients, but close monitoring is still warranted.

The cleaved cytoplasmic tail of polycystin-1 regulates Src-dependent STAT3 activation

Polycystin-1 (PC1) mutations result in proliferative renal cyst growth and progression to renal failure in autosomal dominant polycystic kidney disease (ADPKD). The transcription factor STAT3 (signal transducer and activator of transcription 3) was shown to be activated in cyst-lining cells in ADPKD and PKD mouse models and may drive renal cyst growth, but the mechanisms leading to persistent STAT3 activation are unknown. A proteolytic fragment of PC1 corresponding to the cytoplasmic tail, PC1-p30, is overexpressed in ADPKD. Here, we show that PC1-p30 interacts with the nonreceptor tyrosine kinase Src, resulting in Src-dependent activation of STAT3 by tyrosine phosphorylation. The PC1-p30-mediated activation of Src/STAT3 was independent of JAK family kinases and insensitive to the STAT3 inhibitor suppressor of cytokine signaling 3. Signaling by the EGF receptor (EGFR) or cAMP amplified the activation of Src/STAT3 by PC1-p30. Expression of PC1-p30 changed the cellular response to cAMP signaling. In the absence of PC1-p30, cAMP dampened EGFR- or IL-6-dependent activation of STAT3; in the presence of PC1-p30, cAMP amplified Src-dependent activation of STAT3. In the polycystic kidney (PCK) rat model, activation of STAT3 in renal cystic cells depended on vasopressin receptor 2 (V2R) signaling, which increased cAMP levels. Genetic inhibition of vasopressin expression or treatment with a pharmacologic V2R inhibitor strongly suppressed STAT3 activation and reduced renal cyst growth. These results suggest that PC1, via its cleaved cytoplasmic tail, integrates signaling inputs from EGFR and cAMP, resulting in Src-dependent activation of STAT3 and a proliferative response.

Rapid nongenomic action of aldosterone on protein expressions of Hsp90( α and β ) and pc-Src in rat kidney

Previous in vitro studies indicated that aldosterone nongenomically phosphorylates epidermal growth factor receptor (EGFR) through activation of upstream signals, heat shock protein 90 β (Hsp90 β ), and cytosolic (c)-Src kinase. We demonstrated that aldosterone rapidly elevates EGFR phosphorylation in rat kidney. There are no in vivo data regarding renal Hsp90( α and β ) and phosphorylated (p)c-Src protein expressions. The present study further investigates the expressions of these proteins. Male Wistar rats were intraperitoneally injected with normal saline solution or aldosterone (Aldo: 150 μ g/kg BW). After 30 minutes, abundances and localizations of these proteins were determined. Aldosterone enhanced renal Hsp90 β protein abundance (P < 0.001), but Hsp90 α and pc-Src protein levels remained unaltered. Expression of Hsp90( α and β ) was induced prominently in the proximal convoluted tubules (PCTs). Activation of Hsp90 α was observed in vascular and outer medulla regions, whereas Hsp90 β was induced in the cortex. Immunoreactivity of pc-Src was elevated in PCT with obvious staining at the luminal membrane. This in vivo study is the first to demonstrate that aldosterone nongenomically elevates Hsp90( α and β ) protein expressions in rat kidney. Aldosterone had no effect on pc-Src protein levels but modulated localization. These results indicate that aldosterone regulates upstream mediators of EGFR transactivation in vivo.

EGFR activity is required for renal tubular cell dedifferentiation and proliferation in a murine model of folic acid-induced acute kidney injury

Proliferation of dedifferentiated intrinsic renal tubular cells has been recognized to be the major cellular event that contributes to renal repair after acute kidney injury (AKI). However, the underlying mechanism that initiates renal tubular dedifferentiation in vivo remains unexplored. Here we investigated whether epidermal growth factor receptor (EGFR) mediates this process in a murine model of folic acid (FA)-induced AKI using waved-2 mice that have reduced tyrosine kinase activity of EGFR and gefitinib, a specific EGFR inhibitor. Administration of FA for 48 h induced EGFR phosphorylation in the kidney of wild-type mice, but this was inhibited in waved-2 mice and wild-type mice given gefitinib. Compared with wild-type mice, waved-2 mice and wild-type mice treated with gefitinib had increased renal dysfunction, histologic damage, and tubular cell apoptosis after FA administration. PAX2, a dedifferentiation marker, and proliferating cell nuclear antigen, a proliferating marker, were highly expressed in renal tubular cells in wild-type mice; however, their expression was largely inhibited in the kidney of waved-2 mice. Inhibition of EGFR with gefitinib also blocked FA-induced expression of these two proteins in wild-type mice. Moreover, FA exposure resulted in phosphorylation of AKT, a downstream signaling molecule of the phosphatidylinositol 3-kinases pathway associated with renal epithelial proliferation in wild-type mice, and its phosphorylation was totally suppressed in waved-2 mice and wild-type mice given gefitinib. Taken together, these results suggest that EGFR activation is essential for initiation of renal tubular cell dedifferentiation and proliferation after AKI.

