Prognostic value of aldo-keto reductase family 1 member B10 (AKR1B10) in digestive system cancers: A meta-analysis

Background:Numbers of studies have reported that the expression of aldo-keto reductase family 1 member B10 (AKR1B10) is abnormal in digestive system cancers, and could be used as a prognostic biomarker. However, the results are argued. Therefore, we conduct a meta-analysis to comprehensively evaluate the prognostic value of high AKR1B10 expression for overall survival (OS), disease specific survival (DSS), and disease-free survival/recurrence-free survival (DFS/PFS) in digestive system cancers.Methods:Hazard ratios (HRs) with its 95% confidence intervals (CIs) were calculated to assess the prognostic value of AKR1B10 by using the random effects model. The STATA version 12.0 software were used to perform all the analyses.Results:Eleven articles including 1428 patients involved in this meta-analysis. The pooled analysis suggested that high AKR1B10 expression was not associated with OS (HR: 1.18; 95% CI: 0.69–2.00) and DFS/PFS (HR: 1.08, 95% CI: 0.67–1.76) in digestive system cancers. However, Further analysis revealed that high AKR1B10 expression indicated poor OS in oral squamous cell carcinomas (OSCC) (HR: 2.92, 95% CI: 1.86–4.58) and favorable DSS in hepatocellular carcinoma (HCC) (HR: 0.71, 95% CI: 0.52–0.97).Conclusions:The prognostic value of high AKR1B10 expression varied in different types of digestive system cancers. Further studies exploring the prognostic role of AKR1B10 in digestive system cancers are needed.     

Pretreatment AKR1B10 expression predicts the risk of hepatocellular carcinoma development after hepatitis C virus eradication

AIM To clarify the association between aldo-keto reductase family 1 member B10(AKR1B10) expression and hepatocarcinogenesis after hepatitis C virus eradication.METHODS In this study,we enrolled 303 chronic hepatitis C patients who had achieved sustained virological response(SVR) through interferon-based antiviral therapy. Pretreatment AKR1B10 expression in the liver was immunohistochemically assessed and quantified as a percentage of positive staining area by using image-analysis software. A multivariate Cox analysis was used to estimate the hazard ratios(HRs) of AKR1B10 expression for hepatocellular carcinoma(HCC) development after achieving SVR. The cumulative incidences of HCC development were evaluated using Kaplan-Meier analysis and the log-rank test.RESULTS Of the 303 chronic hepatitis C patients,153(50.5%) showed scarce hepatic AKR1B10 expression,quantified as 0%,which was similar to the expression in control normal liver tissues. However,the remaining 150 patients(49.5%) exhibited various degrees of AKR1B10 expression in the liver,with a maximal AKR1B10 expression of 73%. During the median follow-up time of 3.6 years(range 1.0-10.0 years),8/303 patients developed HCC. Multivariate analysis revealed that only high AKR1B10 expression(≥ 8%) was an independent risk factor for HCC development(HR = 15.4,95%CI: 1. 8- 1 3 2. 5,P = 0. 0 1 2). T h e 5- y e a r c u m u l a t i v e incidences of HCC development were 13.7% and 0.5% in patients with high and low AKR1B10 expression,respectively(P 0.001). During the follow-up period after viral eradication,patients expressing high levels of AKR1B10 expressed markedly higher levels of alanine aminotransferase and α-fetoprotein than did patients exhibiting low AKR1B10 expression.CONCLUSION Chronic hepatitis C patients expressing high levels of hepatic AKR1B10 had an increased risk of HCC development even after SVR.     

