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Biomedical subjects

H L Bonkovsky

Publications and source records attributed to H L Bonkovsky.

At least 19 recordsLinked to original sources
PubMed2001

Increased heme oxygenase activity in splanchnic organs from portal hypertensive rats: role in modulating mesenteric vascular reactivity.

BACKGROUND/AIMS: We have recently demonstrated that heme oxygenase-1 is upregulated in splanchnic organs of portal hypertensive rats. In the present study, we assessed whether heme oxygenase enzymatic activity is increased in splanchnic organs of portal hypertensive rats, and the relative contribution of heme oxygenase and nitric oxide synthase to the vascular hyporeactivity in portal hypertension. METHODS: Heme oxygenase activity was measured in splanchnic organs of portal hypertensive and sham-operated rats. The effects of heme oxygenase and nitric oxide synthase inhibition on pressure responses to potassium chloride and methoxamine were assessed in perfused mesenteric vascular beds of portal hypertensive and sham-operated rats. RESULTS: Heme oxygenase activity was increased in the mesentery, intestine, liver, and spleen of portal hypertensive rats. The hyporeactivity to potassium chloride in portal hypertensive rats was overcome after simultaneous inhibition of both heme oxygenase and nitric oxide synthase, but only partially attenuated after nitric oxide synthase inhibition alone. The hyporeactivity to methoxamine was completely reversed after nitric oxide synthase blockade. CONCLUSIONS: These results demonstrate that heme oxygenase activity is increased in splanchnic organs of portal hypertensive rats. They also suggest that heme oxygenase contributes to the hyporeactivity to potassium chloride, but not to methoxamine, in portal hypertensive rats.

Animals↗
PubMed2001

Extrahepatic manifestations of infection with hepatitis C virus.

Chronic hepatitis C is associated with, and may trigger or exacerbate, an extraordinary variety of extrahepatic manifestations. Most of these manifestations affect the skin, the most frequent and important of which are the leukocytoclastic vasculitis of MC type II and PCT. The former is an example of an autoimmune disorder triggered by HCV infection, whereas PCT is a skin disease caused by hepatic overproduction of uro- and 7-carboxyl porphyrins caused by increased oxidative stress in hepatocytes. Currently available effective therapies of CHC (IFN, ribavirin) may also trigger or exacerbate extrahepatic manifestations, especially including autoimmune thyroiditis, skin rashes, and hemolytic anemia.

Arthralgia↗
PubMed2001

Comparative effects of different doses of ribavirin plus interferon-alpha2b for therapy of chronic hepatitis C: results of a controlled, randomized trial.

Compared to either drug alone, therapy with the combination of ribavirin and interferon-alpha leads to improved rates of response in patients with chronic hepatitis C. Side effects often mandate downward dose adjustment or cessation of therapy, and the optimal dose of ribavirin has not been established. The aim of this study was to learn whether 600 mg ribavirin per day would prove as efficacious as 1,000-1,200 mg/day when combined with interferon (3 million units thrice weekly) for therapy of patients previously treated with standard interferon who had failed to respond or who had relapsed. We enrolled 69 patients with chronic hepatitis C and compensated liver disease: 45 were men, 65 were Caucasian, 48 were infected with genotype 1 hepatitis C virus. By random assignment, 35 received 600 mg ribavirin/day (group A), whereas the other 34 received 1,000 mg (< or = 75 kg body wt) or 1,200 mg/day (>75 kg body wt) (group B). At baseline, the two groups were well matched for demographic and laboratory features. In both groups, mean serum levels of alanine aminotransferase (ALT) and hepatitis C viral (HCV) RNA levels fell promptly and remained significantly lower than baseline throughout 24 weeks of therapy. There was no significant difference in mean levels of ALT or HCV RNA during therapy or at the end of follow-up (24 weeks after cessation of therapy). At the end of 24 weeks of posttherapy follow-up, 12 patients in each group had undetectable HCV RNA in serum, whereas 11 (31%) in group A and 9 (26.5%) in group B had normal serum ALT levels. The lower doses of ribavirin (group A) were tolerated better. In conclusion, in previous nonresponders or relapsers to interferon done, combination therapy with interferon-alpha2b (3 MU thrice weekly) + 600 mg ribavirin/day is tolerated better and is as effective as interferon plus higher (standard) doses of ribavirin (1,000-1,200 mg/day).

