Leptin and its receptor: can they help to differentiate chromophobe renal cell carcinoma from renal oncocytoma?

One of the challenges in differentiating chromophobe renal cell carcinoma (chRCC) from benign renal oncocytoma (RO) is overlapping morphology between the two subtypes. The aim of this study was to investigate the usefulness of expression of leptin (Ob) and its receptor (ObR) in discriminating chRCC from RO. Sections from paraffin-embedded, formalin-fixed tumour nephrectomy specimens of 45 patients, made up of 30 chRCC (15 eosinophilic variant and 15 non-eosinophilic variant) and 15 RO, were used in this study. Samples (30) of clear cell RCC (ccRCC), the most common histological subtype, were used to verify staining patterns found by others in our cohort of Australasian patients. Matched morphologically normal non-cancer kidney tissues were included for each specimen. Sections were batch-immunostained using antibodies against Ob and ObR. Stained sections were digitally scanned using Aperio ImageScope, and the expression pattern of Ob and ObR was studied. In this cohort, male to female ratio was 2:1; median age was 64 (45-88 years); and median tumour size was 3.8 cm (range 1.2-18 cm). There were 47 (62.7%) T1, seven T2, 20 T3 and one T4 stage RCC. Two patients with ccRCC presented with metastases. Nuclear expression of Ob was significantly higher in RO compared with chRCC. The increased nuclear expression of Ob in RO compared with chRCC may be a useful aid in the difficult histological differentiation of RO from chRCC, especially eosinophilic variants of chRCC.

Preparation and characterization of polyclonal antibodies against human chaperonin 10.

Early pregnancy factor (EPF) has been identified as an extracellular homologue of chaperonin 10 (Cpn10), a heat shock protein that functions within the cell as a molecular chaperone. Here, we report the production of polyclonal antibodies directed against several different regions of the human Cpn10 molecule and their application to specific protein quantitation and localization techniques. These antibodies will be valuable tools in further studies to elucidate the mechanisms underlying the differential spatial and temporal localization of EPF and Cpn10 and in studies to elucidate structure and function.

Inhibition of proliferation of HT-29 colon adenocarcinoma cells by carboxylate NSAIDs and their acyl glucuronides.

Many nonsteroidal anti-inflammatory drugs (NSAIDs) which have antiproliferative activity in colon cancer cells are carboxylate compounds forming acyl glucuronide metabolites. Acyl glucuronides are potentially reactive, able to hydrolyse, rearrange into isomers, and covalently modify proteins under physiological conditions. This study investigated whether the acyl glucuronides (and isomers) of the carboxylate NSAIDs diflunisal, zomepirac and diclofenac had antiproliferative activity on human adenocarcinoma HT-29 cells in culture. Included as controls were the carboxylate NSAIDs themselves, the non-carboxylate NSAID piroxicam, and the carboxylate non-NSAID valproate, as well as its acyl glucuronide and isomers. The compounds were incubated at 1-3000 microM with HT-29 cells for 24 hr, with [3H]-thymidine added for an additional 2 hr incubation. IC50 values were calculated from the concentration-inhibition response curves for thymidine uptake. The four NSAIDs inhibited thymidine uptake, with IC50 values about 200-500 microM. All of the NSAID acyl glucuronides (and isomers, tested in the case of diflunisal) showed antiproliferative activity broadly comparable to the parent drugs. This activity may stem from direct uptake of intact glucuronide/isomers followed by covalent modification of proteins critical in the cell replication process. However, hydrolysis during incubation and cellular uptake of liberated parent NSAID will play a role. In HT-29 cells incubated with zomepirac, covalently modified proteins in cytosol were detected by immunoblotting with a zomepirac antibody, suggesting that HT-29 cells do have the capacity to glucuronidate zomepirac. The anti-epileptic drug valproate had no effect on inhibition of thymidine uptake, though, surprisingly, its acyl glucuronide and isomers were active. The reasons for this are unclear at present.

