Angiotensin II and basic fibroblast growth factor mitogenic pathways in human fetal mesangial cells

Stability and biological activity evaluations of PEGylated human basic fibroblast growth factor

BACKGROUND

Human basic fibroblast growth factor (hBFGF) is a heparin-binding growth factor and stimulates the proliferation of a wide variety of cells and tissues causing survival properties and its stability and biological activity improvements have received much attention.

MATERIALS AND METHODS

In the present work, hBFGF produced by engineered Escherichia coli and purified by cation exchange and heparin affinity chromatography, was PEGylated under appropriate condition employing 10 kD polyethylene glycol. The PEGylated form was separated by size exclusion chromatography. Structural, biological activity, and stability evaluations were performed using Fourier transform infrared (FITR) spectroscopy, 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assay and effect denaturing agent, respectively.

RESULTS

FITR spectroscopy revealed that both PEGylated and native forms had the same structures. MTT assay showed that PEGyalated form had a 30% reduced biological activity. Fluorescence spectrophotometry indicated that the PEGylated form denatured at higher concentrations of guanidine HCl (1.2 M) compared with native, which denatured at 0.8 M guanidine HCl.

CONCLUSIONS

PEGylation of hBFGF makes it more stable against denaturing agent but reduces its bioactivity up to 30%.

Comparison of ROCK and EGFR activation pathways in the progression of glomerular injuries in AngII-infused rats

AIM

The roles of rho-kinase (ROCK) and epidermal growth factor receptor (EGFR) were studied using an angiotensin II (AngII)-dependent hypertension rat model.

METHOD

Male Wistar rats were infused with AngII at a rate of 400 ng/kg body weight (BW)/min for 14 days. Effects of ROCK inhibitor, fasudil (20 mg/kg BW), and EGFR inhibitor, gefitinib (3 mg/kg BW), were studied.

RESULTS

AngII infusion increased blood pressure (BP; 220 ± 19 mmHg) as well as the number of proliferating cells in glomeruli judged by Ki67 and proliferating cell nuclear antigen immunostaining and urinary protein excretion (118 ± 19 mg/day). AngII also decreased p27 expression and increased cyclin D1 expression in glomeruli, as well as induced dissociation of the nephrin- and podocin-immunostaining patterns in podocytes. Treatment with fasudil or gefitinib completely inhibited glomerular cell proliferation without changing the BP. Although the decreased p27 expression was reversed by both treatments, cyclin D1 induction was abolished only by gefitinib. Fasudil significantly reduced proteinuria (57.2 ± 17.5 mg/day), but not gefitinib (133.3 ± 30.9 mg/day). The dissociation of podocin and nephrin was ameliorated by fasudil, but not by gefitinib.

CONCLUSION

ROCK and EGFR have distinct roles in proteinuria and glomerular cell proliferation in this model.

Isolation and structure determination of a sesquiterpene lactone (vernodalinol) from Vernonia amygdalina extracts

CONTEXT

Vernonia amygdalina Del. (VA; Asteraceae or Compositae) is a small tree growing throughout tropical Africa. It is widely used for food and medicinal purposes by local people. It was reported that it had several qualities, including anticancer activity.

OBJECTIVE

A sesquiterpene lactone, vernodalinol, was isolated from VA leaves. The first reported source of vernodalinol was in 2009 from a different plant, only (1)H NMR spectrum and no detailed structural analysis were carried out. No whole spectroscopic data were provided.

MATERIALS AND METHODS

VA dried leaves were extracted with 85% ethanol followed by further separation into four fractions by liquid-liquid extraction technique using various solvents: hexane, chloroform, and n-butanol. Vernodalinol was separated from the n-butanol fraction by column chromatography. The biological activity of vernodalinol was evaluated in estrogen receptor-positive (ER(+)) human breast carcinoma cells (MCF-7) in vitro.

