PCR detection of human papillomavirus: comparison between MY09/MY11 and GP5+/GP6+ primer systems

Human papillomavirus (HPV) is an etiologic agent of cervical cancer and is the most common sexually transmitted disease in women. PCR amplification of HPV genomes is the most sensitive method for the detection of cervicovaginal HPV. We have compared the two most commonly used PCR primer sets, MY09/MY11 (MY-PCR) and GP5+/GP6+ (GP+-PCR), for the detection of HPV DNA in cervicovaginal lavage samples from 208 women. Oligonucleotide probes for 39 different HPV types were used. Both primer sets amplified a wide spectrum of HPV genotypes and detected similar overall prevalences of 45% (94 of 208) and 43% (89 of 208), respectively. The MY-PCR system detected 27 of 30 (90%) samples with multiple HPV types, whereas the GP+-PCR system detected 14 of 30 (47%) samples with multiple HPV types. Differences in the detection of HPV types 35, 53, and 61 were noted between the two primer systems. Serial dilution of plasmid templates indicated a 3-log decrease in the amplification of HPV type 35 by MY-PCR and HPV types 53 and 61 by GP+-PCR. These results indicate that although the MY-PCR and GP+-PCR identified nearly equivalent prevalences of HPV in a set of clinical samples, differences in the detection of specific types and infections with multiple types were found. Differences in the sensitivities and characteristics of the PCR systems for the detection of HPV within clinical samples should be considered when comparing data between studies and/or in designing new studies or clinical trials.

Kupffer cells contain a glycine-gated chloride channel

Here the effect of glycine on intracellular Ca2+ concentration ([Ca2+]i) in cultured Kupffer cells stimulated with lipopolysaccharide (LPS) was investigated to assess the possibility that they contain a glycine-gated chloride channel. LPS (10 micrograms/ml) increased [Ca2+]i rapidly, with peak values reaching 307 +/- 29 nM. Glycine (1 mM) prevented this increase nearly completely. Low concentrations of strychnine (1 microM), a glycine receptor antagonist, reversed the inhibitory effect of glycine completely; however, high concentrations of strychnine (1 mM) mimicked glycine. The effects of glycine and high-dose strychnine were prevented when cells were incubated in chloride-free buffer. Furthermore, potassium (25 mM) and LPS depolarized the Kupffer cell plasma membrane, whereas glycine caused hyperpolarization and prevented depolarization due to potassium and LPS. Moreover, tumor necrosis factor-alpha (TNF-alpha) production in cultured Kupffer cells due to LPS was decreased significantly by glycine. Therefore, it is concluded that Kupffer cells contain a glycine-gated chloride channel similar to that described previously in the central nervous system. Prevention of increases in [Ca2+]i due to LPS by activation of chloride influx reduced synthesis and release of toxic mediators by Kupffer cells.

Destruction of Kupffer cells increases survival and reduces graft injury after transplantation of fatty livers from ethanol-treated rats

This study investigated the role of Kupffer cells on survival and graft injury in transplanted fatty livers from rats treated acutely with ethanol. Donor rats were given ethanol (5 g/kg, by mouth) 20 hours before explantation, and liver grafts were preserved in University of Wisconsin cold storage solution for 24 to 42 hours prior to implantation. Blood samples were taken from the inferior vena cava for 3 hours after implantation. During this time, serum aspartate transaminase levels increased gradually from 122 U/L to 597 U/L in control rats, while ethanol treatment elevated values to 2,278 U/L. Gadolinium chloride (20 mg/kg, given intravenously to recipients 24 hours before explantation), a selective inactivator of Kupffer cells, minimized the increase in aspartate transaminase levels significantly. After implantation of grafts cold-stored for 42 hours, survival rates were 88% in control rats but only 33% in ethanol-treated rats. Gadolinium chloride improved survival nearly to control values. Ethanol nearly doubled white blood cell adhesion, an effect also largely blocked by gadolinium chloride. Further, alpha-(4-pyridyl 1-oxid)-N-tert-butylnitrone radical adducts detected in the bile were increased twofold by ethanol treatment. This effect was also reversed by gadolinium chloride. Taken together, these data indicate that survival is poorer and graft injury is greater in fatty livers from ethanol-treated rats. Inactivation of Kupffer cells minimized graft damage, most likely by improving hepatic microcirculation and diminishing lipid peroxidation.

