Suramin promotes proliferation and scattering of renal epithelial cells

Effect of Suramin on Renal Proximal Tubular Cells Damage Induced by Cisplatin in Rats (Histological and Immunohistochemical Study)

Background:

Renal toxicity is the most common complication of cispaltin therapy that has broad-spectrum antitumor activity against a variety of human solid tumor. Suramin, a Food and Drug Administration-approved old drug is a polysulfonated compound of napthylurea originally designed to treat trypanosomiasis.

Aim:

The current work aimed to investigate the possible protective effect of different doses of suramin against cisplatin-induced renal proximal tubular cells (RPTCs) damage.

Material and Methods:

Fifty adult male rats were used and divided into five equal groups. Group I served as a control, group II received suramin alone (10 mg/kg). Groups III, IV and V were administered cisplatin once (5 mg/kg, intraperitoneally) alone or combined with low dosage suramin (5 mg/kg) or high dosage suramin (10 mg/kg) once intravenously respectively.

Results:

Compared with control rats, cisplatin administration caused proximal tubules damage, RPTCs vacuolation with pyknotic nuclei, loss of brush border and widespread caspase-3 immunostaining. Cisplatin-induced RPTCs toxicity was further confirmed morphometrically (a significantly decreased proximal tubular epithelium height and increased mean number of caspase-3-immunopositive cells). These changes were accompanied by biochemical alteration manifested as a significant increase of blood urea nitrogen and serum creatinine. Simultaneous administration of high-dose but not low-dose suramin to the cisplatin-treated rats improved the deleterious morphological and morphometrical effects on RPTCs and restored the aforementioned biochemical parameters to control values.

Conclusion:

In conclusion suramin in a dose dependant manner protects RPTCs from damage induced by cisplatin.

Single-cell RNA-seq identifies a reversible mesodermal activation in abnormally specified epithelia of p63 EEC syndrome

Mutations in transcription factor p63 are associated with developmental disorders that manifest defects in stratified epithelia including the epidermis. The underlying cellular and molecular mechanism is however not yet understood. We established an epidermal commitment model using human induced pluripotent stem cells (iPSCs) and characterized differentiation defects of iPSCs derived from ectrodactyly, ectodermal dysplasia, and cleft lip/palate (EEC) syndrome patients carrying p63 mutations. Transcriptome analyses revealed stepwise cell fate transitions during epidermal commitment: Specification from multipotent simple epithelium to basal stratified epithelia and ultimately to the mature epidermal fate. Differentiation defects of EEC iPSCs caused by p63 mutations occurred during the specification switch from the simple epithelium to the basal-stratified epithelial fate. Single-cell transcriptome and pseudotime analyses of cell states identified mesodermal activation that was associated with the deviated commitment route of EEC iPSCs. Integrated analyses of differentially regulated genes and p63-dependent dynamic genomic enhancers during epidermal commitment suggest that p63 directly controls epidermal gene activation at the specification switch and has an indirect effect on mesodermal gene repression. Importantly, inhibitors of mesodermal induction enhanced epidermal commitment of EEC iPSCs. Our findings demonstrate that p63 is required for specification of stratified epithelia, and that epidermal commitment defects caused by p63 mutations can be reversed by repressing mesodermal induction. This study provides insights into disease mechanisms underlying stratified epithelial defects caused by p63 mutations and suggests potential therapeutic strategies for the disease.

Renoprotective approaches and strategies in acute kidney injury

Acute kidney injury (AKI) is a major renal disease associated with high mortality rate and increasing prevalence. Decades of research have suggested numerous chemical and biological agents with beneficial effects in AKI. In addition, cell therapy and molecular targeting have been explored for reducing kidney tissue damage and promoting kidney repair or recovery from AKI. Mechanistically, these approaches may mitigate oxidative stress, inflammation, cell death, and mitochondrial and other organellar damage, or activate cytoprotective mechanisms such as autophagy and pro-survival factors. However, none of these findings has been successfully translated into clinical treatment of AKI. In this review, we analyze these findings and propose experimental strategies for the identification of renoprotective agents or methods with clinical potential. Moreover, we propose the consideration of combination therapy by targeting multiple targets in AKI.