RESULTS

Results indicated that vernodalinol (25 and 50 μg/mL) inhibited breast cancerous cell growth (DNA synthesis) by 34% (P < 0.025) and 40% (P < 0.025), respectively. It is reasonable to expect an LC(50) of 70-75 μg/mL for vernodalinol in MCF-7 cells.

DISCUSSION AND CONCLUSION

Vernodalinol structure was confirmed using a battery of spectroscopic methods, 1D and 2D NMR, high-resolution mass spectrometry (HR-MS), UV, IR, and X-ray. These results suggest that vernodalinol, although it has some biological activity, is likely to work in concert with other ingredients responsible for the anticancer activity exhibited of VA.

Basic fibroblast growth factor regulates persistent ERK oscillations in premalignant but not malignant JB6 cells

The regulation of extracellular signal-regulated kinase (ERK) oscillations in the context of wound healing and carcinogenesis have been investigated in premalignant and malignant JB6 mouse epidermal cells stimulated with basic fibroblast growth factor (bFGF) and 12-O-tetradecanoyl phorbol-13-acetate (TPA). In premalignant JB6 cells, bFGF stimulation (1) increases cellular phospho-ERK and phospho-c-Jun levels, (2) increases serum-dependent cell proliferation, (3) induces an apparent epithelial-to-mesenchymal transition, and (4) induces the persistent nuclear-cytosolic oscillation of an ERK1-green fluorescent protein (ERK1-GFP) chimera. In contrast, TPA induces persistent activation of ERK in the absence of oscillations and does not induce efficient migration. Treatment of malignant or transformed JB6 cells with bFGF is associated with a transient nuclear translocation of ERK1-GFP but not oscillations or efficient cell migration. Our data suggest that bFGF regulates ERK oscillations in premalignant but not malignant JB6 cells.

ANG II induces c-Jun NH2-terminal kinase activation and proliferation of human mesangial cells via redox-sensitive transactivation of the EGFR

We previously showed that ANG II induces mesangial cell (MC) proliferation via the JNK-activator protein-1 pathway. The present study attempted to determine the upstream mediators of JNK activation, with emphasis on reactive oxygen species (ROS) and the epidermal growth factor (EGF) receptor (EGFR). In cultured human MCs (HMCs), as early as 3 min, ANG II time dependently increased intracellular ROS production, which was sensitive to 10 microM diphenyleneiodonium sulfate and 500 microM apocynin, two structurally distinct NADPH oxidase inhibitors. In contrast, inhibitors of other oxidant-producing enzymes, including the mitochondrial complex I inhibitor rotenone, the xanthine oxidase inhibitor allopurinol, the cyclooxygenase inhibitor indomethacin, the lipoxygenase inhibitor nordihydroguiaretic acid, the cytochrome P-450 oxygenase inhibitor ketoconazole, and the nitric oxide synthase inhibitor N(G)-nitro-l-arginine methyl ester, were without effect. ANG II-induced ROS generation was inhibited by the angiotensin type 1 receptor antagonist losartan (10 muM) but not the angiotensin type 2 receptor antagonist PD-123319 (10 microM). ANG II induced translocation of p47(phox) and p67(phox) from the cytosol to the membrane. The antioxidants almost abolished the ANG II mitogenic response, as assessed by [(3)H]thymidine incorporation and cell number, associated with a remarkable blockade of the activation of EGFR (90% inhibition) and JNK (83% inhibition). The EGFR inhibitor AG-1478 was able to mimic the effect of antioxidants, in that it inhibited the mitogenic response and the JNK activation following ANG II treatment. Together, these data suggest that the ROS-EGFR-JNK pathway is involved in transducing the proliferative effect of ANG II in cultured HMCs.

