Zinc supplementation reduces RANKL/OPG ratio and prevents bone architecture alterations in ovariectomized and type 1 diabetic rats.

Type 1 diabetes mellitus (T1DM) and estrogen deficiency are associated with several alterations in bone turnover. Zinc (Zn) is required for growth, development, and overall health. Zinc has been used in complementary therapy against bone loss in several diseases. We hypothesized that Zn supplementation represents a potential therapy against severe bone loss induced by the combined effect of estrogen deficiency and T1DM. We evaluated the protective effect of Zn against bone alterations in a chronic model of these disorders. Female Wistar rats were ramdomized into 3 groups (5 rats each): control, OVX/T1DM (ovariectomized rats with streptozotocin-induced T1DM), and OVX/T1DM+Zn (OVX/T1DM plus daily Zn supplementation). Serum biochemical, bone histomorphometric, and molecular analyses were performed. Histomorphometric parameters were similar between the control and OVX/T1DM+Zn groups, suggesting that Zn prevents bone architecture alterations. In contrast, the OVX/T1DM group showed significantly lower trabecular width and bone area as well as greater trabecular separation than the control. The OVX/T1DM and OVX/T1DM+Zn groups had significantly higher serum alkaline phosphatase activity than the control. The supplemented group had higher levels of serum-ionized calcium and phosphorus than the nonsupplemented group. The RANKL/OPG ratio was similar between the control and OVX/T1DM+Zn groups, whereas it was higher in the OVX/T1DM group. In conclusion, Zn supplementation prevents bone alteration in chronic OVX/T1DM rats, as demonstrated by the reduced RANKL/OPG ratio and preservation of bone architecture. The findings may represent a novel therapeutic approach to preventing OVX/T1DM-induced bone alterations.

Association of the PPP3CA c.249G>A variant with clinical outcomes of tacrolimus-based therapy in kidney transplant recipients.

BACKGROUND: The effects of genetic variants related to the pharmacodynamic mechanisms of immunosuppressive drugs on their therapeutic efficacy and safety have been poorly explored. This study was performed to investigate the influence of the PPP3CA c.249G>A variant on the clinical outcomes of kidney transplant recipients. PATIENTS AND METHODS: A total of 148 Brazilian patients received tacrolimus (TAC)-based immunosuppressive therapy for 90 days post-kidney transplantation. The PPP3CA rs3730251 (c.249G>A) polymorphism was determined by real-time polymerase chain reaction. Single-nucleotide polymorphism (SNP) data for CYP3A5 rs776746 (CYP3A5*3C; g.6986A>G) were used to eliminate the confounding effects of this variant. RESULTS: The PPP3CA c.249G>A SNP did not influence early TAC exposure, renal function, or other laboratory parameters, including levels of urea, creatinine, glucose, and lipids, and blood counts. This variant also did not account for the cumulative incidence of biopsy-confirmed acute rejection or delayed graft function. Regarding adverse events, PPP3CA c.249A allele carriers initially had a 3.05-fold increased probability of treatment-induced blood and lymphatic system disorders compared with c.249GG genotype individuals (95% confidence interval: 1.10-8.48, p=0.032). However, this result was not maintained after adjusting for body weight and CYP3A5*3C SNP status (p=0.086). CONCLUSION: The PPP3CA c.249G>A variant does not influence the clinical outcomes of Brazilian patients in the early phase of TAC-based immunosuppressive regimen.

Influence of ABCC2, CYP2C8, and CYP2J2 Polymorphisms on Tacrolimus and Mycophenolate Sodium-Based Treatment in Brazilian Kidney Transplant Recipients.