Suramin protects from cisplatin-induced acute kidney injury

Cisplatin, a commonly used cancer chemotherapeutic, has a dose-limiting side effect of nephrotoxicity. Approximately 30% of patients administered cisplatin suffer from kidney injury, and there are limited treatment options for the treatment of cisplatin-induced kidney injury. Suramin, which is Federal Drug Administration-approved for the treatment of trypanosomiasis, improves kidney function after various forms of kidney injury in rodent models. We hypothesized that suramin would attenuate cisplatin-induced kidney injury. Suramin treatment before cisplatin administration reduced cisplatin-induced decreases in kidney function and injury. Furthermore, suramin attenuated cisplatin-induced expression of inflammatory cytokines and chemokines, endoplasmic reticulum stress, and apoptosis in the kidney cortex. Treatment of mice with suramin 24 h after cisplatin also improved kidney function, suggesting that the mechanism of protection is not by inhibition of tubular cisplatin uptake or its metabolism to nephrotoxic species. If suramin is to be used in the context of cancer, then it cannot prevent cisplatin-induced cytotoxicity of cancer cells. Suramin did not alter the dose-response curve of cisplatin in lung adenocarcinoma cells in vitro. In addition, suramin pretreatment of mice harboring lung adenocarcinomas did not alter the initial cytotoxic effects of cisplatin (DNA damage and apoptosis) on tumor cells. These results provide evidence that suramin has potential as a renoprotective agent for the treatment/prevention of cisplatin-induced acute kidney injury and justify future long-term preclinical studies using cotreatment of suramin and cisplatin in mouse models of cancer.

Suramin decreases injury and improves regeneration of ethanol-induced steatotic partial liver grafts

Steatotic grafts are excluded for use in partial liver transplantation (LT) because of the increased risk of primary nonfunction. This study investigated the effects of suramin, a polysulfonated naphthylurea, on the outcome of steatotic partial LT. Rat livers were harvested after acute ethanol treatment (6 g/kg, intragastric administration), reduced in size to ≈ 1/3, and transplanted. Serum alanine aminotransferase (ALT) and total bilirubin levels as well as hepatic necrosis and apoptosis were significantly higher after transplantation of fatty partial grafts (FPG) than lean partial grafts (LPG). Suramin (5 mg/kg, i.p.) decreased ALT by ≈ 60%, hyperbilirubinemia by 75%, necrosis by 83%, and apoptosis by 70% after FPG transplantation. Hepatic cellular 5-bromo-2'-deoxyuridine (BrdU) incorporation increased to 28% in LPG but was only 2% in FPG at 48 hours, and the mitotic index increased to 7% in LPG but was only 0.2% in FPG, indicating suppressed regeneration in FPG. Suramin increased BrdU incorporation and the mitotic index to 43% and 9%, respectively, in FPG. All FPG recipients died within 5 days. Suramin recovered survival of FPG to 62%. Tumor necrosis factor-α (TNF-α) mRNA was 2.2-fold higher in FPG than in LPG and was associated with activation of caspase-8 and caspase-3 in FPG. Suramin decreased TNF-α and caspase activation in FPG. Transforming growth factor-β (TGF-β), phospho-Smad2/3 and p21Cip1 were significantly higher in FPG than in LPG and suramin blocked TGF-β formation and its down-stream signaling pathway. Taken together, suramin improves the outcome of FPG transplantation, most likely by inhibition of TNF-α and TGF-β formation.

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.