Phospholipase C and Src modulate angiotensin II-induced cyclic AMP production in preglomerular microvascular smooth-muscle cells from spontaneously hypertensive rats

Our previous study indicates that the phospholipase C family (PLC) and Src kinase family (Src) modulate adrenoceptor-induced cAMP production in a negative and positive manner, respectively, in preglomerular vascular smooth-muscle cells (PGSMCs) obtained from spontaneously hypertensive rats (SHR). Because angiotensin II (Ang II) activates PLC and Src, and because PLC and Src inhibit and augment cAMP production, respectively, it is conceivable that the balance between these signal-transduction pathways determines whether Ang II increases or decreases cAMP production in SHR PGSMCs. In SHR PGSMCs, Ang II (500 nM) did not alter cAMP production in the absence or presence of PP1 (100 nM; inhibitor of Src). In the presence of U73122 (3 microM; inhibitor of PLC), Ang II stimulated cAMP production from 2.2 +/- 0.062 to 4.7 +/- 0.73 pmol/well. In another study in U73122-pretreated SHR PGSMCs, Ang II increased cAMP from 3.0 +/- 0.07 to 6.3 +/- 0.40 pmol/well, and this response was blocked by PP1. RT-PCR of 10 isoforms of Scr (Lck, Hck, Frk Fyn, Blk, Lyn, Fgr, Yes, Yrk, and c-Src) indicated that SHR PGSMCs preferentially express Frk, Fyn, Lyn, and c-Src. We conclude that in SHR PGSMCs, inhibition of PLC uncovers a stimulatory effect of Ang II on cAMP production that is mediated by Src family kinases, most likely Frk, Fyn, Lyn, and/or c-Src.

Different Effects of Growth Factors on Human Renal Early Distal Tubular Cells in vitro

BACKGROUND

In the kidney, recovery from tubular damage requires regenerative mechanisms leading to re-epithelialization of the injured tubules. Current evidence supports the para- or autocrine role of growth factors in repair and regeneration of ischemic or nephrotoxic experimental acute renal failure.

METHODS

We evaluated the effects of EGF, HGF, IGF-1, and bFGF on human renal thick ascending limb and distal convoluted cells (TALDC) in vitro. TALDC were isolated by immunomagnetic separation and cultured. Signal transduction of the growth factors was evaluated by Western blot of ERK1/2 MAP-K phosphorylation. Cell proliferation was measured by MTT assay and a fluorometric assay.

RESULTS

A significant, dose- and time-dependent phosphorylation of ERK1/2 could be detected exclusively after stimulation with EGF. No other growth factor induced a significant MAPK phosphorylation. In the same manner, proliferation assays showed a significant growth-promoting effect of EGF. Neither HGF, nor IGF-1 or bFGF showed a stimulative effect on TALDC proliferation.

CONCLUSION

The present study highlights the effects of growth factors on cultured TALDC and supports the hypothesis that in vivo EGF plays a para- or autocrine role during renal repair mechanisms.

Fusion of HIV-1 envelope-expressing cells to human glomerular endothelial cells through an CXCR4-mediated mechanism

A central question in the pathogenesis of HIV-associated thrombotic microangiopathic (HIV-TMA) lesions is whether the HIV-1 envelope glycoprotein (HIV-1 Env) can interact directly with human glomerular endothelial cells (HGECs) through specific HIV-1 co-receptors. The goal of this study was to determine whether cultured primary HGECs express significant levels of the major HIV-1 co-receptors CD4, CXCR4, and/or CCR5 to allow fusion interactions with HIV-1. The expression of CD4, CXCR-4 and CCR-5 was assessed in cultured HGECs by reverse transcriptase-polymerase chain reaction (RT-PCR) and flow cytometry using specific antibodies. The HIV-1 Env-mediated membrane fusion of target glomerular cells was evaluated by a fluorescent dye transfer-based cell-cell fusion microscopic method. HGECs express CXCR4 mRNA and protein as determined by RT-PCR and immunostaining with phycoerythrin-conjugated anti-CXCR4 Mab 12G5. CD4 and CCR5 were not detected in HGECs, either by RT-PCR or by surface immunostaining with specific antibodies. Incubation of HGECs with cells expressing a CD4-independent envelope strain (HIV-1IIIB-8x) and the CD4-dependent envelope strain (HIV-1IIIB) resulted in transfer of fluorescent dyes of approximately 20% after 8-16 h incubation at 37 degrees C. Incubation in the presence of inhibitors (C34, which blocks six-helix bundle formation, and AMD3100, which interacts with CXCR4) reduced dye transfer by 60%-80%, confirming that the dye transfer was specific with respect to gp120-gp41-mediated fusion. Cultured primary HGECs express CXCR4 but not CD4 or CCR5. The ability of HGECs to promote fusion by a CD4-independent HIV-1 envelope glycoprotein suggests that these cells may become a potential direct target of certain HIV-1 isolates.