STUDY OBJECTIVE: To investigate the influence of single nucleotide polymorphisms (SNPs) in genes encoding metabolizing enzymes (CYP2C8, CYP2J2, and UGT2B7) and transporters (ABCC2 and ABCG2) on dose and dose-adjusted trough blood concentrations (C:D ratio), clinical outcomes, and occurrence of adverse events of tacrolimus and mycophenolate sodium in Brazilian kidney transplant recipients. DESIGN: Pharmacogenetic analysis of patients enrolled in a previously published study. PATIENTS: One hundred forty-eight adult kidney transplant recipients treated with tacrolimus, enteric-coated mycophenolate sodium, and prednisone for 90 days posttransplantation. MEASUREMENTS AND MAIN RESULTS: ABCC2 c.-24C>T and c.3972C>T, ABCG2 c.421C>A, CYP2C8*3, CYP2J2 c.-76G>T, and UGT2B7 c.372A>G SNPs were determined by real-time polymerase chain reaction. The CYP3A5*3C SNP data were used to eliminate the confounding effect of this variant on the results. ABCC2 c.3972T allele carriers showed higher tacrolimus C:D values than did carriers of the c.3972CC genotype. The CYP2C8*3 variant was also associated with slightly higher tacrolimus C:D values and higher estimated glomerular filtration rate but only in CYP3A5-nonexpressing patients (CYP3A5*3C/*3C carriers). None of the SNPs were associated with mycophenolate sodium dose or episodes of biopsy-confirmed acute rejection or delayed graft function. The CYP2J2 c.-76T allele was associated with increased risk for treatment-induced nausea and/or vomiting (OR: 5.30, 95% confidence interval 1.49-18.79, p<0.05). CONCLUSION: The ABCC2 c.3972C >T polymorphism affected tacrolimus C:D in Brazilian kidney transplant recipients. Further, CYP2C8*3 and CYP2J2 c.-76G>T SNPs influenced the renal function of these patients and the occurrence of adverse events during treatment with tacrolimus and mycophenolate sodium.

FRTL-5 Rat Thyroid Cells Release Thyroglobulin Sequestered in Exosomes: A Possible Novel Mechanism for Thyroglobulin Processing in the Thyroid.

Exosomes are 30-100 nm, membrane-bound vesicles containing specific cellular proteins, mRNAs, and microRNAs that take part in intercellular communication between cells. A possible role for exosomes in thyroid function has not been fully explored. In the present study, FRTL-5 rat thyroid cells were grown to confluence and received medium containing either thyroid stimulating hormone (TSH), exogenous bovine thyroglobulin (bTg), or neither additive for 24 or 48 hours followed by collection of spent medium and ultracentrifugation to isolate small vesicles. Transmission electron microscopy and Western blotting for CD9 indicated the presence of exosomes. Western blotting of exosome extract using a monoclonal anti-Tg antibody revealed a Tg-positive band at ~330 kDa (the expected size of monomeric Tg) with a higher density in TSH-treated cells compared to that in untreated cells. These results are the first to show that normal thyroid cells in culture produce exosomes containing undegraded Tg.

Influence of the CYP3A4/5 genetic score and ABCB1 polymorphisms on tacrolimus exposure and renal function in Brazilian kidney transplant patients.

BACKGROUND: Polymorphisms in genes encoding transport proteins and metabolizing enzymes involved in tacrolimus (TAC) disposition may be important sources of individual variability during treatment. OBJECTIVE: The aim of this study was to investigate the effect of combined CYP3A4 and CYP3A5 variants, using a CYP3A4/5 genetic score, and ABCB1 polymorphisms on therapeutic TAC monitoring and their relationship with clinical outcomes. MATERIAL AND METHODS: Brazilian kidney transplant recipients (n=151), who received TAC over 3 months after transplantation, were genotyped for CYP3A4 rs2242480 (g.20230G>A), CYP3A5 rs15524 (g.31611C>T) and rs776746 (g.6986A>G), ABCB1 rs1128503 (c.1236C>T), rs1045642 (c.3435C>T), and rs2032582 (c.2677G>T/A) polymorphisms. RESULTS: Frequencies of CYP3A4 g.20230A, CYP3A5 g.31611C, and g.6986A were 0.37, 0.26, and 0.28, respectively. These alleles were associated with TAC rapid metabolization and were used for CYP3A4/5 genetic score construction. A higher CYP3A4/5 genetic score was associated with higher TAC dose and lower concentrations for dose administered (Co/D, P<0.05). Ninety days after transplantation, the presence of two or more rapid metabolization alleles contributed toward 27.7% of Co/D variability and was associated with a lower estimated glomerular filtration rate values (P<0.05). For ABCB1, the frequencies of c.1236T, c.3435T, and c.2677T/A alleles were 0.42, 0.42, and 0.33/0.04. At 30 days after transplantation, patients carrying ABCB1 c.1236TT+c.3435TT+(c.2677TT+TA) genotypes had higher TAC Co/D than those with common or heterozygous genotypes (P<0.05). CONCLUSION: The results show the impact of the CYP3A4/5 genetic score on TAC exposure and renal function in Brazilian patients. Furthermore, ABCB1 polymorphisms, in a combined analysis, influenced TAC Co/D at 30 days after transplantation.