Oligomerization domain-directed reassembly of active dihydrofolate reductase from rationally designed fragments

Reassembly of enzymes from peptide fragments has been used as a strategy for understanding the evolution, folding, and role of individual subdomains in catalysis and regulation of activity. We demonstrate an oligomerization-assisted enzyme reassembly strategy whereby fragments are covalently linked to independently folding and interacting domains whose interactions serve to promote efficient refolding and complementation of fragments, forming active enzyme. We show that active murine dihydrofolate reductase (E.C. 1.5.1.3) can be reassembled from complementary N- and C-terminal fragments when fused to homodimerizing GCN4 leucine zipper-forming sequences as well as heterodimerizing protein partners. Reassembly is detected by an in vivo selection assay in Escherichia coli and in vitro. The effects of mutations that disrupt fragment affinity or enzyme activity were assessed. The steady–state kinetic parameters for the reassembled mutant (Phe-31 → Ser) were determined; they are not significantly different from the full-length mutant. The strategy described here provides a general approach for protein dissection and domain swapping studies, with the capacity both for rapid in vivo screening as well as in vitro characterization. Further, the strategy suggests a simple in vivo enzyme-based detection system for protein–protein interactions, which we illustrate with two examples: ras–GTPase and raf–ras-binding domain and FK506-binding protein-rapamycin complexed with the target of rapamycin TOR2.     

Glutaredoxin function for the carboxyl-terminal domain of the plant-type 5′-adenylylsulfate reductase

5′-Adenylylsulfate (APS) reductase (EC 1.8.99.-) catalyzes the reduction of activated sulfate to sulfite in plants. The evidence presented here shows that a domain of the enzyme is a glutathione (GSH)-dependent reductase that functions similarly to the redox cofactor glutaredoxin. The APR1 cDNA encoding APS reductase from Arabidopsis thaliana is able to complement the cysteine auxotrophy of an Escherichia coli cysH [3′-phosphoadenosine-5′-phosphosulfate (PAPS) reductase] mutant, only if the E. coli strain produces glutathione. The purified recombinant enzyme (APR1p) can use GSH efficiently as a hydrogen donor in vitro, showing a K_m[GSH] of ≈0.6 mM. Gene dissection was used to express separately the regions of APR1p from amino acids 73–327 (the R domain), homologous with microbial PAPS reductase, and from amino acids 328–465 (the C domain), homologous with thioredoxin. The R and C domains alone are inactive in APS reduction, but the activity is partially restored by mixing the two domains. The C domain shows a number of activities that are typical of E. coli glutaredoxin rather than thioredoxin. Both the C domain and APR1p are highly active in GSH-dependent reduction of hydroxyethyldisulfide, cystine, and dehydroascorbate, showing a K_m[GSH] in these assays of ≈1 mM. The R domain does not show these activities. The C domain is active in GSH-dependent reduction of insulin disulfides and ribonucleotide reductase, whereas APR1p and R domain are inactive. The C domain can substitute for glutaredoxin in vivo as demonstrated by complementation of an E. coli mutant, underscoring the functional similarity between the two enzymes.     

Nonerythropoietic, tissue-protective peptides derived from the tertiary structure of erythropoietin

Erythropoietin (EPO), a member of the type 1 cytokine superfamily, plays a critical hormonal role regulating erythrocyte production as well as a paracrine/autocrine role in which locally produced EPO protects a wide variety of tissues from diverse injuries. Significantly, these functions are mediated by distinct receptors: hematopoiesis via the EPO receptor homodimer and tissue protection via a heterocomplex composed of the EPO receptor and CD131, the β common receptor. In the present work, we have delimited tissue-protective domains within EPO to short peptide sequences. We demonstrate that helix B (amino acid residues 58–82) of EPO, which faces the aqueous medium when EPO is bound to the receptor homodimer, is both neuroprotective in vitro and tissue protective in vivo in a variety of models, including ischemic stroke, diabetes-induced retinal edema, and peripheral nerve trauma. Remarkably, an 11-aa peptide composed of adjacent amino acids forming the aqueous face of helix B is also tissue protective, as confirmed by its therapeutic benefit in models of ischemic stroke and renal ischemia–reperfusion. Further, this peptide simulating the aqueous surface of helix B also exhibits EPO's trophic effects by accelerating wound healing and augmenting cognitive function in rodents. As anticipated, neither helix B nor the 11-aa peptide is erythropoietic in vitro or in vivo. Thus, the tissue-protective activities of EPO are mimicked by small, nonerythropoietic peptides that simulate a portion of EPO's three-dimensional structure.     