Adult↗
PubMed2001

Hepatitis C: a review and update.

UNLABELLED: The hepatitis C virus is an RNA virus that is a major cause of acute and chronic hepatitis. It is contracted chiefly through parenteral exposure to infected material such as blood transfusions or injections with dirty needles. Those at highest risk for development of hepatitis C are injection-drug users, people who snort cocaine with shared straws, and health care workers who are at risk for needle-stick and other exposures. Although the incidence of acute hepatitis C infection has fallen dramatically in the United States during the past decade, the prevalence of infection remains high (approximately 2.7 million Americans) because chronic hepatitis C develops in about 75% of those infected. Both acute and chronic hepatitis C are asymptomatic in most patients. However, chronic hepatitis C is a slowly progressive disease and results in severe morbidity in 20% to 30% of infected persons. Chronic hepatitis C is associated with a host of extrahepatic manifestations, many of which may be seen by dermatologists. The most frequent of these are mixed cryoglobulinemia with leukocytoclastic vasculitis and porphyria cutanea tarda. (J Am Acad Dermatol 2001;44:159-79.) LEARNING OBJECTIVE: At the conclusion of this learning activity, participants should be familiar with the essentials of the virology of the hepatitis C virus and the major features of the human diseases caused by hepatitis C viral infection; the extrahepatic manifestations of hepatitis C viral infection, with particular emphasis upon dermatologic manifestations, including leukocytoclastic vasculitis, porphyria cutanea tarda, and lichen planus; and the current methods of management of hepatitis C and its extrahepatic manifestations.

Autoimmune Diseases↗
PubMed2001

Urea and hypertonicity increase expression of heme oxygenase-1 in murine renal medullary cells.

Epithelial cells derived from the mammalian kidney medulla are responsive to urea at the levels of signal transduction and gene regulation. Hybridization of RNA harvested from control- and urea-treated murine inner medullary collecting duct (mIMCD3) cells with a cDNA expression array encoding stress-responsive genes suggested that heme oxygenase (HO)-1 mRNA was upregulated by urea. RNase protection assay confirmed this upregulation; hypertonicity also increased HO-1 mRNA expression but neither hypertonic NaCl nor urea were effective in the nonrenal 3T3 cell line. The effect on HO-1 expression appeared to be transcriptionally mediated on the basis of mRNA half-life studies and reporter gene analyses using the promoters of both human and chicken HO-1. Although urea signaling resembles that of heavy metal signaling in other contexts, the effect of urea on HO-1 transcription was independent of the cadmium response element in this promoter. Urea-inducible HO-1 expression was sensitive to antioxidants but not to scavengers of nitric oxide. Urea also upregulated HO-1 protein expression and pharmacological inhibition of HO-1 action with zinc protoporphyrin-sensitized mIMCD3 cells to the adverse effects of hypertonicity but not to urea. Coupled with the prior observation of others that HO-1 expression increases along the renal corticomedullary gradient, these data suggest that HO-1 expression may comprise an element of the adaptive response to hypertonicity and/or urea in renal epithelial cells.

3T3 Cells↗
PubMed2001

Induction of heme oxygenase-1 by phenylarsine oxide. Studies in cultured primary liver cells.