Mitochondrial bioenergetics and oxidative status disruption in brainstem of weaned rats: Immediate response to maternal protein restriction.

Mitochondrial bioenergetics dysfunction has been postulated as an important mechanism associated to a number of cardiovascular diseases in adulthood. One of the hypotheses is that this is caused by the metabolic challenge generated by the mismatch between prenatal predicted and postnatal reality. Perinatal low-protein diet produces several effects that are manifested in the adult animal, including altered sympathetic tone, increased arterial blood pressure and oxidative stress in the brainstem. The majority of the studies related to nutritional programming postulates that the increased risk levels for non-communicable diseases are associated with the incompatibility between prenatal and postnatal environment. However, little is known about the immediate effects of maternal protein restriction on the offspring's brainstem. The present study aimed to test the hypothesis that a maternal low-protein diet causes tissue damage immediately after exposure to the nutritional insult that can be assessed in the brainstem of weaned offspring. In this regard, a series of assays was conducted to measure the mitochondrial bioenergetics and oxidative stress biomarkers in the brainstem, which is the brain structure responsible for the autonomic cardiovascular control. Pregnant Wistar rats were fed ad libitum with normoprotein (NP; 17% casein) or low-protein (LP; 8% casein) diet throughout pregnancy and lactation periods. At weaning, the male offsprings were euthanized and the brainstem was quickly removed to assess the mitochondria function, reactive oxygen species (ROS) production, mitochondrial membrane electric potential (ΔΨm), oxidative biomarkers, antioxidant defense and redox status. Our data demonstrated that perinatal LP diet induces an immediate mitochondrial dysfunction. Furthermore, the protein restriction induced a marked increase in ROS production, with a decrease in antioxidant defense and redox status. Altogether, our findings suggest that LP-fed animals may be at a higher risk for oxidative metabolism impairment throughout life than NP-fed rats, due to the immediate disruption of the mitochondrial bioenergetics and oxidative status caused by the LP diet.

MicroRNAs in Renal Cell Carcinoma.

New therapies based on the targeting of signal pathways (such as VHL/HIF-1) common to most renal cell carcinomas (RCC), have greatly improved the outlook for sufferers of this disease. Given the growing reputation of many microRNAs (miRNAs) as both tumor suppressors and oncogenes, the measurement and manipulation of these small nucleotides in RCC patients may provide yet another valuable advance in renal cancer diagnosis and treatment. The present review summarizes the current literature on the role of microRNAs in RCC development and progression emphasizing the interaction of specific miRNAs with both oncogenic and tumor suppressor pathways of particular importance in renal cancer.

Effects of Traumatic Amputation on ß-Trace Protein and ß2-Microglobulin Concentrations in Male Soldiers.