Peritoneal homocysteine clearance is inefficient in peritoneal dialysis patients.

OBJECTIVES: To investigate the degree and the determinants of peritoneal homocysteine (Hcy) clearance and to compare measured Hcy clearance with the Hcy clearance predicted based on molecular weight (MW). DESIGN: Cross-sectional observational analysis. SETTING: Tertiary care institutional dialysis center. PATIENTS: Sixty-five stable peritoneal dialysis (PD) patients. OUTCOME MEASURES: Fasting blood and 24-hour pooled dialysate effluents were collected for determination of peritoneal clearances of Hcy (CpHcy), urea (CpUr), and creatinine (CpCr). The dialysate-to-plasma creatinine ratio at 4 hours (D/P Cr 4 h) and levels of red cell folate, B12, ferritin, and C-reactive protein (CRP) were measured concurrently. Observed CpHcy was compared with predicted clearance, based on Hcy plasma protein binding and the relative molecular weights of Hcy, urea, and creatinine. RESULTS: Plasma concentrations of Hcy averaged 24.6 +/- 1.1 micromol/L and were elevated above the upper limit of normal in 59 (91%) patients. The mean dialysate concentration of Hcy was 2.9 +/- 0.3 micromol/L, equating to a daily peritoneal elimination of 34.6 +/- 3.6 micromol. Observed CpHcy was closely approximated by predicted CpHcy (8.7 +/- 0.6 L/week/1.73 m2 vs 9.0 +/- 0.3 L/week/1.73 m2 respectively, p = 0.55). Patients maintained on automated PD (n = 5) had a CpHcy similar to that of patients treated with continuous ambulatory peritoneal dialysis (8.9 +/- 1.0 L/week/1.73 m2 vs 8.7 +/- 0.6 L/week/1.73 m2, p = 0.92). The CpHcy was significantly correlated with C-reactive protein (CRP), D/P creatinine, CpUr, CpCr, and peritoneal protein loss, but not with plasma Hcy, albumin, B12, ferritin, age, dialysis duration, peritonitis episodes, or daily dialysate effluent volume. By multivariate analysis, the only variables that remained significant independent predictors of CpHcy were CRP and D/P Cr 4 h. High and high-average transporters had a higher CpHcy than low and low-average transporters (9.7 +/- 0.8 L/week/1.73 m2 vs 7.0 +/- 0.7 L/week/1.73 m2, p < 0.05), despite comparably elevated plasma Hcy concentrations [25.2 +/- 1.5 micromol/L vs 23.4 +/- 1.6 micromol/L, p = nonsignificant (NS)]. CONCLUSIONS: Elevated plasma concentrations of Hcy are not efficiently reduced by PD. The relatively low peritoneal clearance of Hcy is largely accounted for by a high degree of plasma protein binding and is significantly influenced by peritoneal membrane permeability.

Pathway-selective antagonism of proteinase activated receptor 2.

BACKGROUND AND PURPOSE: Proteinase activated receptor 2 (PAR2) is a GPCR associated with inflammation, metabolism and disease. Clues to understanding how to block PAR2 signalling associated with disease without inhibiting PAR2 activation in normal physiology could be provided by studies of biased signalling. EXPERIMENTAL APPROACH: PAR2 ligand GB88 was profiled for PAR2 agonist and antagonist properties by several functional assays associated with intracellular G-protein-coupled signalling in vitro in three cell types and with PAR2-induced rat paw oedema in vivo. KEY RESULTS: In HT29 cells, GB88 was a PAR2 antagonist in terms of Ca(2+) mobilization and PKC phosphorylation, but a PAR2 agonist in attenuating forskolin-induced cAMP accumulation, increasing ERK1/2 phosphorylation, RhoA activation, myosin phosphatase phosphorylation and actin filament rearrangement. In CHO-hPAR2 cells, GB88 inhibited Ca(2+) release, but activated G(i/o) and increased ERK1/2 phosphorylation. In human kidney tubule cells, GB88 inhibited cytokine secretion (IL6, IL8, GM-CSF, TNF-α) mediated by PAR2. A rat paw oedema induced by PAR2 agonists was also inhibited by orally administered GB88 and compared with effects of locally administered inhibitors of G-protein coupled pathways. CONCLUSIONS AND IMPLICATIONS: GB88 is a biased antagonist of PAR2 that selectively inhibits PAR2/G(q/11)/Ca(2+)/PKC signalling, leading to anti-inflammatory activity in vivo, while being an agonist in activating three other PAR2-activated pathways (cAMP, ERK, Rho) in human cells. These findings highlight opportunities to design drugs to block specific PAR2-linked signalling pathways in disease, without blocking beneficial PAR2 signalling in normal physiology, and to dissect PAR2-associated mechanisms of disease in vivo.