Heme oxygenase-1, the major inducible isoform of heme oxygenase (HO), can be induced by heme and numerous other physical and chemical factors, many of which cause cellular 'stress'. This has led to the realization that HO-1 is a major highly conserved stress or heat shock protein. Recent work has implicated activation of mitogen-activated protein kinases and other kinases in the mechanism of induction of HO-1, and suggested that signal transduction pathways through tyrosine kinases are involved in induction of HO-1 gene expression by stress inducers. We hypothesized that phenylarsine oxide (PAO), an inhibitor of protein tyrosine phosphatases (PTPs), might up-regulate the HO-1 gene. Here, we show that a remarkably brief (1-15 min) exposure of normal hepatocytes to low concentrations (0.5-3 microM) of PAO produces a marked increase in mRNA and protein of HO-1. This increase is comparable to the level obtained by addition of heme (20 microM), and occurs without producing changes in cellular glutathione levels or stabilization of HO-1 message. Preincubation of cells with inhibitors of protein synthesis decreased the ability of PAO to increase levels of HO-1 mRNA, suggesting that the inductive effect requires de novo protein synthesis. Addition of thiol donors abrogated the PAO-mediated induction of HO-1 in a dose dependent fashion. Addition of genistein, a tyrosine kinase inhibitor, blunted the induction produced by both PAO and heme. After brief incubations with PAO or heme, cell extracts showed comparable increases in levels of protein tyrosine phosphorylation in general, and specifically in ZAP70 kinase. Our results are consistent with the proposition that induction of HO-1 by PAO involves inhibition of specific PTP(s), and that the mechanisms of induction of HO-1 by PAO and by heme may share some common pathways.

Actins↗
PubMed2000

Induction of the heme oxygenase-1 gene by metalloporphyrins.

Induction of expression of heme oxygenase-1 (HO-1) has been studied in primary cultures of chick embryo liver cells and in the LMH line of avian hepatoma cells. Cells were transiently transfected with selected constructs containing portions of the 5'-untranslated (promoter) region of the HO-1 gene linked to luciferase as reporter gene. LMH cells that had been stably transfected with selected wild type or mutant constructs were also studied. Metalloporphyrins, especially Fe protoporphyrin (heme) and Co protoporphyrin strongly induced luciferase expression in both types of transfected cells. Low concentrations of Zn mesoporphyrin, an inhibitor of HO activity, exerted a synergistic effect on heme-, but not Co protoporphyrin-dependent induction. The antioxidant and &bond;SH donor N-acetyl cysteine had little effect on the metalloporphyrin-dependent inductions of HO-1, in contrast to its marked inhibitory effect on the sodium arsenite-dependent induction of the HO-1 gene. Deletional analysis showed that the key element(s) required for the metalloporphyrin-dependent induction of HO-1 is located between -3.6 and -5.6 kb upstream of the transcription starting point. Data from electrophoretic mobility shift and site-directed mutagenesis experiments excluded a role for consensus AP-1 binding elements at -1576, -3647, or -4578 in the inductions produced by heme or Co protoporphyrin.

Animals↗
PubMed2000

Iron reduction before and during interferon therapy of chronic hepatitis C: results of a multicenter, randomized, controlled trial.

Patients with chronic hepatitis C and low serum and hepatic iron stores may have an improved response to interferon (IFN). We tested whether iron reduction before and during IFN therapy would lead to an improved sustained biochemical and virological response compared with IFN alone. Eighty-two previously untreated patients with chronic hepatitis C were randomized to either: group A IFN-alpha2b 3 MU 3 times per week for 6 months, or group B iron reduction before and during IFN-alpha2b 3 MU 3 times per week for 6 months. Group B patients had lower mean serum alanine transaminase (ALT) levels than group A patients during treatment and follow-up. Group B patients had significantly lower mean hepatitis C virus (HCV)-RNA levels at treatment weeks 4 and 12 (P <.05). Serum HCV RNA was undetectable at the end of treatment in 15 group B patients compared with 7 group A patients (P =.03); 7 group B patients and 3 group A patients had persistently undetectable serum HCV RNA 24 weeks after the end of therapy (P =.20). Paired pre- and posttreatment liver biopsies in 18 group B patients demonstrated significant improvements in 2 of the 3 inflammation scores of the Knodell histological activity index (P <. 05). No changes occurred in the paired biopsies from 15 group A patients. We conclude that iron reduction via therapeutic phlebotomy improves the end-of-treatment virological and histological response to short-term IFN therapy. Additional studies are needed to determine if iron reduction in combination with higher doses or longer duration of IFN may be of benefit.

Adult↗
PubMed2000

Iron-induced liver injury.