BACKGROUND: Serum creatinine (SCr) levels are decreased following traumatic amputation, leading to the overestimation of glomerular filtration rate (GFR). ß-Trace protein (BTP) and ß2-microglobulin (B2M) strongly correlate with measured GFR and have not been studied following amputation. We hypothesized that BTP and B2M would be unaffected by traumatic amputation. METHODS: We used the Department of Defense Serum Repository to compare pre- and post-traumatic amputation serum BTP and B2M levels in 33 male soldiers, via the N Latex BTP and B2M nephelometric assays (Siemens Diagnostics, Tarrytown, N.Y., USA). Osterkamp estimation using DEXA scan measurements was used to establish percent estimated body weight loss (%EBWL). Results were analyzed for small (3-5.9% EBWL), medium (6-13.5%), and large (>13.5%) amputation subgroups; and for a control group matched 1:1 to the 12 large amputation subjects. Paired Student's t test was used for comparisons. RESULTS: Mean serum BTP levels were unchanged in controls, all amputees, and the small and medium amputation subgroups. BTP appeared to decrease following large %EBWL amputation (p = 0.05). Mean serum B2M levels were unchanged in controls, all amputees, and the small and medium amputation subgroups. B2M appeared to increase following large %EBWL amputation (p = 0.05). CONCLUSIONS: BTP and B2M levels are less affected than SCr by amputation, and should be considered for future study of GFR estimation. BTP and B2M changes following large %EBWL amputation require validation and may offer insight into non-GFR BTP and B2M determinants as well as increased cardiovascular disease and mortality following amputation.

Procalcitonin induced cytotoxicity and apoptosis in mesangial cells: implications for septic renal injury.

OBJECTIVE AND DESIGN: Immuno-neutralization of procalcitonin (ProCT) has been shown to ameliorate experimental sepsis as well as the renal complications of this disease. Accordingly, we investigated the direct effect of ProCT on mesangial cells (MCs). MATERIAL: Primary culture of murine MCs. TREATMENT: ProCT (0.5, 1.0, 2.5, 5.0 ng/ml) for 2, 4, 6 h. METHODS: MCs were exposed in vitro to ProCT. Expression levels of IL-6, iNOS and TNF-α were determined by real time RT-PCR, Inflammatory pathways, and a panel of cytokines and chemokines involved in the process were investigated by PCR array; apoptosis/viability were evaluated in a multiplex assay and actin cytoskeleton alterations were examined by immunofluorescence (IF). RESULTS: ProCT caused an early elevation in both IL-6 and iNOS mRNA (2-4 h), and a later rise (6 h) in TNF-α mRNA. ProCT upregulated genes of proinflammatory pathways 5- to 24-fold compared to control. IF images revealed disruption of the actin cytoskeleton and retraction of cell bodies with loss of typical stellate or spindle shape phenotype. ProCT decreased MCs viability by 36 % compared to control cells and induced significant apoptosis. CONCLUSIONS: ProCT has direct cytotoxic properties and may play a role in septic acute kidney injury that is independent of endotoxemia or hemodynamic alterations.

Transforming growth factor-beta1 regulation of C-type natriuretic peptide expression in human vascular smooth muscle cells: dependence on TSC22D1.

C-type natriuretic peptide (CNP) possesses nitric oxide-like signaling mechanisms and actions in the vasculature, including the inhibition of fibrosis and vascular remodeling through counterregulation of transforming growth factor-ß (TGF-ß) signaling. The leucine zipper protein transforming growth factor stimulated clone 22 domain 1 (TSC22D1), cloned via its presumed binding to a GC-rich element in the CNP promoter, was the first protein to be described as a CNP transcription factor, but the lack of supporting evidence since its discovery and its lack of a classical DNA-binding site have left in question its role in the regulation of CNP by TGF-ß and other factors. To define a specific role for TSC22D1 in CNP transcription, we have examined the effects of the profibrotic growth factors TGF-ß1 and PDGF-BB on CNP mRNA expression in cultured human vascular smooth muscle cells (SMC) in which TSC22D1 expression was suppressed with small interfering RNA. Results showed that TGF-ß and PDGF-BB significantly increased CNP expression in all three SMC types. Twenty-four-hour TGF-ß-induced elevations in CNP were strongly correlated with changes in TSC22D1 mRNA levels, and both genes exhibited their greatest response to TGF-ß1 in coronary artery SMC. Furthermore, siRNA suppression of TSC22D1 expression in coronary artery and aortic SMC by ∼90% resulted in 45-65% reductions of both PDGF- and TGF-ß-stimulated CNP expression, respectively. These results support a postulated role of TSC22D1 as an enhancer of CNP transcription and suggest that TGF-ß-induced upregulation of CNP expression in SMC may be mediated in part by increased transcription of TSC22D1.

Increased class A scavenger receptor and glomerular lipid precede mesangial matrix expansion in the bGH mouse model.