c-Jun NH2-terminal kinase mediation of angiotensin II-induced proliferation of human mesangial cells

Angiotensin II (ANG II) has been shown to activate c-Jun NH2-terminal kinase (JNK) in cultured mesangial cells, but the functional implication of this phenomenon remains to be determined, largely due to the lack of an effective approach to block JNK. Therefore, the present study was carried out to examine whether JNK is involved in ANG II-induced cell proliferation in cultured human mesangial cells (HMCs) with the use of a newly developed JNK-selective blocker, SP-600125. Within minutes, treatment with 100 nM ANG II activated all three members of MAP kinase family, including extracellular signal-regulated protein kinase (Erk) 1/2, JNK, and p38 in cultured HMCs, as assessed by immunoblotting detection of phosphorylation of MAP kinases. ANG II-dependent activation of JNK was further confirmed by detection of increased phosphorylation and transcription activity of c-Jun after the ANG II treatment. SP-600125 ranging from 5 to 10 μM almost completely abolished the activation of JNK by ANG II without affecting the activities of Erk1/2 and p38. After treatment with 100 ng ANG II, there was a steady increase in [3H]thymidine incorporation that was blocked by SP-60025 in a dose- and time-dependent manner. Similarly, SP-600125 dose dependently reduced the ANG II-induced increase in cell number. The antiproliferative effect of SP-60025 was further determined by cell-cycle analysis with flow cytometry. Twenty-four hours after ANG II treatment, 50% of the quiescent HMCs (G0/G1) progressed into the S phase, and the cell cycle progression was almost completely prevented in the presence of SP-60025. Our data suggest that JNK mediates the proliferative effect of ANG II in cultured HMCs and thus represents a novel therapeutic target for treatment of chronic renal diseases.

Maturation-dependent changes of angiotensin receptor expression in fowl

An angiotensin (ANG) receptor homologous to the type 1 receptor (AT1) has been cloned in chickens (cAT1). We investigated whether cAT1 expression in various tissues shows maturation/age-dependent changes. cAT1 mRNA levels detected in renal glomeruli [in situ hybridization (ISH)] and kidney extract (RT-PCR) are significantly (P < 0.01) higher in 19-day embryos (EB) than in chicks (CH, 2-3 wk) and pullets/cockerels (PL/CK, 14-16 wk). The levels in adrenal glands (concentrated in subcapsular regions) are high in EB and further increased in CH and PL/CK. cAT1 mRNA is also detectable in smooth muscle (SM)/adventitia of EB and CH aorta and in the adventitia, but not SM, from PL/CK aortas. The endothelia from small arteries and arterioles, but not from aorta, express cAT1 mRNA (ISH). In all age groups, ANG II induces profound endothelium-dependent relaxation of abdominal aorta, partly (37-47%) inhibitable (P < 0.01) by Nomega-nitro-l-arginine methyl ester (l-NAME, 10(-4) M), suggesting the presence of ANG receptor in endothelium. l-NAME-resistant ANG II relaxation, examined in a limited number of EB or CH aortas, was reduced by 125 mM K+ or apamin plus charybdotoxin. The results suggest that 1) cAT1 is present in kidney, adrenal gland, and vascular endothelium (heterogeneity exists among arteries) of EB, CH, and PL/CK, and in aortic SM/adventitia of EB/CH but only in adventitia of PL/CK; 2) levels of cAT1 gene expression change during maturation in a tissue-specific manner; and 3) ANG II-induced relaxation may be partly attributable to nitric oxide and potassium channel activation.