Iron, either in the form of heme or non-heme compounds, is essential to life, but it can also pose serious health risks. The liver is a principal target for iron toxicity because it is chiefly responsible for taking up and storing excessive amounts of iron. The major hepatic toxicities of iron overload include damage to multiple cell types (hepatocytes, Kupffer cells, hepatic stellate cells) and to multiple subcellular organelles (mitochondria, lysosomes, and smooth endoplasmic reticulum). Heavy iron overload, as occurs in primary (hereditary) or secondary forms of hemochromatosis, may cause cirrhosis, liver failure, and hepatocellular carcinoma. In addition, iron has been shown to be a contributory factor in the development or progression of alcoholic liver disease, nonalcoholic liver steatohepatitis, chronic viral hepatitis, prophyria cutanea tarda, and, perhaps, in alpha 1-antitrypsin deficiency and end-stage liver disease, regardless of cause.

Fat Necrosis↗
PubMed2000

Upstream regulatory elements in chick heme oxygenase-1 promoter: a study in primary cultures of chick embryo liver cells.

Previously, chick heme oxygenase-1 (cHO-1) gene was cloned by us and two regions important for induction by sodium arsenite were identified. These two regions were found to contain consensus sequences of an AP-1 (-1580 to -1573) and a MRE/cMyc complex (-52 to -41). In the current study, the roles of these two elements in mediating the sodium arsenite or cobalt chloride dependent induction of cHO-1 were investigated further. DNA binding studies and site-directed mutagenesis studies indicated that both the AP-1 and MRE/cMyc elements are important for the sodium arsenite induction, while cobalt chloride induction involves only the AP-1 element. Electrophoretic mobility shift assays showed that nuclear protein binding to the AP-1 element was increased by both sodium arsenite or cobalt chloride treatment, whereas the binding of proteins to the MRE/cMyc element showed a high basal expression in untreated cells and the binding activity was only slightly increased by sodium arsenite treatment. Site-directed mutagenesis studies showed that, to completely abolish sodium arsenite induction, both the AP-1 and MRE/cMyc elements must be mutated; mutation of either element alone resulted in only a partial effect. In contrast, a single mutation at AP-1 element was sufficient to reduce the cobalt chloride induction almost completely. The MRE/cMyc complex plays a major role in the basal level expression, and shares some similarities to the upstream stimulatory factor element (USF) identified in the promoter regions of mammalian HO-1 genes and other stress regulated genes. Because sodium arsenite is known to cause oxidative stress and because activation of AP-1 proteins has been shown to be a key step in the oxidative stress response pathway, we also explored the possibility that the induction of the cHO-1 gene by sodium arsenite is mediated through oxidative stress pathway(s) by activation of AP-1 proteins. We found that pretreatment with antioxidants (N-acetyl cysteine or quercetin) reduced the induction of the endogenous cHO-1 message or cHO-1 reporter construct activities induced by sodium arsenite or cobalt chloride. These antioxidants also reduced the protein binding activities to the AP-1 element in the electrophoretic mobility shift assays. In summary, induction of the cHO-1 gene by sodium arsenite or cobalt chloride is mediated by activation of the AP-1 element located at -1,573 to -1,580 of the 5'UTR.

Animals↗
PubMed2000

Iron reduction as an adjuvant to interferon therapy in patients with chronic hepatitis C who have previously not responded to interferon: a multicenter, prospective, randomized, controlled trial.

Hepatic iron concentration has consistently been observed as being directly correlated with the response to interferon therapy in chronic hepatitis C virus (HCV). We therefore conducted a randomized, controlled trial comparing iron reduction by phlebotomy with iron reduction followed by retreatment with interferon in 96 patients with chronic hepatitis C who had previously not responded to a course of interferon. During the initial phase when all patients were undergoing phlebotomy, we found that serum alanine transaminase (ALT) activities decreased but by less than 50% from baseline in 67 patients (89%), decreased by more than 50% in 12 patients (13%) and became normal in 9 patients (9%) with no overall change in HCV-RNA levels. Subsequently no patient in either treatment group achieved a sustained virologic response. Improvements in necroinflammatory changes were noted in liver biopsy specimens in those patients receiving phlebotomy plus interferon (mean index 8.59 vs. 7.37, P <. 05). A slight but not statistically significant decrease in histologic activity index was noted in those subjects treated by phlebotomy alone (mean index 8.4 vs. 7.75, P not significant). We conclude that, although prior phlebotomy therapy does not improve the rate of sustained response to interferon retreatment, it does result in less liver injury manifested by a decrease in serum transaminase activity and a slight improvement in liver histopathology.