Recovery from glycerol-induced acute kidney injury is accelerated by suramin

Acute kidney injury (AKI) is a common and potentially life-threatening complication after ischemia/reperfusion and exposure to nephrotoxic agents. In this study, we examined the efficacy and mechanism(s) of suramin in promoting recovery from glycerol-induced AKI, a model of rhabdomyolysis-induced AKI. After intramuscular glycerol injection (10 ml of 50% glycerol per kilogram) into male Sprague-Dawley rats, serum creatinine maximally increased at 24 to 72 h and then decreased at 120 h. Creatinine clearance (CrCl) decreased 75% at 24 to 72 h and increased at 120 h. Suramin (1 mg/kg i.v.) administered 24 h after glycerol accelerated recovery of renal function as demonstrated by increased CrCl, decreased renal kidney injury molecule-1, and improved histopathology 72 h after glycerol injection. Suramin treatment decreased interleukin-1β (IL-1β) mRNA, transforming growth factor-β(1) (TGF-β(1)), phospho-p65 of nuclear factor-κB (NF-κB), and cleaved caspase-3 at 48 h compared with glycerol alone. Suramin treatment also decreased glycerol-induced activation of intracellular adhesion molecule-1 (ICAM-1) and leukocyte infiltration at 72 h. Urinary/renal neutrophil gelatinase-associated lipocalin 2 (NGAL) levels, hemeoxygenase-1 expression, and renal cell proliferation were increased by suramin compared with glycerol alone at 72 h. Mechanistically, suramin decreases early glycerol-induced proinflammatory (IL-1β and NF-κB) and growth inhibitory (TGF-β(1)) mediators, resulting in the prevention of late downstream inflammatory effects (ICAM-1 and leukocyte infiltration) and increasing compensatory nephrogenic repair. These results support the hypothesis that delayed administration of suramin is effective in abrogating apoptosis, attenuating inflammation, and enhancing nephrogenic repair after glycerol-induced AKI.

Angiotensin II-induced cyclooxygenase 2 expression in rat aorta vascular smooth muscle cells does not require heterotrimeric G protein activation

Angiotensin II (AngII) initiates cellular effects via its G protein-coupled angiotensin 1 (AT(1)) receptor (AT(1)R). Previously, we showed that AngII-induced expression of the prostanoid-producing enzyme cyclooxygenase 2 (COX-2) was dependent upon nuclear trafficking of activated AT(1)R. In the present study, mastoparan (an activator of G proteins), suramin (an inhibitor of G proteins), 1-[6-[[17beta-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U73122; a specific inhibitor of phospholipase C), and sarcosine(1)-Ile(4)-Ile(8)-AngII (SII-AngII; a G protein-independent AT(1)R agonist) were used to determine the involvement of G proteins and AT(1A)R trafficking in AngII-stimulated COX-2 protein expression in human embryonic kidney-293 cells stably expressing AT(1A)/green fluorescent protein receptors and cultured vascular smooth muscle cells, respectively. Mastoparan alone stimulated release of intracellular calcium and increased COX-2 expression. Preincubation with mastoparan inhibited AngII-induced calcium signaling without altering AngII-induced AT(1A)R trafficking, p42/44 extracellular signal-regulated kinase (ERK) activation, or COX-2 expression. Suramin or U73122 had no significant effect on their own; they did not inhibit AngII-induced AT(1A)R trafficking, p42/44 ERK activation, or COX-2 expression; but they did inhibit AngII-induced calcium responses. SII-AngII stimulated AT(1A)R trafficking and increased COX-2 protein expression without activating intracellular calcium release. These data suggest that G protein activation results in increased COX-2 protein expression, but AngII-induced COX-2 expression seems to occur independently of G protein activation.

Suramin induces and enhances apoptosis in a model of hyperoxia-induced oligodendrocyte injury