OBJECTIVE: Elevated neutral lipid content and mRNA expression of class A scavenger receptor (SRA) have been found in the renal cortex of the bovine growth hormone (bGH) mouse model of progressive glomerulosclerosis (GS). We hypothesize that the increased expression of SRA precedes glomerular scarring in this model. DESIGN: Real time RT-PCR and immunofluorescence were employed to measure SRA and collagen types I and IV in the bGH transgenic and control mice at 5 and 12 weeks (wk) of age to determine the chronology of change in SRA expression in relation to glomerular scarring. Alternative mechanisms for increasing glomerular lipid were assessed by measuring mRNA expression levels of low-density lipoprotein receptor (LDL-r), 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), and ATP-binding cassette transporter A1 (ABCA1). In addition, the involvement of macrophages in early GS was assessed by CD68 mRNA expression in kidney cortex. RESULTS: Both mRNA and protein levels of SRA were significantly increased in 5-wk bGH compared with control mice, whereas the expression of collagen I and IV was unaltered. Unchanged levels of LDL-r and HMGR mRNA indicate that neither regulated cholesterol uptake via LDL-r nor the cholesterol synthetic pathway played a role in the early lipid increase. The finding of increased ABCA1 expression was an indicator of excess intracellular lipid in the renal cortex of bGH mice at 5 wk. CD68 expression in bGH did not differ significantly from that of controls at 5 wk suggesting that cortical macrophage infiltration was not increased in bGH mice at this time point. CONCLUSION: An early increase in SRA mRNA and protein expression in the bGH kidney precedes glomerular scarring and is independent of macrophage influx.

Expression of a thyroglobulin (Tg) variant in mouse kidney glomerulus.

Thyroglobulin (Tg) is an essential substrate for thyroid hormone biosynthesis whose production is primarily limited to the thyroid follicular cell. We have previously identified an approximately 1.2 kb fragment of Tg mRNA in cultured mouse mesangial cells, and in the present study provide evidence showing that this transcript is transcribed and translated into a unique protein (kTg) in the kidney, but not the thyroid gland. Cloning of kTg from a mouse kidney cDNA library showed that transcription starts in the middle of intron 41 of the Tg gene and continues in-frame with the remaining coding sequence of thyroid-derived Tg beginning with exon 42. Translation of this mRNA is predicted to yield a protein of 367 amino acids (40 kDa) containing a unique 13 amino acid sequence serving as a signal peptide followed by a 354 amino acid segment identical to the carboxy-terminal end of thyroid Tg. Western blot analysis with an antibody directed against the C-terminus of thyroid Tg detected a 40 kDa protein expressed in the kidney. Immunohistochemistry with this antibody showed that immunoreactive Tg was localized in podocytes and the mesangial area of the renal glomerulus. A part of a homologous transcript was also detected in human kidney, and the kTg protein was recognized by sera from Hashimoto's thyroiditis but not from controls. Together these results suggest that a unique low molecular weight variant of Tg is expressed in the kidney, where it could serve both physiological and pathological roles, including that of an autoantigen.

Detection of the TLR4 1196C>T polymorphism by mismatched-polymerase chain reaction using plasmid DNA as internal control in restriction fragment length polymorphism assays.

BACKGROUND: Restriction fragment length polymorphism (RFLP) is a common molecular assay used for genotyping, and it requires validated quality control procedures to prevent mistyping caused by impaired endonuclease activity. We have evaluated the usefulness of a plasmid-based internal control in RFLP assays. RESULTS: Blood samples were collected from 102 individuals with acute myocardial infarction (AMI) and 108 non-AMI individuals (controls) for DNA extraction and laboratory analyses. The 1196C > T polymorphism in the toll-like receptor 4 (TLR4) gene was amplified by mismatched-polymerase chain reaction (PCR). Amplicons and pBluescript II SK- plasmid were simultaneously digested with endonuclease HincII. Fragments were separated on 2% agarose gels. Plasmid was completely digested using up to 55.2 nmL/L DNA solutions and 1 microL PCR product. Nevertheless, plasmid DNA with 41.4 nM or higher concentrations was incompletely digested in the presence of 7 microL PCR product. In standardized conditions, TLR4 1196C>T variant was accurately genotyped. TLR4 1196T allele frequency was similar between AMI (3.1%) and controls (2.0%, p = 0.948). TLR4 SNP was not associated with AMI in this sample population. In conclusion, the plasmid-based control is a useful approach to prevent mistyping in RFLP assays, and it is validate for genetic association studies such as TLR4 1196C>T.