Adult↗
PubMed2000

Hepatotoxicity due to troglitazone: report of two cases and review of adverse events reported to the United States Food and Drug Administration.

Two patients (a 48-year-old woman and a 62-year-old man) developed clinical and laboratory signs of hepatotoxicity due to troglitazone (Rezulin), a thiazolidinedione used in treatment of diabetes mellitus. There was no clear clinical evidence of drug allergy, although the woman experienced colitis before the onset of recognized hepatotoxicity. Liver biopsies showed bridging necrosis and fibrosis in the woman and hepatitis with granuloma formation in the man. The abnormalities in liver chemistries resolved promptly upon cessation of the drug. Cases involving 46 patients reported to the United States Food and Drug Administration are also reviewed. Troglitazone is a useful new oral antihyperglycemic agent, but in about 1.9% of patients hepatotoxicity has occurred, which may be severe and even fatal. Frequent monitoring of serum liver chemistries in patients taking the drug is essential.

Chromans↗
PubMed2000

Management of recurrent hepatitis C after liver transplantation: a concise review.

Recurrent hepatitis C infection and subsequent graft failure are increasingly recognized problems after orthotopic liver transplantation. Although many prospective therapeutic, controlled trials in primary hepatitis C disease have been reported, large-scale studies are yet to be performed in patients with posttransplant recurrent hepatitis C after liver transplantation. In this review, we summarize the current literature on the therapeutic approaches for recurrent hepatitis C and discuss the results of published studies on therapy with ribavirin or interferon (IFN) alone and on combination therapy with IFN plus ribavirin. Further, we discuss results of prophylactic approaches to the problem of recurrent hepatitis C after transplant. Finally, we discuss additional aspects of anti-hepatitis C virus therapy after liver transplantation.

Antiviral Agents↗
PubMed2000

Ubiquitin as a marker of cell injury in nonalcoholic steatohepatitis.

Ubiquitin (UB), an intracellular protein that binds to other proteins to target them for proteolysis, is associated with Mallory hyalin (MH), which supports a biopsy diagnosis of nonalcoholic steatohepatitis (NASH). We analyzed 54 liver biopsy specimens from 49 patients with a clinical diagnosis of NASH for immunoreactive UB and multiple features of necroinflammation, fibrosis, and Prussian blue-positive iron to determine whether the presence of immunoreactive UB increases detection of MH or correlates with other features of cell injury or mutations of the HFE gene. MH and UB were graded. Analysis for HFE gene mutations was performed in 48 patients. Biopsy diagnoses were distributed as follows: NASH, 42; steatosis, 10; and nonspecific changes, 2. UB was present in 20 specimens and MH in 23. Of 31 specimens with 0 MH, 6 had UB; of 14 with 1 + (questionable) MH, 7 had 1+ or 2+ UB. UB correlated positively and significantly with the diagnosis and grade of NASH, presence of MH, cell swelling, lobular inflammation, and fibrosis. Immunostaining for UB may enhance detection of MH in questionable cases, support the diagnosis of NASH, and indicate which patients may be at risk for progression of disease.

Adult↗
PubMed1999

Effects of phenylarsine oxide on expression of heme oxygenase-1 reporter constructs in transiently transfected cultures of chick embryo liver cells.