Recent evidence suggests oxygen as a powerful trigger for cell death in the immature white matter, leading to periventricular leukomalacia (PVL) as a cause of adverse neurological outcome in survivors of preterm birth. This oligodendrocyte (OL) death is associated with oxidative stress, upregulation of apoptotic signaling factors (i.e., Fas, caspase-3) and decreased amounts of neurotrophins. In search of neuroprotective strategies we investigated whether the polysulfonated urea derivative suramin, recently identified as a potent inhibitor of Fas signaling, affords neuroprotection in an in vitro model of hyperoxia-induced injury to immature oligodendrocytes. Immature OLs (OLN-93) were subjected to 80% hyperoxia (48 h) in the presence or absence of suramin (0, 30, 60, 120 microM). Cell death was assessed by flow cytometry (Annexin V, caspase-3 activity assay) and immunohistochemistry for activated caspase-3. Immunoblotting for the death receptor Fas, cleaved caspase-8 and the phosphorylated isoform of the serine-threonin kinase Akt (pAkt) was performed. Suramin lead to OL apoptosis and potentiated hyperoxia-induced injury in a dose-dependent manner. Immunoblotting revealed increased Fas and caspase-8 expression by suramin treatment. This effect was significantly enhanced when suramin was combined with hyperoxia. Furthermore, pAkt levels decreased following suramin exposure, indicating interference with neurotrophin-dependent growth factor signaling. These data indicate that suramin causes apoptotic cell death and aggravates hyperoxia-induced cell death in immature OLs. Its mechanism of action includes an increase of previously described hyperoxia-induced expression of pro-apoptotic factors and deprivation of growth factor dependent signaling components.

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.

Inhibition of endosome-lysosome system acidification enhances porcine circovirus 2 infection of porcine epithelial cells

Recently, Misinzo et al. (G. Misinzo, P. Meerts, M. Bublot, J. Mast, H. M. Weingartl, and H. J. Nauwynck, J. Gen. Virol. 86:2057-2068, 2005) reported that inhibiting endosome-lysosome system acidification reduced porcine circovirus 2 (PCV2) infection of monocytic 3D4/31 cells. The present study examined the effect of inhibiting endosome-lysosome system acidification in epithelial cells, since epithelial cells support PCV2 infection in vivo and are used in culturing PCV2 in vitro. Ammonium chloride (NH(4)Cl), chloroquine diphosphate (CQ), and monensin were used to inhibit endosome-lysosome system acidification. NH(4)Cl, CQ, or monensin increased PCV2 (Stoon-1010) infection by 726% +/- 110%, 1,212% +/- 34%, and 1,100% +/- 179%, respectively, in porcine kidney (PK-15) cells; by 128% +/- 7%, 158% +/- 3%, and 142% +/- 11% in swine kidney cells; by 160% +/- 28%, 446% +/- 50%, and 162% +/- 56% in swine testicle (ST) cells; and by 313% +/- 25%, 611% +/- 86%, and 352% +/- 44% in primary kidney epithelial cells. Similarly, increased PCV2 infection was observed with six other PCV2 strains in PK-15 cells treated with endosome-lysosome system acidification inhibitors. The mechanism behind increased PCV2 infection was further investigated in PK-15 cells using CQ. PCV2 infection of PK-15 cells was increased only when CQ was added early during PCV2 infection. CQ did not affect PCV2 virus-like particle (VLP) attachment to PK-15 cells but increased the disassembly of internalized PCV2 VLPs. In untreated PK-15 cells, internalized PCV2 VLPs localized within the endosome-lysosome system. PCV2 infection of untreated 3D4/31 and PK-15 cells and CQ-treated PK-15 cells was blocked by a serine protease inhibitor [4-(2-aminoethyl) benzenesulfonyl fluoride hydrochloride] but not by aspartyl protease (pepstatin A), cysteine protease (E-64), and metalloprotease (phosphoramidon) inhibitors. These results suggest that serine protease-mediated PCV2 disassembly is enhanced in porcine epithelial cells but inhibited in monocytic cells after inhibition of endosome-lysosome system acidification.

Purinergic agonists stimulate lens Na-K-ATPase-mediated transport via a Src tyrosine kinase-dependent pathway