Src family kinases regulate renal epithelial dedifferentiation through activation of EGFR/PI3K signaling

Dedifferentiation, a process by which differentiated cells become mesenchymal-like proliferating cells, is the first step in renal epithelium repair and occurs in vivo after acute kidney injury and in vitro in primary culture. However, the underlying mechanism remains poorly understood. In this report, we studied the signaling events that mediate dedifferentiation of proximal renal tubular cells (RPTC) in primary culture. RPTC dedifferentiation characterized by increased expression of vimentin concurrent with decreased expression of cytokeratin-18 was observed at 24 h after the initial plating of freshly isolated proximal tubules and persisted for 72 h. At 96 h, RPTC started to redifferentiate as revealed by reciprocal expression of cytokeratin-18 and vimentin and completed at 120 h. Phosphorylation levels of Src, epidermal growth factor receptor (EGFR), AKT (a target of phosphoinositide-3-kinase (PI3K)), and ERK1/2 were increased in the early time course of culture (<72 h). Inhibition of Src family kinases (SFKs) with PP1 blocked EGFR, AKT, and ERK1/2 phosphorylation, as well as RPTC dedifferentiation. Inhibition of EGFR with AG1478 also blocked AKT and ERK1/2 phosphorylation and RPTC dedifferentiation. Although inactivation of the PI3K/AKT pathway with LY294002 inhibited RPTC dedifferentiation, blocking the ERK1/2 pathway with U0126 did not show such an effect. Moreover, inhibition of SFKs, EGFR, PI3K/AKT, but not ERK1/2 pathways abrogated RPTC outgrowth and SFK inhibition decreased RPTC proliferation and migration. These findings demonstrate a critical role of SFKs in mediating RPTC dedifferentiation through activation of the EGFR/PI3K signaling pathway.

The role of MAPK in drug-induced kidney injury

This paper focuses on the role that mitogen-activated protein kinases (MAPKs) play in drug-induced kidney injury. The MAPKs, of which there are four major classes (ERK, p38, JNK, and ERK5/BMK), are signalling cascades which have been found to be broadly conserved across a wide variety of organisms. MAPKs allow effective transmission of information from the cell surface to the cytosolic or nuclear compartments. Cross talk between the MAPKs themselves and with other signalling pathways allows the cell to modulate responses to a wide variety of external stimuli. The MAPKs have been shown to play key roles in both mediating and ameliorating cellular responses to stress including xenobiotic-induced toxicity. Therefore, this paper will discuss the specific role of the MAPKs in the kidney in response to injury by a variety of xenobiotics and the potential for therapeutic intervention at the level of MAPK signalling across different types of kidney disease.

Src tyrosine kinase inhibition prevents pulmonary ischemia-reperfusion-induced acute lung injury

PURPOSE

Pulmonary ischemia-reperfusion is a pathological process seen in several clinical conditions, including lung transplantation, cardiopulmonary bypass, resuscitation for circulatory arrest, atherosclerosis, and pulmonary embolism. A better understanding of its molecular mechanisms is very important.

METHODS

Rat left lung underwent in situ ischemia for 60 min, followed by 2 h of reperfusion. The gene expression profiles and Src protein tyrosine kinase (PTK) phosphorylation were studied over time, and PP2, an Src PTK inhibitor, was intravenously administered 10 min before lung ischemia to determine the role of Src PTK in lung injury.