Heme oxygenase catalyzes the first and rate-controlling step of heme catabolism. Induction of heme oxygenase-1 can be caused by numerous factors, including heme, other metalloporphyrins, transition metal ions, heat shock, ultraviolet light, phorbol esters, sodium arsenite, and phenylarsine oxide (PAO). Induction of this enzyme may protect cells from oxidative damage. Using heme oxygenase-1 promoter/reporter gene constructs, we have previously reported that the sodium arsenite-mediated induction of heme oxygenase-1 in chick embryo liver cells and chicken hepatoma (LMH) cells involves an AP-1 element. We have now investigated whether the PAO-mediated induction of heme oxygenase-1 also involves an AP-1 element. Primary cultures of chick embryo liver cells were transiently transfected with heme oxygenase-1 promoter/reporter gene constructs, treated with PAO, and reporter gene activities were measured. We found that the PAO-mediated increase in reporter gene activity was dose- and time-dependent. This activity was decreased by prior treatment with N-acetylcysteine. Studies with mutated constructs showed that both an AP-1 element and a metal responsive element are involved in the PAO-mediated induction of the heme oxygenase-1 reporter construct. Electrophoretic mobility shift assays showed that nuclear proteins from PAO-treated cells had increased binding to an AP-1 probe, and that this increase was abrogated by N-acetylcysteine. These findings support the hypothesis that the PAO-mediated induction of heme oxygenase-1 is caused by activation of AP-1 and MRE/cMyc elements and may involve nuclear proteins whose states of phosphorylation determine binding to regulatory elements, and thus the level of expression of heme oxygenase-1.

Acetylcysteine↗
PubMed1999

Heme biosynthesis in a chicken hepatoma cell line (LMH): comparison with primary chick embryo liver cells (CELC).

5-Aminolevulinic acid synthase (ALA synthase), the rate-controlling enzyme of hepatic heme biosynthesis, is feed-back repressed by heme. In the liver, chemicals such as barbiturates markedly induce ALA synthase, especially in the presence of partial defects of heme biosynthesis. The inducibility and regulation of ALA synthase have been investigated using a variety of models, including intact animals and liver cell culture systems. A widely used model that closely approximates what occurs in vivo and in humans is that of primary cultures of chick embryo liver cells (CELCs). However, CELCs have some limitations: the cells obtained are somewhat heterogeneous; isolation and culture must be repeated every week resulting in weekly variations; and cells are short-lived limiting the feasibility of time-course and transfection studies. The aim of this study was to determine if LMH cells, a chick hepatoma cell line, are a good model comparable to that of CELCs. In both cells similar patterns of response of, ALA synthase activities and mRNA levels, and of porphyrin accumulation were obtained following treatments known to affect heme biosynthesis. Similarly, heme repressed ALA synthase mRNA levels in both cell types and ALA synthase activities in LMH cells. We conclude that LMH cells are a useful model for the study of hepatic heme biosynthesis and regulation of ALA synthase.

5-Aminolevulinate Synthetase↗
PubMed1999

Effects of selected antihypertensives and analgesics on hepatic porphyrin accumulation: implications for clinical porphyria.

When patients with acute porphyrias are treated with antihypertensives and analgesics, they could be placed at increased risk of developing porphyric attacks, since little is known about the potential for many of these drugs to induce these attacks. We used primary chick embryo liver cells, which maintain intact heme synthesis and regulation, to study the effects of antihypertensives and analgesics on porphyrin accumulation. Cells were treated with desferrioxamine to block heme synthesis partially, simulating conditions encountered in porphyric patients. Typically, cells were treated for 20 hr with the test drugs (3.16 to 1000 microM), along with desferrioxamine. Porphyrins were measured spectrofluorometrically, as uro-, copro,- and protoporphyrin. The evaluated drugs included six antihypertensives (two calcium channel blockers, an angiotensin receptor antagonist, and three inhibitors of angiotensin converting enzyme) and eight analgesics. Of the calcium channel blockers tested, nifedipine greatly increased porphyrin accumulation, whereas diltiazem caused only a slight increase. Losartan (an angiotensin receptor antagonist), captopril, or lisinopril (two angiotensin converting enzyme inhibitors) produced only small increases in porphyrin accumulation. In contrast, enalapril (another angiotensin converting enzyme inhibitor) substantially increased porphyrin accumulation when given in high concentrations. Among the analgesics tested, fentanyl and tramadol produced the highest porphyrin accumulations. Nalbuphine, hydrocodone, oxycodone, and dezocine were moderately or weakly porphyrogenic, whereas buprenorphine and morphine did not increase porphyrin accumulation. These studies suggest that patients with acute porphyrias may be at greater risk for developing porphyric attacks when treated with nifedipine (compared with diltiazem), enalapril (compared with captopril or lisinopril), and tramadol (compared with the other analgesics).

Analgesics↗