The Na-K-ATPase is vital for maintenance of lens transparency. Past studies using intact lens suggested the involvement of tyrosine kinases in short-term regulation of Na-K-ATPase. Furthermore, in vitro phosphorylation of a lens epithelial membrane preparation by Src family kinases (SFKs), a family of nonreceptor tyrosine kinases, resulted in modification of Na-K-ATPase activity. Here, the effect of purinergic agonists, ATP and UTP, on Na-K-ATPase function and SFK activation was examined in the rabbit lens. Na-K-ATPase function was examined using two different approaches, measurement of ouabain-sensitive potassium ((86)Rb) uptake by the intact lens, and Na-K-ATPase activity in lens epithelial homogenates. ATP and UTP caused a significant increase in ouabain-sensitive potassium ((86)Rb) uptake. Na-K-ATPase activity was increased in the epithelium of lenses pretreated with ATP. Lenses treated with ATP or UTP displayed activation of SFKs as evidenced by increased Western blot band density of active SFK (phosphorylated at the active loop Y416) and decreased band density of inactive SFKs (phosphorylated at the COOH terminal). A single PY416-Src immunoreactive band at approximately 60 kDa was observed, suggesting not all Src family members are activated. Immunoprecipitation studies showed that band density of active Src, and to a lesser extent active Fyn, was significantly increased, while active Yes did not change. Preincubation of the lenses with SFK inhibitor PP2 abolished the ATP-induced increase in ouabain-sensitive potassium ((86)Rb) uptake. The results suggest selective activation of Src and/or Fyn is part of a signaling mechanism initiated by purinergic agonists that increases Na-K-ATPase-mediated transport in the organ-cultured lens.

Differential effect of FGF and PDGF on cell proliferation and migration in osteoblastic cells

It has been known that growth factors such as fibroblast growth factor (FGF) and platelet-derived growth factor (PDGF) can promote proliferation and migration in a variety of cell types including osteoblastic cells. However, the mechanism underlying their action has not been clearly defined. The present study was undertaken to examine the effect of FGF and PDGF on cell proliferation and migration and to determine the role of extracellular signal-regulated kinase (ERK) and Akt in action of FGF and PDGF in osteoblastic cells. FGF enhanced proliferation in a dose- and time-dependent manner, whereas it did not affect cell migration. FGF induced a transient activation of ERK, but not Akt, which was inhibited by an inhibitor of MEK, the upstream kinase of ERK, but not by inhibitors of PI3K/Akt (LY294002), epidermal growth factor receptor (EGFR, AG1478), and Src (PP2). FGF-induced proliferation was inhibited by inhibitors of MEK/ERK and Src pathways. Exposure of cells to FGF stimulated transition of cell cycle from the G1 phase to S phase and increased phosphorylation of Rb. FGF-induced phosphorylation of Rb was attenuated by inhibitors of MEK/ERK and Src pathways. Cell migration studies indicated that PDGF stimulated migration, but it had no effect on cell proliferation. PDGF induced activation of ERK and Akt. The ERK activatin was inhibited by the Src inhibitor and the Akt activation was inhibited by inhibitors of EGFR and Src. PDGF-induced migration was inhibited by inhibitors of MEK/ERK, PI3K/Akt, EGFR and Src pathways. Taken together, these findings suggest that the MEK/ERK and Src pathways play an important role in the FGF-induced proliferation and signaling pathways involving MEK/ERK, EGFR, Src and PI3K/Akt mediate the PDGF-induced migration. These data are of importance in understanding the roles of these growth factors in osteoblastic cell proliferation and migration.

Mitogen-activated protein kinase signaling is involved in suramin-induced neurite outgrowth in a neuronal cell line

Suramin is a well-known antitrypanosomal drug and a novel experimental agent for the treatment of several cancers. Previous study showed that suramin is an activator of extracellular signal-regulated kinase (ERK1/2) signaling in several cell lines including Chinese hamster ovary cells, although the physiological relevance of this activation remains uncertain. Here, it was shown that suramin enhances neurite outgrowth concomitant with activation of ERK1/2 in Neuro-2a cells, a neuronal cell line. These neurite outgrowth and ERK1/2 activation were significantly inhibited by PD98059, an inhibitor of mitogen-activated protein kinase kinase, as well as by activation of endogenous adenosine A2A receptors. The suramin-induced phosphorylation of ERK1/2 was also inhibited by inhibitors of Src family kinases. This attenuation of ERK1/2 activity was accompanied by a significant decrease in suramin-induced neurite outgrowth. These results suggest that suramin activates the Src/ERK1/2 signaling pathway that induces neurite outgrowth, both of which are negatively regulated by cAMP produced in response to activation of endogenous adenosine A2A receptors.