RESULTS

Reperfusion following ischemia significantly changed the expression of 169 genes, with Mmp8, Mmp9, S100a9, and S100a8 being the most upregulated genes. Ischemia alone only affected expression of 9 genes in the lung. However, Src PTK phosphorylation (activation) was increased in the ischemic lung, mainly on the alveolar wall. Src PTK inhibitor pretreatment decreased phosphorylation of Src PTKs, total protein tyrosine phosphorylation, and STAT3 phosphorylation. It increased phosphorylation of the p85α subunit of PI3 kinase, a signal pathway that can inhibit coagulation and inflammation. PP2 reduced leukocyte infiltration in the lung, apoptotic cell death, fibrin deposition, and severity of acute lung injury after reperfusion. Src inhibition also significantly reduced CXCL1 (GRO/KI) and CCL2 (MCP-1) chemokine levels in the serum.

CONCLUSION

During pulmonary ischemia, Src PTK activation, rather than alteration in gene expression, may play a critical role in reperfusion-induced lung injury. Src PTK inhibition presents a new prophylactic treatment for pulmonary ischemia-reperfusion-induced acute lung injury.

Activation of Src mediates PDGF-induced Smad1 phosphorylation and contributes to the progression of glomerulosclerosis in glomerulonephritis

Platelet-derived growth factor (PDGF) plays critical roles in mesangial cell (MC) proliferation in mesangial proliferative glomerulonephritis. We showed previously that Smad1 contributes to PDGF-dependent proliferation of MCs, but the mechanism by which Smad1 is activated by PDGF is not precisely known. Here we examined the role of c-Src tyrosine kinase in the proliferative change of MCs. Experimental mesangial proliferative glomerulonephritis (Thy1 GN) was induced by a single intravenous injection of anti-rat Thy-1.1 monoclonal antibody. In Thy1 GN, MC proliferation and type IV collagen (Col4) expression peaked on day 6. Immunohistochemical staining for the expression of phospho-Src (pSrc), phospho-Smad1 (pSmad1), Col4, and smooth muscle α-actin (SMA) revealed that the activation of c-Src and Smad1 signals in glomeruli peaked on day 6, consistent with the peak of mesangial proliferation. When treated with PP2, a Src inhibitor, both mesangial proliferation and sclerosis were significantly reduced. PP2 administration also significantly reduced pSmad1, Col4, and SMA expression. PDGF induced Col4 synthesis in association with increased expression of pSrc and pSmad1 in cultured MCs. In addition, PP2 reduced Col4 synthesis along with decreased pSrc and pSmad1 protein expression in vitro. Moreover, the addition of siRNA against c-Src significantly reduced the phosphorylation of Smad1 and the overproduction of Col4. These results provide new evidence that the activation of Src/Smad1 signaling pathway plays a key role in the development of glomerulosclerosis in experimental glomerulonephritis.

Imatinib treatment duration is related to decreased estimated glomerular filtration rate in chronic myeloid leukemia patients

BACKGROUND

We analyzed the incidence of acute kidney injury and chronic renal failure in chronic myeloid leukemia (CML) patients using imatinib and investigated whether there is a relation between duration of imatinib therapy and decrease in estimated glomerular filtration rate (GFR).

PATIENTS AND METHODS

One hundred five CML patients on imatinib therapy were enrolled. Creatinine, urea, uric acid, and potassium measurements from imatinib treatment onset until the end of follow-up (median 4.5 years) were included in the analysis. GFR was estimated using the Chronic Kidney Disease Epidemiology Collaboration equation.

RESULTS

During follow-up, 7% of patients developed acute kidney injury; creatinine levels returned to baseline in only one of them. According to the regression equation, the mean baseline value of the estimated GFR was 88.9 ml/min/1.73 m(2). Estimated GFR decreased significantly with imatinib treatment duration; the mean decrease per year was 2.77 ml/min/1.73 m(2) (P < 0.001); 12% of patients developed chronic renal failure. Age, hypertension, and a history of chronic renal failure or interferon usage were not significantly related to the mean decrease in the estimated GFR over time.

CONCLUSION

The introduction of imatinib therapy in nonclinical trial CML patients is associated with potentially irreversible acute renal injury, and the long-term treatment may cause a clinically relevant decrease in the estimated GFR.