Serum AKR1B10 predicts the risk of hepatocellular carcinoma – A retrospective single-center study

ObjectivesAKR1B10, first cloned from liver cancer tissues, has recently been reported to be up-regulated significantly in hepatocellular carcinoma (HCC) tissues, but the relationship between serum level of AKR1B10 and the risk of HCC is not understood.Methods170 HCC patients and 120 health donors from October 2014 to March 2017 were recruited in the affiliated hospital of Guilin Medical University. Serum AKR1B10 in all cases were detected and in 30 HCC patients were analyzed preoperatively and postoperatively by Time-resolved fluoroimmunoassay.ResultsThe level of serum AKR1B10 was significantly higher in HCC patients (1800.24 ± 2793.79) than in health donors (129.34 ± 194.129), and downregulation of serum AKR1B10 in HCC patients was observed after hepatectomy. When samples were grouped according to the serum level of AKR1B10 (≥232.7 pg/ml), serum AKR1B10 positively correlated to serum AFP (χ² = 6.295, P = 0.012), ALT (χ² = 18.803, P = 0.000), AST (χ² = 33.421, P = 0.000), tumor nodule number (χ² = 6.777, P = 0.009), cirrhosis (χ² = 43.458, P = 0.000), and tumor size (χ² = 6.042, P = 0.014) in the Chi-square test.ConclusionsDiagnosis of HCC could be improved using the both predictors of serum AKR1B10 and AFP. AKR1B10 was thus considered to be a new serological biomarker for HCC.     

Interleukin 12 and B7-1 costimulatory molecule expressed by an adenovirus vector act synergistically to facilitate tumor regression

Stimulation of antitumor immune mechanisms is the primary goal of cancer immunotherapy, and accumulating evidence suggests that effective alteration of the host–tumor relationship involves immunomodulating cytokines and also the presence of costimulatory molecules. To examine the antitumor effect of direct in vivo gene transfer of murine interleukin 12 (IL-12) and B7-1 into tumors, we developed an adenovirus (Ad) vector, AdIL12–B7-1, that encodes the two IL-12 subunits in early region 1 (E1) and the B7-1 gene in E3 under control of the murine cytomegalovirus promoter. This vector expressed high levels of IL-12 and B7-1 in infected murine and human cell lines and in primary murine tumor cells. In mice bearing tumors derived from a transgenic mouse mammary adenocarcinoma, a single intratumoral injection with a low dose (2.5 × 10⁷ pfu/mouse) of AdIL12–B7-1 mediated complete regression in 70% of treated animals. By contrast, administration of a similar dose of recombinant virus encoding IL-12 or B7-1 alone resulted in only a delay in tumor growth. Interestingly, coinjection of two different viruses expressing either IL-12 or B7-1 induced complete tumor regression in only 30% of animals treated at this dose. Significantly, cured animals remained tumor free after rechallenge with fresh tumor cells, suggesting that protective immunity had been induced by treatment with AdIL12–B7-1. These results support the use of Ad vectors as a highly efficient delivery system for synergistically acting molecules and show that the combination of IL-12 and B7-1 within a single Ad vector might be a promising approach for in vivo cancer therapy.     