Discovery of water-soluble anticancer agents (edotides) from a vegetable found in Benin City, Nigeria

Cancer claims the lives of more than six million people each year in the world. About 1,268,000 new cancer cases, and 553,400 deaths were reported in the United States in 2001. Current treatment approaches have yielded significant progress in the fight against cancer, but the incidence of developing certain types of cancer continues to rise. This is especially true in the African-American communities. African Americans are about 33% more likely to die of cancer than are whites and more than twice likely to die of cancer as are Asian-Islander, American-Indians, and Hispanics. This increase coupled with the harsh side effects of some of the cancer chemotherapies have led to the search for more natural biological products, especially those derived from plant products, currently known as herbal medicine. There is a need for a continued search for novel natural products that may be used as cancer chemopreventive and/or chemotherapeutic agents. The objective of this study was to evaluate the effect(s) of a novel water-soluble leaf extract of Vernonia amygdalina (VA) on human breast cancer cell DNA synthesis. MCF-7 cell line, considered a suitable model, was used in this study. Treatment of cells with physiologically relevant concentrations of water-soluble VA extract potently inhibited DNA synthesis in a concentration-dependent fashion both in the absence and presence of serum. Fractions of VA extract separated using preparative reverse-phase chromatography also inhibited DNA synthesis (P < 0.005). These results suggest that VA vegetable, if incorporated in the diet, may prevent or delay the on-set of breast cancer.

Apoptotic effect of sphingosine 1-phosphate and increased sphingosine 1-phosphate hydrolysis on mesangial cells cultured at low cell density

The lipid mediator sphingosine 1-phosphate (S1P) may alter the proliferation of mesangial cells during pathophysiological processes. Here, S1P stimulated proliferation of rat mesangial cells and phosphorylation of MAPKs at subconfluent cell density. Both effects were inhibited by pertussis toxin treatment. Mesangial cells expressed several S1P receptors of the endothelial differentiation gene family: EDG-1, -3, -5, and -8. Conversely, S1P induced apoptosis at low cell density (2 x 10(4) cells/cm(2)), which was demonstrated by flow cytometry and Hoechst staining. Apoptosis was observed also in quiescent or growing cells and was not reverted by lysophosphatidic acid or platelet-derived growth factor. S1P enhanced phosphorylation of SAPKs. Incubation with [(33)P]S1P, [(3)H]S1P, and [(3)H]sphingosine demonstrated increased S1P hydrolysis, resulting in enhanced intracellular sphingosine levels and decreased S1P levels. A rise in total ceramide levels was also observed; however, ceramide did not originate from [(3)H]sphingosine, and S1P-induced apoptosis was not inhibited by fumonisin B, precluding involvement of de novo ceramide synthesis in apoptosis. Therefore, we suggest that sphingosine accumulation and decreased S1P are primarily responsible for S1P-induced apoptosis. In conclusion, incubation of low-density mesangial cells with S1P results in apoptosis, presumably due to increased S1P hydrolysis.

Ethanol modulates the growth of human breast cancer cells in vitro

The role of ethanol or its metabolites on breast neoplasm has not been characterized. We hypothesized that ethanol may alter the growth rate of human breast tumor epithelial cells by modulating putative growth-promoting signaling pathways such as p44/42 mitogen-activated protein kinases (MAPKs). The MCF-7 cell line, considered a suitable model, was used in these studies to investigate the effects of ethanol on [(3)H]thymidine incorporation, cell number, and p44/42 MAPK activities in the presence or absence of a MAPK or extracellular signal-regulated kinase ERK-1, and (MEK1) inhibitor (PD098059). Treatment of MCF-7 cells with a physiologically relevant concentration of ethanol (0.3% or 65 mM) increased p44/42 activities by an average of 400% (P < 0.02), and subsequent cell growth by 200% (P < 0.05) in a MEK1 inhibitor (PD098059)-sensitive fashion, thus suggesting that the Ras/MEK/MAPK signaling pathways are crucial for ethanol-induced MCF-7 cell growth.