Interleukin 2 production in vitro by peripheral lymphocytes in response to human papillomavirus-derived peptides: correlation with cervical pathology

Human papillomavirus (HPV) is believed to be the major cause of cervical cancer. To investigate whether a cellular immune response, especially a T helper type 1 response, is related to the natural defense against HPV-related cervical lesions, the interleukin 2 response of peripheral blood lymphocytes in vitro to overlapping peptides from HPV-16 E6 and E7 oncoproteins was compared with the degree of cervical cytological abnormality among 140 women in a cross-sectional study. We compared 66 women diagnosed with low-grade squamous intraepithelial lesions (LSIL), 21 with high-grade squamous intraepithelial lesions (HSIL), and 28 with invasive cervical cancer with 25 women who were cytologically normal but previously HPV-16 DNA positive. The fraction showing strong interleukin 2 production against HPV-16 peptides was greatest among cytologically normal women (35%) and declined with increasing disease severity [LSIL] (20%), HSIL, (17%), and cancer patients (7%); X2 test P for the trend = 0.02], whereas the responses against a recall influenza antigen were not significantly different among groups. Our finding suggests that a T helper lymphocyte type 1 response to HPV antigens is associated with disease status. This result may reflect a targeted effect of the disease on immune function or a protective effect of the immune response against disease progression.

Kupffer cell prostaglandin E2 stimulates parenchymal cell O2 consumption: alcohol and cell-cell communication

Several studies have demonstrated that ethanol can increase hepatic O2 uptake (e.g., produce a hypermetabolic state); however, a complete explanation of this important phenomenon remains unclear. Here, the effect of conditioned media from Kupffer cells isolated from rats chronically exposed to ethanol on O2 consumption of normal parenchymal cells was studied to evaluate the possibility that cell-cell communication participates in the mechanism of the hepatic hypermetabolic state. Kupffer cells were isolated from rats fed either a liquid control diet or a diet containing ethanol. Kupffer cells were cultured for 4 h, and conditioned media were incubated with parenchymal cells isolated from untreated rats in a closed chamber with an O2 electrode. O2 consumption of parenchymal cells incubated in fresh media or conditioned media from Kupffer cells from untreated rats was approximately 30 microliters.h-1. 10(6) cells-1; however, values were increased by > 30% by conditioned media from Kupffer cells isolated from rats treated with ethanol. Indomethacin, nisoldipine, and boiling the conditioned media blocked this stimulation, suggesting the involvement of eicosanoids. Indeed, prostaglandin E2 (PGE2) added directly to parenchymal cells increased O2 consumption in a dose-dependent manner by nearly 60%. Furthermore, PGE2 levels in conditioned media from Kupffer cells isolated from ethanol-treated rats were elevated about twofold. The addition of endotoxin to cultured cells caused a similar phenomenon. Taken together, these data support the hypothesis that Kupffer cells are activated by ethanol treatment to release mediators such a PGE2, which stimulate O2 consumption in parenchymal cells, possibly by mechanisms involving bacterial endotoxin.

Role of Kupffer cells in reperfusion injury in fat-loaded livers from ethanol-treated rats

Reperfusion injury was studied in blood-free perfused livers from fat-loaded, ethanol-treated rats. Rats were pair-fed a modified Lieber-DeCarli liquid diet containing 36% calories as ethanol or isocaloric maltose-dextrin for 4 to 5 weeks. Reperfusion injury to the liver, which occurs in previously hypoxic regions upon reintroduction of oxygen, was studied in a low-flow, reflow perfusion model. Lactate dehydrogenase in effluent perfusate increased from basal levels of < 1 to 17 IU/g/h in livers from controls, whereas prior alcohol treatment elevated values to 37 IU/g/h. Pretreatment of rats with gadolinium chloride (GdCl3, 20 mg/kg i.v.), a selective Kupffer cell toxicant, minimized lactate dehydrogenase release during reperfusion to 7 to 8 IU/g/h in livers from both groups. Rates of malondialdehyde production were 144 and 166 nmol/g/h during reperfusion in control and alcohol-treated rats, respectively, but values reached only 54 and 79 nmol/g/h after GdCl3 treatment. Interestingly, a typical PBN/carbon-centered free radical adduct signal was detected in bile of livers from ethanol-treated rats, but not in controls or ethanol-treated rats given GdCl3. Portal pressure increased during the reperfusion period in livers from alcohol-treated rats, although not in controls, and GdCl3 reduced it significantly. Taken together, these data indicate that reperfusion injury is greater in fatty livers from alcohol-treated rats in a blood-free model. Inactivation of Kupffer cells minimized reperfusion injury in both control and alcohol-treated rats, most likely by diminishing lipid peroxidation thereby improving hepatic microcirculation.