Carboxylic acid reductase is a versatile enzyme for the conversion of fatty acids into fuels and chemical commodities

Aliphatic hydrocarbons such as fatty alcohols and petroleum-derived alkanes have numerous applications in the chemical industry. In recent years, the renewable synthesis of aliphatic hydrocarbons has been made possible by engineering microbes to overaccumulate fatty acids. However, to generate end products with the desired physicochemical properties (e.g., fatty aldehydes, alkanes, and alcohols), further conversion of the fatty acid is necessary. A carboxylic acid reductase (CAR) from Mycobacterium marinum was found to convert a wide range of aliphatic fatty acids (C₆–C₁₈) into corresponding aldehydes. Together with the broad-substrate specificity of an aldehyde reductase or an aldehyde decarbonylase, the catalytic conversion of fatty acids to fatty alcohols (C₈–C₁₆) or fatty alkanes (C₇–C₁₅) was reconstituted in vitro. This concept was applied in vivo, in combination with a chain-length-specific thioesterase, to engineer Escherichia coli BL21(DE3) strains that were capable of synthesizing fatty alcohols and alkanes. A fatty alcohol titer exceeding 350 mg·L⁻¹ was obtained in minimal media supplemented with glucose. Moreover, by combining the CAR-dependent pathway with an exogenous fatty acid-generating lipase, natural oils (coconut oil, palm oil, and algal oil bodies) were enzymatically converted into fatty alcohols across a broad chain-length range (C₈–C₁₈). Together with complementing enzymes, the broad substrate specificity and kinetic characteristics of CAR opens the road for direct and tailored enzyme-catalyzed conversion of lipids into user-ready chemical commodities.     

Aldo‐keto reductase family 1 member B10 is associated with hepatitis B virus‐related hepatocellular carcinoma risk

Aim

Recent reports have indicated that aldo‐keto reductase family 1 member B10 (AKR1B10), a cancer‐related oxidoreductase, was upregulated in some chronic liver diseases. However, few studies have reported AKR1B10 expression in chronic hepatitis B virus (HBV)‐infected patients. The aim of the present study was to analyze AKR1B10 expression and its relevance on hepatocellular carcinoma (HCC) development in patients with chronic HBV infection.

Methods

Expression of AKR1B10 in the liver of 119 chronic HBV‐infected patients was assessed and quantified immunohistochemically. A multivariate Cox model was used to estimate the hazard ratios of AKR1B10 expression for HCC development. The cumulative incidences of HCC were evaluated using Kaplan–Meier analysis.

Results

Expression of AKR1B10 in the study cohort ranged from 0% to 84%. During the median follow‐up time (6.2 years), 13 patients developed HCC. Multivariate analysis revealed that high AKR1B10 expression (≥15%) was an independent risk factor for HCC (hazard ratio, 10.8; 95% confidence interval, 3.0–38.6; P < 0.001). The 5‐year cumulative incidences of HCC were 20.6% and 2.6% in patients with high and low AKR1B10 expression, respectively (P < 0.001). Patients with high AKR1B10 expression had significantly higher alanine aminotransferase levels during follow‐up than those with low expression, even though antiviral treatment decreased HBV‐DNA levels in both groups.

Conclusion

Chronic HBV‐infected patients with high hepatic AKR1B10 expression had an increased risk of HCC development. This suggests that AKR1B10 upregulation might play a role in the early stages of HBV‐related hepatocarcinogenesis.

     

Discovery of a human liver glycogen phosphorylase inhibitor that lowers blood glucose in vivo

An inhibitor of human liver glycogen phosphorylase a (HLGPa) has been identified and characterized in vitro and in vivo. This substance, [R-(R*,S*)]-5-chloro-N-[3-(dimethylamino)-2-hydroxy-3-oxo-1-(phenylmethyl)propyl]-1H-indole-2-carboxamide (CP-91149), inhibited HLGPa with an IC₅₀ of 0.13 μM in the presence of 7.5 mM glucose. CP-91149 resembles caffeine, a known allosteric phosphorylase inhibitor, in that it is 5- to 10-fold less potent in the absence of glucose. Further analysis, however, suggests that CP-91149 and caffeine are kinetically distinct. Functionally, CP-91149 inhibited glucagon-stimulated glycogenolysis in isolated rat hepatocytes (P < 0.05 at 10–100 μM) and in primary human hepatocytes (2.1 μM IC₅₀). In vivo, oral administration of CP-91149 to diabetic ob/ob mice at 25–50 mg/kg resulted in rapid (3 h) glucose lowering by 100–120 mg/dl (P < 0.001) without producing hypoglycemia. Further, CP-91149 treatment did not lower glucose levels in normoglycemic, nondiabetic mice. In ob/ob mice pretreated with ¹⁴C-glucose to label liver glycogen, CP-91149 administration reduced ¹⁴C-glycogen breakdown, confirming that glucose lowering resulted from inhibition of glycogenolysis in vivo. These findings support the use of CP-91149 in investigating glycogenolytic versus gluconeogenic flux in hepatic glucose production, and they demonstrate that glycogenolysis inhibitors may be useful in the treatment of type 2 diabetes.     