Renal failure associated with tyrosine kinase inhibitors--case report and review of the literature

Imatinib mesylate (IM), nilotinib and dasatinib are tyrosine kinase inhibitors (TKIs) that have revolutionized the treatment of chronic myeloid leukemia (CML). Data regarding the effect of TKIs on the kidney or their safety in patients with renal failure is lacking. We describe a patient with CML who developed renal failure during IM treatment which resolved upon discontinuation of the drug and was not exacerbated by the administration of nilotinib. The literature reporting on the association between TKIs and renal failure is reviewed and the postulated mechanisms including tubular dysfunction caused by the drug or tumor lysis syndrome are discussed.

Signaling components of redox active endosomes: the redoxosomes

Subcellular compartmentalization of reactive oxygen species (ROS) plays a critical role in transmitting cell signals in response to environmental stimuli. In this regard, signals at the plasma membrane have been shown to trigger NADPH oxidase-dependent ROS production within the endosomal compartment and this step can be required for redox-dependent signal transduction. Unique features of redox-active signaling endosomes can include NADPH oxidase complex components (Nox1, Noxo1, Noxa1, Nox2, p47phox, p67phox, and/or Rac1), ROS processing enzymes (SOD1 and/or peroxiredoxins), chloride channels capable of mediating superoxide transport and/or membrane gradients required for Nox activity, and novel redox-dependent sensors that control Nox activity. This review will discuss the cytokine and growth factor receptors that likely mediate signaling through redox-active endosomes, and the common mechanisms whereby they act. Additionally, the review will cover ligand-independent environmental injuries, such as hypoxia/reoxygenation injury, that also appear to facilitate cell signaling through NADPH oxidase at the level of the endosome. We suggest that redox-active endosomes encompass a subset of signaling endosomes that we have termed redoxosomes. Redoxosomes are uniquely equipped with redox-processing proteins capable of transmitting ROS signals from the endosome interior to redox-sensitive effectors on the endosomal surface. In this manner, redoxosomes can control redox-dependent effector functions through the spatial and temporal regulation of ROS as second messengers.

Src regulates cell cycle protein expression and renal epithelial cell proliferation via PI3K/Akt signaling-dependent and -independent mechanisms

Our recent studies showed that Src family kinases (SFKs) are important mediators of proliferation in renal proximal tubular cells (RPTC). In this study, we elucidate the signaling mechanisms that mediate SFK regulation of cell proliferation and cycle protein expression, and identify the SFK member responsible for these responses in a mouse RPTC line. Akt, a target of phosphoinositide-3-kinase (PI3K), and ERK1/2 were constitutively phosphorylated in RPTC cultured in the presence of serum. While treatment of cells with PP1, a specific SFK inhibitor, completely blocked phosphorylation of ERK1/2 and Akt, only inhibition of PI3K/Akt resulted in decreased RPTC proliferation. Incubation of cells with PP1 decreased cyclin D1 expression, decreased p27 and p57 phosphorylation, and increased p27 and p57 expression, two cyclin-dependent kinase inhibitors. Inhibition of the PI3K pathway decreased expression of cyclin D1 without altering expression of p27 and p57. In contrast, PP1 and PI3K inhibition had no effect on cyclin E and p21. Although RPTC expressed Src, Fyn, and Lyn, only siRNA-mediated knockdown of Src decreased RPTC proliferation, decreased cyclin D1 expression, and increased p27 and p57 expression. These data reveal that Src is a crucial mediator of RPTC proliferation and Src-mediated proliferation is associated with PI3K-dependent upregulation of cyclin D1 and PI3K-independent downregulation of p27 and p57.

Partial fanconi syndrome induced by imatinib therapy: a novel cause of urinary phosphate loss

Imatinib mesylate (Gleevec, Glivec; Novartis, Basel, Switzerland) is a specific tyrosine kinase inhibitor that has become the gold-standard treatment for patients with chronic myeloid leukemia. Several tyrosine kinases inhibited by imatinib are expressed in the kidney, and although the drug is usually well tolerated, several cases of acute renal failure were reported. We describe for the first time a case of a patient treated by imatinib for chronic myeloid leukemia who developed partial Fanconi syndrome with mild renal failure, which leads to a discussion of the pathophysiological characteristics of imatinib-induced renal toxicity. Patients on long-term imatinib treatment should be monitored for renal failure, as well as proximal tubule dysfunction, including hypophosphatemia.