Food restriction stimulates conjugation of p-nitrophenol in perfused rat liver

Rates of conjugation of p-nitrophenol were studied in livers from normal and food-restricted rats perfused with either p-nitroanisole or p-nitrophenol. Female Sprague-Dawley rats had ad libitum access to a Purina 5001 nonpurified diet (control) or were given 65% of the intake of controls for 3 weeks. Livers were perfused with oxygenated Krebs-Henseleit buffer using a nonrecirculating system. Maximal rates of conjugation of p-nitrophenol, generated either from the O-demethylation of p-nitroanisole (200 microM) or from the infusion of p-nitrophenol (70 microM), were elevated significantly nearly twofold by food restriction. Thus, food restriction stimulates conjugation in the intact liver cell. Specifically, rates of conjugation were increased from 2.1 +/- 0.2 to 3.7 +/- 0.4 and from 3.3 +/- 0.6 to 5.8 +/- 0.5 mumol/g/h when 200 microM p-nitroanisole or 70 microM p-nitrophenol were infused, respectively. On the other hand, rates of conjugation were not affected by food restriction when low concentrations of p-nitroanisole (50 microM) or p-nitrophenol (20 microM) were infused. Further, food restriction did not alter rates of conjugation in isolated microsomes supplemented with excess UDPGA. Interestingly, both UDP-glucose and UDP-glucuronic acid were increased significantly in liver extracts from food-restricted rats when livers were perfused with high but not low concentrations of p-nitrophenol. Under these conditions, the increase in UDP-glucuronic acid was threefold. Moreover, food restriction increased carbohydrate release from the liver about twofold. Glycogen content was also increased significantly in liver extracts from 8.4 +/- 1.9 to 60.4 +/- 13.8 mmol/kg wet weight by food restriction. Taken together, these data support the hypothesis that food restriction stimulates conjugation of p-nitrophenol concentrations by increasing the supply of the pivotal cofactor UDP-glucuronic acid from carbohydrate reserves (e.g., glycogen).

Food restriction and stimulation of monooxygenation of p-nitroanisole in perfused rat liver

This study assessed the effect of food restriction on the metabolism of model monooxygenase substrates in the perfused rat liver. Female Sprague-Dawley rats has access ad lib. to a Purina 5001 nonpurified diet (control) or were given 65% of the intake of controls for 3 weeks. Livers were perfused with oxygenated Krebs-Henseleit buffer using a non-recirculating system, and the rates of monooxygenation of p-nitroanisole and 7-ethoxycoumarin were measured. The results indicate that food restriction stimulated p-nitroanisole O-demethylation from 2.9 +/- 0.2 to 4.6 +/- 0.5 mumol/(g.hr) when saturating concentrations of p-nitroanisole were infused. Concomitantly, the ratio of beta-hydroxybutyrate to acetoacetate (B/A) and the rates of ketogenesis (B + A) were increased significantly by food restriction. Further, p-nitroanisole (200 mumol/L) increased hepatic malate concentration nearly 3-fold in liver extracts from food-restricted rats. However, infusion of either a low concentration of p-nitroanisole (50 mumol/L) or 7-ethoxycoumarin (200 mumol/L) did not alter these parameters. On the other hand, food restriction did not alter rates of monooxygenation in isolated microsomes supplemented with excess NADPH. Taken together, these data support the hypothesis that high concentrations of p-nitroanisole increased monooxygenation in food-restricted rats by stimulating fatty acid oxidation, which elevates the mitochondrial NADH/NAD+ ratio. This, in turn, increases the availability of reducing equivalents in the form of NADPH by a malate-pyruvate exchange system, leading to increased drug metabolism.