Targeting the spliceosome in chronic lymphocytic leukemia with the macrolides FD-895 and pladienolide-B

RNA splicing plays a fundamental role in human biology. Its relevance in cancer is rapidly emerging as demonstrated by spliceosome mutations that determine the prognosis of patients with hematologic malignancies. We report studies using FD-895 and pladienolide-B in primary leukemia cells derived from patients with chronic lymphocytic leukemia and leukemia-lymphoma cell lines. We found that FD-895 and pladienolide-B induce an early pattern of mRNA intron retention – spliceosome modulation. This process was associated with apoptosis preferentially in cancer cells as compared to normal lymphocytes. The pro-apoptotic activity of these compounds was observed regardless of poor prognostic factors such as Del(17p), TP53 or SF3B1 mutations and was able to overcome the protective effect of culture conditions that resemble the tumor microenvironment. In addition, the activity of these compounds was observed not only in vitro but also in vivo using the A20 lymphoma murine model. Overall, these findings give evidence for the first time that spliceosome modulation is a valid target in chronic lymphocytic leukemia and provide an additional rationale for the development of spliceosome modulators for cancer therapy.     

Differential effects of rapamycin and retinoic acid on expansion,stability and suppressive qualities of human CD4+CD25+FOXP3+ T regulatory cell subpopulations

Adoptive transfer of ex vivo expanded CD4⁺CD25⁺FOXP3⁺ regulatory T cells is a successful therapy for autoimmune diseases and transplant rejection in experimental models. In man, equivalent manipulations in bone marrow transplant recipients appear safe, but questions regarding the stability of the transferred regulatory T cells during inflammation remain unresolved. In this study, protocols for the expansion of clinically useful numbers of functionally suppressive and stable human regulatory T cells were investigated. Regulatory T cells were expanded in vitro with rapamycin and/or all-trans retinoic acid and then characterized under inflammatory conditions in vitro and in vivo in a humanized mouse model of graft-versus-host disease. Addition of rapamycin to regulatory T-cell cultures confirms the generation of high numbers of suppressive regulatory T cells. Their stability was demonstrated in vitro and substantiated in vivo. In contrast, all-trans retinoic acid treatment generates regulatory T cells that retain the capacity to secrete IL-17. However, combined use of rapamycin and all-trans retinoic acid abolishes IL-17 production and confers a specific chemokine receptor homing profile upon regulatory T cells. The use of purified regulatory T-cell subpopulations provided direct evidence that rapamycin can confer an early selective advantage to CD45RA⁺ regulatory T cells, while all-trans retinoic acid favors CD45RA⁻ regulatory T-cell subset. Expansion of regulatory T cells using rapamycin and all-trans retinoic acid drug combinations provides a new and refined approach for large-scale generation of functionally potent and phenotypically stable human regulatory T cells, rendering them safe for clinical use in settings associated with inflammation.     

High Expression of Aldo-Keto Reductase 1B10 Is an Independent Predictor of Favorable Prognosis in Patients with Hepatocellular Carcinoma

Background/Aims

Upregulation of aldo-keto reductase 1B10 (AKR1B10) through the mitogenic activator protein-1 signaling pathway might promote hepatocarcinogenesis and tumor progression. The goal of this study was to evaluate the prognostic significance of AKR1B10 protein expression in patients with hepatocellular carcinoma after surgery.