Heparin-binding epidermal growth factor and Src family kinases in proliferation of renal epithelial cells

Our recent studies have shown that proliferation of renal proximal tubular cells (RPTC) in the absence of growth factors requires activation of the epidermal growth factor (EGF) receptor. We sought to identify the endogenous EGF receptor ligand and investigate the mechanism(s) by which RPTC proliferate in different models. RPTC expressed both pro- and cleaved forms of heparin-binding epidermal growth factor (HB-EGF) and several metalloproteinases (MMP-2, -3, -9, and ADAM10, ADAM17) that have been reported to cleave HB-EGF. Treatment of RPTC with CRM 197, an inhibitor of HB-EGF binding to the EGF receptor, or downregulation of HB-EGF with small interfering RNA inhibited RPTC proliferation following plating. Furthermore, GM6001 (pan-MMP inhibitor), tumor-necrosis factor protease inhibitor-1 (TAPI-1; MMP and ADAM17 inhibitor), and GW280264X (ADAM10 and -17 inhibitor), but not GI254023X (ADAM10 inhibitor), attenuated the proliferation after plating. Although EGF receptor activation is required for RPTC proliferation after oxidant injury, CRM197, GM6001, and TAPI-1 did not block this response. In contrast, inhibition of Src with PP1 blocked EGF receptor activation and RPTC proliferation after oxidant injury. In addition, PP1 treatment attenuated HB-EGF-enhanced RPTC proliferation. We suggest that RPTC proliferation after plating is mediated by HB-EGF produced through an autocrine/paracrine mechanism and RPTC proliferation following oxidant injury is mediated by Src without involvement of HB-EGF.

Alterations in protein tyrosine kinase pathways in rat liver following normothermic ischemia-reperfusion

The phosphoregulation of signal transduction pathways is a complex series of reactions that modulate the cellular response to ischemia-reperfusion (I-R). The aim of this study was to evaluate the effect of normothermic liver I-R on protein tyrosine phosphorylation, production of angiogenic growth factors, and activation of signal proteins in tyrosine kinase pathways. A segmental normothermic ischemia of the liver was induced in rats by occluding the blood vessels (including the bile duct) to the median and left lateral lobes for 120 minutes. Liver extracts from either ischemic or nonischemic lobes were prepared at 0, 1, 3, and 6 hours after reperfusion. Liver tyrosine phosphorylation of proteins was examined by Western blot analysis, whereas vascular endothelial growth factor (VEGF) mRNA was analyzed by Northern blot. In ischemic liver lobes, VEGF mRNA and total protein levels increased at 1 and 3 hours after reperfusion. Tyrosine phosphorylation of the VEGF receptor Flk-1 and the platelet-derived growth factor receptor (PDGF-R) was increased only at 1 hour after reperfusion, while c-Src tyrosine phosphorylation remained increased at 3 hours and remained up to 6 hours after reperfusion. In conclusion, 1-R led to alterations in protein tyrosine phosphorylation and increased expression of VEGF in rat liver.

Localized activation of Src-family protein kinases in the mouse egg

Recent studies in species that fertilize externally have demonstrated that fertilization triggers localized activation of Src-family protein kinases in the egg cortex. However, the requirement for Src-family kinases in activation of the mammalian egg is different from lower species and the objective of this study was to characterize changes in the distribution and activity of Src-family protein tyrosine kinases (PTKs) during zygotic development in the mouse. Immunofluorescence analysis of mouse oocytes and zygotes with an anti-phosphotyrosine antibody revealed that fertilization stimulated accumulation of P-Tyr-containing proteins in the egg cortex and that their abundance was elevated in the region overlying the MII spindle. In addition, the poles of the MII spindle exhibited elevated P-Tyr levels. As polar body extrusion progressed, P-Tyr-containing proteins were especially concentrated in the region of cortex adjacent to the maternal chromatin and the forming polar body. In contrast, P-Tyr labeling of the spindle poles eventually disappeared as meiosis II progressed to anaphase II. In approximately 24% of cases, the fertilizing sperm nucleus was associated with increased P-Tyr labeling in the overlying cortex and oolemma. To determine whether Src-family protein tyrosine kinases could be responsible for the observed changes in the distribution of P-Tyr containing proteins, an antibody to the activated form of Src-family PTKs was used to localize activated Src, Fyn or Yes. Activated Src-family kinases were found to be strongly associated with the meiotic spindle at all stages of meiosis II; however, no concentration of labeling was evident at the egg cortex. The absence of cortical Src-family PTK activity continued until the blastocyst stage when strong cortical activity became evident. At the pronuclear stage, activated Src-family PTKs became concentrated around the pronuclei in close association with the nuclear envelope. This pattern was unique to the earliest stages of development and disappeared by the eight cell stage. Functional studies using chemical inhibitors and a dominant-negative Fyn construct demonstrated that Src-family PTKs play an essential role in completion of meiosis II following fertilization and progression from the pronuclear stage into mitosis. These data suggest that while Src-family PTKs are not required for fertilization-induced calcium oscillations, they do play a critical role in development of the zygote. Furthermore, activation of these kinases in the mouse egg is limited to distinct regions and occurs at specific times after fertilization.