Adenovirus-mediated gene transfer to renal glomeruli in rodents

BACKGROUND

The expression of foreign genes into renal glomerular cells holds enormous potential to modulate the outcome of renal diseases. Recombinant adenoviruses (rAds) are promising gene transfer vectors because they have the ability to infect a wide range of nondividing cells. However, despite the fact that renal glomeruli are easily accessible via the renal circulation, adenovirus-mediated gene transfer into rodent glomeruli has been problematic. Here, we described our experience using rAd vectors to express foreign genes in rodent renal glomeruli in vivo and in cultured human renal glomerular cells.

METHODS

We developed two techniques--the "portal clamping" and "prolonged renal infusion"--to infect mouse and rat renal glomeruli in vivo, respectively. We used E-1-deleted rAd vectors carrying the lacZ gene encoding beta-galactosidase (Ad. CBlacZ) under the control of the cytomegalovirus enhancer and chicken beta-actin promoter. Cultured human renal glomerular podocytes, endothelial and mesangial cells were grown following standard techniques. Transgene expression was evaluated by doing beta-galactosidase staining and reverse transcription-polymerase chain reaction studies.

RESULTS

We found that both a prolonged exposure and a high concentration of circulating adenoviral vectors were required to achieve efficient gene transfer to renal glomerular cells in rodents. The virus-mediated transgene expression in renal glomeruli lasted for at least 42 days in mice and 21 days in rats without causing significant renal injury.

CONCLUSIONS

These data demonstrate the feasibility of using rAd vectors as a tool to express foreign genes in rodent renal glomerular cells and suggest that all types of human renal glomerular cells are equally susceptible to rAd infection.

Up-regulation of a fibroblast growth factor binding protein in children with renal diseases

BACKGROUND

Basic fibroblast growth factor (bFGF) is an angiogenic growth factor that is involved in renal growth and the pathogenesis of renal diseases. We have detected high levels of bFGF accumulated in the kidney of HIV-transgenic mice and in children with HIV-associated renal diseases and the hemolytic uremic syndrome (HUS). However, the mechanism modulating the activity of bFGF under these circumstances is poorly understood. We carried out experiments to determine whether a secreted binding protein (FGF-BP) that modulates the activity of bFGF during the process of tumor growth was expressed in pediatric kidneys and to define whether the expression of FGF-BP was altered in pediatric renal diseases associated with high levels of bFGF.

METHODS

Immunohistochemistry and in situ hybridization studies were done in 41 renal sections from children with HIV nephropathies, HUS, other pediatric renal diseases, controls, and fetal kidneys. Western blots and reverse transcriptase-polymerase chain reaction studies were done in selected urine samples and cultured renal cells. Recombinant FGF-BP was produced to study the mitogenic activity of FGF-BP in cultured human renal proximal tubular epithelial cells (RPTEcs).

RESULTS

The expression of FGF-BP was up-regulated predominately in renal tubular epithelial cells in children with renal tubular injury, HIV-associated nephropathy (HIVAN), and HUS, and FGF-BP was secreted in the urine of these patients. FGF-BP was also abundantly expressed in developing fetal renal tubules. Recombinant FGF-BP enhanced the mitogenic effects of bFGF in cultured human RPTEcs.

CONCLUSIONS

The localization of FGF-BP in renal tubular epithelial cells could provide a mechanism by which the activity of bFGF is modulated in developing and regenerating renal tubules of children.