Methods

A tissue microarray was used to detect the expression level of AKR1B10 protein in tumors from 255 patients with hepatocellular carcinoma who underwent curative hepatectomy. The impact of AKR1B10 expression on the survival of patients was analyzed. The median follow-up period was 119.8 months.

Results

High AKR1B10 protein expression was observed in 125 of the 255 patients with hepatocellular carcinoma (49.0%). High AKR1B10 expression was significantly associated with a lack of invasion of the major portal vein (p=0.022), a lack of intrahepatic metastasis (p=0.010), lower the American Joint Committee on Cancer T stage (p=0.016), lower the Barcelona Clinic Liver Cancer stage (p=0.006), and lower α-fetoprotein levels (p=0.020). High AKR1B10 expression was also correlated with a lack of early recurrence (p=0.022). Multivariate analyses of survival revealed that intrahepatic metastases and lower albumin levels were independent predictors of both shorter recurrence-free survival and shorter disease-specific survival. High AKR1B10 expression was an independent predictor of both longer recurrence-free survival (p=0.024) and longer disease-specific survival (p=0.046).

Conclusions

High AKR1B10 protein expression might be useful as a marker of a favorable prognosis in patients with hepatocellular carcinoma after curative hepatectomy.     

Evidence for keratinocyte stem cells in vitro: Long term engraftment and persistence of transgene expression from retrovirus-transduced keratinocytes

Epidermis is renewed by a population of stem cells that have been defined in vivo by slow turnover, label retention, position in the epidermis, and enrichment in β₁ integrin, and in vitro by clonogenic growth, prolonged serial passage, and rapid adherence to extracellular matrix. The goal of this study is to determine whether clonogenic cells with long-term growth potential in vitro persist in vivo and give rise to a fully differentiated epidermis. Human keratinocytes were genetically labeled in culture by transduction with a retrovirus encoding the lacZ gene and grafted to athymic mice. Analysis of the cultures before grafting showed that 21.1–27.8% of clonogenic cells with the capacity for >30 generations were successfully transduced. In vivo, β-galactosidase (β-gal) positive cells participated in the formation of a fully differentiated epithelium and were detected throughout the 40-week postgraft period, initially as loosely scattered clusters and later as distinct vertical columns. Viable cells recovered from excised grafts were seeded at clonal densities and 23.3–33.3% of the colonies thus formed were β-gal positive. In addition, no evidence of transgene inactivation was obtained: all keratinocyte colonies recovered from grafted tissue that were β-gal negative also lacked the lacZ transgene. These results show that cells with long-term growth properties in vitro do indeed persist in vivo and form a fully differentiated epidermis, thereby exhibiting the properties of stem cells.     

The mechanism of thioredoxin reductase from human placenta is similar to the mechanisms of lipoamide dehydrogenase and glutathione reductase and is distinct from the mechanism of thioredoxin reductase from Escherichia coli