Lysophosphatidylcholine increases C-type natriuretic peptide expression in human vascular smooth muscle cells via membrane distortion.

C-type natriuretic peptide (CNP) inhibits the migration of vascular smooth muscle cells (VSMC) and related cell types induced by oxidized LDL and its major atherogenic component, lysophosphatidylcholine (LPC). CNP expression is increased in smooth muscle in atherosclerotic and restenotic lesions, but mechanisms underlying this increase have not been elucidated. We therefore investigated the role of LPC in CNP expression in human aortic VSMC. Both LDL and HDL elevated CNP transcript levels approximately 3-fold in VSMC, but not in endothelial cells. Increasing LPC in both VSMC and endothelial cells induced significant elevations in CNP transcript levels that were correlated with the degree of LPC-induced membrane distortion, and that were abolished by stabilizing cell membranes with cholesterol:methyl-beta cyclodextrin complexes or by chelating intracellular Ca2+ with BAPTA/AM. CNP up-regulation in HAoSMC by both LPC and lysophosphatidic acid was dependent on intact tyrosine kinase and protein kinase C (PKC)-signaling, whereas it was independent of these pathways in endothelial cells. LPC-induced up-regulation of CNP mRNA in human VSMC results from membrane damage and Ca2+ influx and subsequent tyrosine kinase and PKC signaling, suggesting a means by which vascular damage by ox-LDL and LPC could initiate CNP-mediated vasoprotection.

Specific and sensitive detection of H. pylori in biological specimens by real-time RT-PCR and in situ hybridization.

PCR detection of H. pylori in biological specimens is rendered difficult by the extensive polymorphism of H. pylori genes and the suppressed expression of some genes in many strains. The goal of the present study was to (1) define a domain of the 16S rRNA sequence that is both highly conserved among H. pylori strains and also specific to the species, and (2) to develop and validate specific and sensitive molecular methods for the detection of H. pylori. We used a combination of in silico and molecular approaches to achieve sensitive and specific detection of H. pylori in biologic media. We sequenced two isolates from patients living in different continents and demonstrated that a 546-bp domain of the H. pylori 16S rRNA sequence was conserved in those strains and in published sequences. Within this conserved sequence, we defined a 229-bp domain that is 100% homologous in most H. pylori strains available in GenBank and also is specific for H. pylori. This sub-domain was then used to design (1) a set of high quality RT-PCR primers and probe that encompassed a 76-bp sequence and included at least two mismatches with other Helicobacter sp. 16S rRNA; and (2) in situ hybridization antisense probes. The sensitivity and specificity of the approaches were then demonstrated by using gastric biopsy specimens from patients and rhesus monkeys. This H. pylori-specific region of the 16S rRNA sequence is highly conserved among most H. pylori strains and allows specific detection, identification, and quantification of this bacterium in biological specimens.

Glutamine enhances glucose-induced mesangial cell proliferation.

The proliferation of mesangial cells (MC) in the presence of glutamine (0-20 mM) was determined in both low (5 mM) and high (25 mM) glucose-containing medium. Glutamine in a high glucose (HG) environment increased cell proliferation in a dose-dependent manner. Inhibition of glutamine:fructose 6-phosphate amidotransferase (GFAT) and of phosphodiesterase significantly reduced glutamine-induced proliferation. Supraphysiologic levels of glutamine increase MC proliferation in a HG milieu via GFAT and cAMP-dependent pathways, suggesting that glutamine could pose a risk for diabetic nephropathy.

TGF-beta-like transcriptional effects of thyroglobulin (Tg) in mouse mesangial cells.