Delayed administration of darbepoetin or erythropoietin protects against ischemic acute renal injury and failure.

Administration of human recombinant erythropoietin (EPO) at time of acute ischemic renal injury (IRI) inhibits apoptosis, enhances tubular epithelial regeneration, and promotes renal functional recovery. The present study aimed to determine whether darbepoetin-alfa (DPO) exhibits comparable renoprotection to that afforded by EPO, whether pro or antiapoptotic Bcl-2 proteins are involved, and whether delayed administration of EPO or DPO 6 h following IRI ameliorates renal dysfunction. The model of IRI involved bilateral renal artery occlusion for 45 min in rats (N = 4 per group), followed by reperfusion for 1-7 days. Controls were sham-operated. Rats were treated at time of ischemia or sham operation (T0), or post-treated (6 h after the onset of reperfusion, T6) with EPO (5000 IU/kg), DPO (25 mug/kg), or appropriate vehicle by intraperitoneal injection. Renal function, structure, and immunohistochemistry for Bcl-2, Bcl-XL, and Bax were analyzed. DPO or EPO at T0 significantly abrogated renal dysfunction in IRI animals (serum creatinine for IRI 0.17 +/- 0.05 mmol/l vs DPO-IRI 0.08 +/- 0.03 mmol/l vs EPO-IRI 0.04 +/- 0.01 mmol/l, P = 0.01). Delayed administration of DPO or EPO (T6) also significantly abrogated subsequent renal dysfunction (serum creatinine for IRI 0.17 +/- 0.05 mmol/l vs DPO-IRI 0.06 +/- 0.01 mmol/l vs EPO-IRI 0.03 +/- 0.03 mmol/l, P = 0.01). There was also significantly decreased tissue injury (apoptosis, P < 0.05), decreased proapoptotic Bax, and increased regenerative capacity, especially in the outer stripe of the outer medulla, with DPO or EPO at T0 or T6. These results reaffirm the potential clinical application of DPO and EPO as novel renoprotective agents for patients at risk of ischemic acute renal failure or after having sustained an ischemic renal insult.

Galactosamine induced hepatitis induces a reduction in hepatocyte epidermal growth factor receptors.

The rapid regenerative response of the rat liver to partial hepatectomy is associated with a decline in liver epidermal growth factor receptor numbers which implies that ligand epidermal growth factor receptor interactions maybe important in initiating and/or modulating this process. The proliferative process in toxic hepatitis (where in contrast with partial hepatectomy the majority of hepatocytes have been exposed to damaging influences) has been less widely investigated. We studied the DNA synthetic response of rat livers to toxic injury induced by a 350 or 800 mg/kg ip injection of galactosamine and that caused by 70% hepatectomy, comparing the changes in epidermal growth factor receptor status. Both resulted in down regulation of epidermal growth factor receptors, suggesting similar ligand epidermal growth factor receptor binding occurs during the proliferative response after galactosamine administration and after partial hepatectomy. In vitro studies on isolated hepatocytes showed that epidermal growth factor receptor down regulation was not a direct effect of galactosamine on hepatocyte membranes.