Phosphoregulation of Signal Transduction Pathways in Ischemia and Reperfusion

Ischemia/reperfusion (I/R) injury triggered by pathogenic processes, such as organ transplant dysfunction, stroke, myocardial infarction, and shock, stimulate both immune and inflammatory pathways. Inflammatory cell activation and cytotoxic cytokine expression are associated with reperfusion injury. The activation of these inflammatory mediators initiates several interconnected downstream cascades regulated by phosphorylation and dephosphorylation reactions. These complex phosphorylation-dependent signal transduction pathways ultimately initiate nuclear transcription of inflammatory as well as anti-inflammatory genes to repair and assist in the recovery of damaged cells. Radical oxygen species (ROS) production, under ischemic conditions, initiates a cascade of events regulated by phosphorylation/dephosphorylation reactions and inflammatory gene expression. This is a review of the current understanding of the phosphoregulatory mechanisms that mediate the complex processes of signal transduction secondary to I/R injury. The rationale for inhibiting or activating signaling pathways as a promising molecular target for ameliorating reperfusion injury in I/R-related diseases, such as stroke, myocardial infarction, and storage for transplantation, is discussed on the basis of a new understanding of the mechanisms modulating phosphoregulatory pathways. In addition, we present part of our ongoing research in this field with phosphoregulatory signal transduction and its potential application.

Fertilization triggers localized activation of Src-family protein kinases in the zebrafish egg

Fertilization triggers activation of Src-family kinases in eggs of various species including marine invertebrates and lower vertebrates. While immunofluorescence studies have localized Src-family kinases to the plasma membrane or cortical cytoplasm, no information is available regarding the extent to which these kinases are activated in different regions of the zygote. The objective of the present study was to detect the subcellular distribution of activated Src-family kinases in the fertilized zebrafish egg. An antibody specific for the active, non-phosphorylated form of Src-family PTKs was used to detect these activated kinases by immunofluorescence. The results demonstrate that Fyn, and possibly other Src family members are activated by dephosphorylation of the C-terminal tyrosine at fertilization. The activated Src-family kinases are asymmetrically distributed around the egg cortex with an area of higher kinase activity localized adjacent to the micropyle near the presumptive animal pole. Fertilization initially caused elevation of kinase activity in the cytoplasm underlying the micropyle, but this quickly spread to involve the entire zygote cortex. Later, during egg activation, formation of the blastodisc involved concentration of active Src-family kinase in the blastodisc cortex. As cytokinesis began, activated Src-family kinases were no longer limited to the cortex, but became more evenly distributed in the clear apical cytoplasm of the blastomeres. The results demonstrate that the cortex of the zebrafish egg is functionally differentiated and that fertilization triggers localized activation of Src-family kinases at the point of sperm entry, which subsequently progresses through the entire egg cortex.

Src protein tyrosine kinase family and acute inflammatory responses

Acute inflammatory responses are one of the major underlying mechanisms for tissue damage of multiple diseases, such as ischemia-reperfusion injury, sepsis, and acute lung injury. By use of cellular and molecular approaches and transgenic animals, Src protein tyrosine kinase (PTK) family members have been identified to be essential for the recruitment and activation of monocytes, macrophages, neutrophils, and other immune cells. Src PTKs also play a critical role in the regulation of vascular permeability and inflammatory responses in tissue cells. Importantly, animal studies have demonstrated that small chemical inhibitors for Src PTKs attenuate tissue injury and improve survival from a variety of pathological conditions related to acute inflammatory responses. Further investigation may lead to the clinical application of these inhibitors as drugs for ischemia-reperfusion injury (such as stroke and myocardial infarction), sepsis, acute lung injury, and multiple organ dysfunction syndrome.