TGF-beta-like activities of proteins unrelated to the cytokine could mimic its actions in fibrosis and cell proliferation. Thyroglobulin (Tg) has been identified as having a TGF-beta receptor (TGFbetaR)-binding activity and is deposited in the glomerulus in certain immune-complex diseases. The aim of the present study is to determine whether Tg can reproduce the transcriptional activity of TGF-beta1 in the mouse glomerular mesangial cell (MC), and to examine whether such activity is manifested through TGFbetaR. Real-time RT-PCR was employed to examine the effects of TGF-beta1 and bovine Tg on the expression of three genes (TGF-beta1, plasminogen activator inhibitor 1 [PAI-1], and Pax-8) regulated by TGF-beta1 in other cell types. In addition, a pentacosapeptide TGF-beta1 antagonist, beta(1)(25) (41-65) was employed to determine whether the transcriptional activity of Tg was mediated through the TGF-beta binding site on the TGFbetaR. A 6h exposure to TGF-beta1 resulted in increased TGF-beta1 and PAI-1 transcript, and a decrease in Pax-8. Similarly, a 6h exposure to Tg resulted in increases of about 5-fold in TGF-beta1 and PAI-1 mRNA and a decrease of 53% in Pax-8. In comparison with other proteins, Tg had the greatest positive effect on TGF-beta1 transcript levels. beta(1)(25) (41-65) significantly reduced the TGF-beta1-, but not the Tg-induced changes in TGF-beta1, PAI-1 and Pax-8 transcript levels. We conclude from these studies that Tg possesses a TGF-beta-mimetic transcriptional activity in the MC that is not mediated by its binding to TGFbetaR. These results suggest that Tg and other proteins could initiate glomerular injury by reproducing the actions of TGF-beta1 in the mesangial cell.

Increase of C-type natriuretic peptide expression by serum and platelet-derived growth factor-BB in human aortic smooth muscle cells is dependent on protein kinase C activation.

C-type natriuretic peptide (CNP) is produced by the vascular smooth muscle cells (SMCs) of injured and atherosclerotic arteries, in which it may exert autocrine control over SMCs by binding to its principal receptors, NPR-B and NPR-C, but few studies have examined the factors that regulate CNP expression in human SMCs. In the present report, we show that serum induces significant increases in both CNP and NPR-C transcript levels in human, but not rat SMCs in culture, and that pretreatment with either the general tyrosine kinase inhibitor genistein, the platelet-derived growth factor (PDGF) tyrosine kinase inhibitor AG 1296, or the protein kinase C (PKC) inhibitor GF109203X blocks most of the serum-induced increase in CNP. PDGF-BB also induced significant dose-dependent increases in CNP transcript that correlated temporally with the serum effect on CNP mRNA. Inhibition of several PDGF-BB signaling pathways downstream of receptor activation showed that PKC inhibition with GF109203X was almost as effective as genistein in abolishing the PDGF-BB-induced up-regulation of CNP mRNA. Furthermore, PKC activation by phorbol 12-myristate 13-acetate (PMA) produced an extremely high level of CNP mRNA that was abolished by GF109203X. Immunoreactive CNP was markedly increased in SMCs receiving 10% serum, 20 ng/ml PDGF-BB, or PMA, and was decreased in PDGF-treated and PMA-treated cells by AG 1296 and GF109203X, respectively. This report suggests that in humans, PDGF and other factors signaling through receptor tyrosine kinases and downstream activation of PKC could represent an important control for CNP expression in vascular smooth muscle.

Requirement for glutamine in the expression of alpha-actin and type IV collagen in mesangial cells.

The importance of glutamine for the synthesis of proteins of the extracellular matrix was investigated in cultured mesangial cells. Glutamine at 2 mM elicited an increase in smooth muscle cell alpha-actin, alpha(1)-type IV collagen and fibronectin transcripts (19.0-, 16.7-, and 4.3-fold, respectively) accompanied by an increase in alpha-actin stress fibres compared to cells grown in absence of glutamine. The specificity for the glutamine requirement is suggested by the fact that mRNA levels of tenascin were not altered by addition of glutamine. This suggests that glutamine is required for the expression of important proteins of the extracellular matrix in cultured mesangial cells.