Comparative effects of epidermal growth factor, an insulin-glucagon combination, and a hepatocyte growth factor preparation on epidermal growth factor receptors.

We investigated the changes in cell surface epidermal growth factor (EGF) receptors in the liver after partial hepatectomy, and in primary adult rat hepatocyte cultures following stimulation with either EGF, or a preparation of hepatocyte growth factor, or an insulin-glucagon combination. We confirmed a reduction in EGF receptors on hepatocytes after partial hepatectomy and a rapid down-regulation of EGF receptors on normal hepatocytes in vitro following exposure to EGF. Insulin and glucagon and hepatocyte growth factor, whilst initiating hepatocyte DNA synthesis, had only slight effects on their EGF binding capacity and EGF-receptor affinity. These results indicate that changes in cell membranes early in proliferation have only non-specific effects on EGF receptors, and, therefore, support the role of ligand binding to the EGF receptor as an important component of hepatocyte proliferation in vivo.

Down regulation of epidermal growth factor receptors in liver proliferation induced by a mixture of triiodothyronine, amino acids, glucagon, and heparin (TAGH).

This study investigated the mechanisms by which TAGH solution (a mixture of triiodothyronine, amino acids, glucagon, and heparin) induces DNA synthesis in hepatocytes in the liver of intact rats, with particular reference to events at the epidermal growth factor (EGF) receptor. Both partial hepatectomy and infusion of TAGH stimulated DNA synthesis at 24 hours and both procedures resulted in a reduction of EGF receptors assessed in plasma membranes isolated from rat liver at this time. In cell cultures, while EGF strongly stimulated DNA synthesis and started EGF receptor down regulation, TAGH had only a minor effect (1.5 x basal) on DNA synthesis and did not interact with or down regulate the EGF receptor. Membrane phosphorylation studies, however, showed that TAGH induced phosphorylation of tyrosine residues in the EGF receptor. The in vivo action of TAGH seems to entail recruitment of similar changes in the EGF receptor to those that occur after partial hepatectomy.

p53 gene in hepatocellular carcinomas from Australia.

The p53 protein is now well established as a crucial player in regulation of cell growth. Mutations arising in the coding sequences of its gene have been demonstrated in a wide variety of human tumors, including hepatocellular carcinoma (HCC). Our previous studies have shown that codon 249 mutations, the most common mutation of the p53 gene in HCCs, did not occur in our group of patients. To examine the prevalence of p53 mutations in other areas of the p53 gene, PCR and direct sequencing were carried out on these samples covering the four highly conserved regions of the gene between exons 5 and 8. Liver samples were obtained from both HBV+ and HBV- patients in a variety of ethnic groups. Primers to the flanking regions of exon 5, 6, 7, and 8 were used in PCR to amplify these exons. Following purification, the products were sequenced in both directions by cycle sequencing. In 15 HCCs examined, no mutations in these exons of the p53 gene were found. This suggests a less important role for p53 in development of HCC in this group of patients than in patients from other areas of the world.

Effect of in vivo administration of an antibody to epidermal growth factor on the rapid increase in DNA synthesis induced by partial hepatectomy in the rat.

Recent reports indicate that transforming growth factor alpha (TGF-alpha) is produced within the liver and acts as the natural ligand of the epidermal growth factor (EGF) receptor causing the EGF receptor down regulation and the hepatocyte proliferation observed after partial hepatectomy. The reported phenomenon that an antibody to EGF inhibits the regenerative response to partial hepatectomy was therefore re-investigated. The IgG fraction of an anti-rat EGF antibody was injected intravenously at the time of partial hepatectomy, and its effects on regenerative DNA synthesis were compared with those of non-immune IgG. Injection of IgG reduced the DNA synthetic response to partial hepatectomy, assessed 24 hours after resection by 3H-thymidine incorporation, but the effects of normal and anti-EGF IgG were not statistically different, despite the presence of excess anti-EGF IgG in the circulation throughout the experimental period. However, anti-EGF IgG could completely block the proliferative response of hepatocytes in culture to EGF. These results support the suggestion that EGF is not the major mediator of hepatocyte DNA synthesis in the early stages of liver regeneration (less than 24 hours).