Thioredoxin reductase, lipoamide dehydrogenase, and glutathione reductase are members of the pyridine nucleotide–disulfide oxidoreductase family of dimeric flavoenzymes. The mechanisms and structures of lipoamide dehydrogenase and glutathione reductase are alike irrespective of the source (subunit M_r ≈55,000). Although the mechanism and structure of thioredoxin reductase from Escherichia coli are distinct (M_r ≈35,000), this enzyme must be placed in the same family because there are significant amino acid sequence similarities with the other two enzymes, the presence of a redox-active disulfide, and the substrate specificities. Thioredoxin reductase from higher eukaryotes on the other hand has a M_r of ≈55,000 [Luthman, M. & Holmgren, A. (1982) Biochemistry 21, 6628–6633; Gasdaska, P. Y., Gasdaska, J. R., Cochran, S. & Powis, G. (1995) FEBS Lett 373, 5–9; Gladyshev, V. N., Jeang, K. T. & Stadtman, T.C. (1996) Proc. Natl. Acad. Sci. USA 93, 6146–6151]. Thus, the evolution of this family is highly unusual. The mechanism of thioredoxin reductase from higher eukaryotes is not known. As reported here, thioredoxin reductase from human placenta reacts with only a single molecule of NADPH, which leads to a stable intermediate similar to that observed in titrations of lipoamide dehydrogenase or glutathione reductase. Titration of thioredoxin reductase from human placenta with dithionite takes place in two spectral phases: formation of a thiolate–flavin charge transfer complex followed by reduction of the flavin, just as with lipoamide dehydrogenase or glutathione reductase. The first phase requires more than one equivalent of dithionite. This suggests that the penultimate seleno-cysteine [Tamura, T. & Stadtman, T.C. (1996) Proc. Natl. Acad. Sci. USA 93, 1006–1011] is in redox communication with the active site disulfide/dithiol. Nitrosoureas of the carmustine type inhibit only the NADPH reduced form of human thioredoxin reductase. These compounds are widely used as cytostatic agents, so this enzyme should be studied as a target in cancer chemotherapy. In conclusion, three lines of evidence indicate that the mechanism of human thioredoxin reductase is like the mechanisms of lipoamide dehydrogenase and glutathione reductase and differs fundamentally from the mechanism of E. coli thioredoxin reductase.     

Impairment of afferent arteriolar myogenic responsiveness in the galactose-fed rat is prevented by tolrestat

Summary By permitting the separation of increased aldose reductase activity from hyperglycaemia and insulin deficiency, galactose-fed rats have constituted a useful model for investigating diabetic complications. Such rats manifest an impaired afferent arteriolar responsiveness to pressure similar to that of rats 4 to 6 weeks after induction of diabetes with streptozotocin. In the present study, we investigated whether treatment of galactose-fed rats with the aldose reductase inhibitor tolrestat prevents this autoregulatory defect and whether the blunted afferent arteriolar responsiveness to pressure is associated with impaired responsiveness to angiotensin II. Pressure-induced vasoconstriction of afferent arterioles was assessed in kidneys made hydronephrotic to allow direct visualization of renal microvessels by computer-assisted image processing. Vessel diameters were quantitated following stepwise increments of renal perfusion pressure (RAP; from 80 to 180 mm Hg) in kidneys of control rats and rats fed a diet for 2 weeks with 50% galactose with or without tolrestat. Subsequent to the pressure studies, angiotensin II (0.3 nmol/l) was added to the perfusate, and vessel diameters were reassessed. Control rats exhibited progressive afferent arteriolar vasoconstriction when RAP was increased from 80 to 180mm Hg (–17.2±1.0%; p<0.001). In contrast, myogenic responses to increases in pressure were absent in the arterioles of the galactose-fed rats (–4.1±1.9%; N.S.). Treatment with tolrestat completely prevented this impairment in afferent arteriolar responsiveness (–16.5±1.8%; p<0.001). The angiotensin II-induced vasoconstriction did not differ between control rats and galactose-fed rats. We conclude that increased aldose reductase activity contributes to impaired renal autoregulation in galactose-fed rats, a model of diabetic nephropathy, but is not involved in the loss of afferent arteriolar responsiveness to angiotensin II.Abbreviations STZ Streptozotocin - GFR Glomerular filtration rate - RAP renal artery pressure - AR aldose reductase Portions of this study were presented at 15th Scientific Meeting of the International Society of Hypertension, Melbourne, Australia, March 19–26, 1994     

Inhibitory Effects of Pepstatin A and Mefloquine on the Growth of Babesia Parasites