Dose-dependent effects of fentanyl on indomethacin-induced gastric damage.

Whilst developing a rat model for studies of gastric protection, we noticed that the anaesthetic agent 'Hypnorm', containing the opiate fentanyl 0.315 mg/ml and the butyrophenone fluanisone 10 mg/ml, was itself protective against indomethacin-induced damage: unrestrained animals given indomethacin (20 mg/kg) subcutaneously had an ulcer score of 9 +/- 1 mm2, compared with 1 +/- 1 mm2 in animals pre-treated with Hypnorm (0.8 ml/kg) and then given indomethacin (p less than 0.01). Further investigation showed this effect to be due to fentanyl-inhibiting gastric acid secretion: doses of fentanyl (90 and 180 micrograms/kg) which decreased indomethacin-induced damage also caused a rise in intragastric pH from 2.7 +/- 0.6 in controls to 5.1 +/- 0.8 and 5.0 +/- 0.8, respectively. However, the response of fentanyl varied depending on the dose given: fentanyl, 3.6 micrograms/kg did not affect indomethacin-induced damage, 8 +/- 2 vs. 9 +/- 1 mm2; fentanyl, 18 micrograms/kg potentiated damage, 15 +/- 4 mm2 (p less than 0.05), whereas fentanyl, 90 micrograms/kg and 180 micrograms/kg decreased damage, 2 +/- 1 mm2 and 0.1 +/- 0.1 mm2, respectively (p less than 0.01). Neither the butyrophenone haloperidol (8.3 mg/kg) nor the alpha-adrenergic receptor antagonist phenoxybenzamine (3 mg/kg) protected against indomethacin-induced damage. We conclude that fentanyl affects intragastric pH and can both potentiate and protect against indomethacin-induced damage. Furthermore, the potentiation of gastric damage by fentanyl occurred at doses similar to those used for human anesthesia, so clinical studies are suggested.

Enalaprilat directly ameliorates in vitro cyclosporin nephrotoxicity in human tubulo-interstitial cells.

BACKGROUND/AIMS: Several recent studies have suggested that angiotensin-converting enzyme (ACE) inhibitors ameliorate chronic cyclosporin A (CyA) tubulo-interstitial disease by mechanisms independent of their antihypertensive effects. The aim of the present study was to determine whether ACE inhibition exerts a direct beneficial effect on the tubulo-interstitium in an in vitro model of chronic CyA nephropathy. METHODS: Primary cultures of human proximal tubular cells (PTC) and renal cortical fibroblasts (CF) were exposed for 24 h to CyA in the presence or absence of enalaprilat. Parameters of tubulo-interstitial nephrotoxicity were then measured including collagen synthesis (proline incorporation), tubular viability and function (thymidine incorporation, lactate dehydrogenase release, and apical sodium-hydrogen exchange), and secretion of insulin-like growth factor I, transforming growth factor beta 1 (TGFbeta1), and platelet-derived growth factor. RESULTS: CyA promoted CF collagen synthesis, PTC cytotoxicity (suppressed viability, growth and sodium transport), and tubulo-interstitial fibrogenic cytokine release (CF secretion of insulin-like growth factor I and PTC secretion of TGFbeta1 and platelet-derived growth factor). Enalaprilat completely reversed the stimulatory effects of CyA on CF collagen synthesis (CyA + enalaprilat 6.40 +/- 0.50% vs. CyA alone 8.33 +/- 0.56% vs. control 6.57 +/- 0.62% vs. enalaprilat alone 5.55 +/- 0.93%, p < 0.05) and PTC secretion of TGFbeta1 (0.71 +/- 0.11, 1.13 +/- 0.09, 0.89 +/- 0.07, and 0.67 +/- 0.09 ng/mg protein/day, respectively, p < 0.05). However, the other manifestations of CyA toxicity were not significantly reversed by concomitant enalaprilat administration. CONCLUSIONS: ACE inhibition directly prevents CyA-induced interstitial fibrosis, but not proximal tubule cytotoxicity, independently of haemodynamic and systemic renin-angiotensin system effects. Renoprotection may be partially afforded by directly preventing the tubular secretion of TGFbeta1.