We evaluated the inhibitory effects of pepstatin A and mefloquine on the in vitro and in vivo growths of Babesia parasites. The in vitro growth of Babesia bovis, B. bigemina, B. caballi, and B. equi was significantly inhibited (P < 0.05) by micromolar concentrations of pepstatin A (50% inhibitory concentrations = 38.5, 36.5, 17.6, and 18.1 μM, respectively) and mefloquine (50% inhibitory concentrations = 59.7, 56.7, 20.7, and 4 μM, respectively). Furthermore, both reagents either alone at a concentration of 5 mg/kg or in combinations (2.5/2.5 and 5/5 mg/kg) for 10 days significantly inhibited the in vivo growth of B. microti in mice. Mefloquine treatment was highly effective and the combination treatments were less effective than other treatments. Therefore, mefloquine may antagonize the actions of pepstatin A against babesiosis and aspartic proteases may play an important role in the asexual growth cycle of Babesia parasites.     

Lagging strand replication of rolling-circle plasmids: Specific recognition of the ssoA-type origins in different gram-positive bacteria

Many bacterial plasmids replicate by a rolling-circle mechanism that involves the generation of single-stranded DNA (ssDNA) intermediates. Replication of the lagging strand of such plasmids initiates from their single strand origin (sso). Many different types of ssos have been identified. One group of ssos, termed ssoA, which have conserved sequence and structural features, function efficiently only in their natural hosts in vivo. To study the host specificity of sso sequences, we have analyzed the functions of two closely related ssoAs belonging to the staphylococcal plasmid pE194 and the streptococcal plasmid pLS1 in Staphylococcus aureus. The pLS1 ssoA functioned poorly in vivo in S. aureus as evidenced by accumulation of high levels of ssDNA but supported efficient replication in vitro in staphylococcal extracts. These results suggest that one or more host factors that are present in sufficient quantities in S. aureus cell-free extracts may be limiting in vivo. Mapping of the initiation points of lagging strand synthesis in vivo and in vitro showed that DNA synthesis initiates from specific sites within the pLS1 ssoA. These results demonstrate that specific initiation of replication can occur from the pLS1 ssoA in S. aureus although it plays a minimal role in lagging strand synthesis in vivo. Therefore, the poor functionality of the pLS1 in vivo in a nonnative host is caused by the low efficiency rather than a lack of specificity of the initiation process. We also have identified ssDNA promoters and mapped the primer RNAs synthesized by the S. aureus and Bacillus subtilis RNA polymerases from the pE194 and pLS1 ssoAs. The S. aureus RNA polymerase bound more efficiently to the native pE194 ssoA as compared with the pLS1 ssoA, suggesting that the strength of RNA polymerase–ssoA interaction may play a major role in the functionality of the ssoA sequences in Gram-positive bacteria.     

Depudecin induces morphological reversion of transformed fibroblasts via the inhibition of histone deacetylase

Depudecin is a fungal metabolite that reverts the rounded phenotype of NIH 3T3 fibroblasts transformed with v-ras and v-src oncogenes to the flattened phenotype of the nontransformed parental cells. The mechanism of detransformation induced by this agent had not been determined. Here, we demonstrate that depudecin inhibits histone deacetylase (HDAC) activity effectively both in vivo and in vitro. Depudecin induces similar morphological reversion in v-ras transformed NIH 3T3 cells as do other naturally occurring HDAC inhibitors such as trichostatin A or trapoxin. It competitively inhibits the binding of [³H]trapoxin in vitro and the nuclear binding of a trapoxin–coumarin fluorophore in vivo, suggesting that depudecin shares a nuclear binding protein and site on that protein with trapoxin. Furthermore, depudecin induces hyperacetylation of histones in a dose-dependent manner and at concentrations comparable with that required for detransformation. An in vitro histone deacetylase assay, using purified recombinant HDAC1, reveals that depudecin inhibits 50% of the enzyme activity at a concentration of 4.7 μM. These results demonstrate that depudecin is a novel HDAC inhibitor and suggest that its ability to induce morphological reversion of transformed cells is the result of its HDAC inhibitory activity.