Dimethyl sulphoxide induces a reduced growth rate, altered cell morphology and increased epidermal-growth-factor binding in Hep G2 cells.

Culture of Hep G2 cells in medium containing 2% (v/v) dimethyl sulphoxide (DMSO) resulted in a slowing of growth and a marked change in morphological appearance. By day 6, cultures containing DMSO had one-third the number of cells compared with parallel control cultures. Measurement of 125I-epidermal-growth-factor (EGF) binding to DMSO-treated cells revealed a striking time-dependent elevation in specific EGF binding to their cell surface. Increased binding was detectable within 24 h of the start of DMSO treatment, reaching, by 6 days, levels almost 25 times greater than those for control cells. Addition of EGF to DMSO-treated cells caused a rapid down-regulation of the EGF receptor, but did not alter their proliferation rate. Slowing of growth by other means, such as serum starvation, growth to confluence or culture in the presence of sodium butyrate, did not affect 125I-EGF binding, indicating a specific effect of DMSO on these cells.

Gastric output of pancreatic secretory trypsin inhibitor is increased by misoprostol.

Pancreatic secretory trypsin inhibitor (PSTI) is a potent protease inhibitor that also has growth promoting activity. It has recently been identified in the foveolar cells of the stomach, which secrete mucus. We examined the effects of the prostaglandin E1 analogue misoprostol on gastric PSTI output. Seven normal volunteers took part. An initial period of gastric aspiration was followed by four 40 minute periods of gastric perfusion at 5 ml/minute of: 0.14 mol/l saline, 0.17 mmol/l bicarbonate, bicarbonate with misoprostol 400 micrograms, and then bicarbonate again. All perfusates contained polyethylene glycol 4000 as a marker. Misoprostol increased median gastric secretion of PSTI from 11 to 33 micrograms/hour (p less than 0.05), producing concentrations in gastric juice six times higher than those found in jejunal juice and about 1/30 of the values seen in pancreatic juice. Median mucus secretion increased to a lesser extent from 29 to 38 mg/hour during misoprostol. There was no change in intragastric concentrations of protein or of epidermal growth factor during infusion of misoprostol. Infusion of pentagastrin (6 micrograms/kg/hour) had no effect on gastric secretion of mucus, PSTI, or protein. Human gastric mucus was degraded on incubation with trypsin in vitro and this was prevented by the addition of PSTI. These results suggest that gastric PSTI may protect the gastric mucus layer against refluxed pancreatic proteases. Increased output of PSTI during microprostol may contribute to the protective effect of this drug.

Human adipose tissue endothelial cells promote preadipocyte proliferation.

Adipogenesis is preceded by development of a microvascular network, and optimal functioning of adipose tissue as an energy store and endocrine organ is dependent on extensive vascularization. We have examined the role of endothelial cell-derived factors that influence the proliferation of human preadipocytes. Microvascular endothelial cells and preadipocytes were isolated from human omental and subcutaneous adipose tissue biopsies by use of a developed procedure of collagenase digest, immunoselection, and differential trypsinization. Conditioned medium from microvascular endothelial cell cultures promoted the proliferation of preadipocytes (P = <0.001) and (to a lesser extent) other cell types. No depot-specific differences in mitogenic capacity of microvascular endothelial cell medium or of preadipocyte response were observed. These results indicate that adipose tissue endothelial cells secrete soluble adipogenic factor(s).