Increase in oxygen uptake due to arachidonic acid is oxygen dependent in the perfused liver

The purpose of this study was to determine whether the effect of arachidonic acid on hepatic O2 uptake is O2 dependent and which region of the liver lobule it affects. In livers perfused at normal flow rates, infusion of arachidonate increased O2 uptake significantly by about 20-25 mumol.g-1.h-1. When the flow rate was doubled to make the hepatic O2 gradient shallower, the increase in O2 uptake due to arachidonate was two to three times larger (i.e., approximately 50 mumol.g-1.h-1). In livers perfused in the retrograde direction, maximal rates of O2 uptake were about twofold higher in upstream pericentral than in downstream periportal regions, and arachidonic acid nearly doubled O2 uptake in downstream areas without affecting rates in upstream regions. Thus it is concluded that arachidonate stimulates O2 uptake in an O2-dependent manner. This effect was sensitive to an inhibitor of the lipoxygenase, nordihydroguaiaretic acid, in perfused liver but not in isolated hepatocytes. In addition, conditioned medium from Kupffer cells incubated at high O2 tension stimulated parenchymal cell O2 uptake. Furthermore, arachidonate increased intracellular Ca2+ in isolated Kupffer cells in a dose-dependent manner. These findings suggest that eicosanoids produced by nonparenchymal cells participate in a hepatic O2 sensor mechanism involving Ca2+ that regulates O2 uptake by parenchymal cells in the liver.

Stimulation of monooxygenation and conjugation after liver transplantation in the rat: involvement of Kupffer cells

The success rate of liver transplantation has improved markedly during the last few years and, although this patient population receives multiple drug therapies, the effect of liver transplantation on drug metabolism has been studied very little. Therefore, the purpose of this study was to assess the metabolism of model drug substrates after liver transplantation in the rat. Rat livers were stored for 4 hr in cold Euro-Collins solution, transplanted orthotopically, and then perfused 2 hr later with oxygenated Krebs-Henseleit buffer, using a nonrecirculating system. Rates of monooxygenation of the model compound p-nitroanisole, conjugation of p-nitrophenol, and uptake of oxygen were measured. All parameters studied were elevated significantly, by nearly 2-fold, by transplantation. Specifically, monooxygenation was increased from 2.9 +/- 0.2 to 5.1 +/- 0.4 mumol/g/hr, conjugation was elevated from 3.3 +/- 0.6 to 7.7 +/- 0.1 mumol/g/hr, and O2 uptake was stimulated from basal values of 114 to 197 mumol/g/hr. Transplantation did not, however, alter rates of monooxygenation and conjugation in isolated microsomes supplemented with excess cofactor. When donor rats were pretreated with the Kupffer cell toxicant gadolinium chloride (10 mg/kg, intravenously) 30 hr before liver storage, the elevation after transplantation in all parameters studied was prevented. Depletion of carbohydrate reserves by fasting of donor rats did not prevent stimulation of monooxygenation and conjugation. On the other hand, urea synthesis from ammonium chloride, a process dependent on mitochondrial NADPH, was increased and monooxygenation was diminished after transplantation, suggesting the involvement of mitochondria in this phenomenon. Indeed, mitochondria isolated 2 hr postoperatively exhibited significantly elevated respiratory control ratios and higher state 3 rates of respiration. Taken together, these data support the hypothesis that Kupffer cells, activated by transplantation, release mediators that stimulate mitochondria in parenchymal cells and enhance drug metabolism by increasing cofactor supply (e.g., NADPH for monooxygenation and UDP-glucuronic acid for glucuronidation).

Food restriction increases detoxification of polycyclic aromatic hydrocarbons in the rat

It is well known that food restriction diminishes tumor formation, but mechanisms responsible are difficult to define because multiple physiological changes result from dietary alterations. Studies in this report were designed to focus specifically on the effects of food restriction on hepatic metabolism of polycyclic aromatic hydrocarbons following liver transplantation. By placing livers from food-restricted and untreated rats into naive controls, the effects of diet could be restricted to the liver. After a 15 min infusion of [3H]benzo[a]pyrene under these conditions, food restriction increased polar metabolites in liver (70 pmol/g) and blood (8 pmol/ml) compared to controls approximately 2-fold. Four hours after liver transplantation, levels of polar metabolites in blood were diminished by approximately 50% but were still approximately 2-fold higher in the food-restricted than in the control group. Lung, kidney, spleen, adrenal, ovary, colon, heart and brain also contained higher levels of polar metabolites in the food-restricted than in the control group. The more hydrophobic glucuronides and sulfate conjugates accounted for most of the elevation in polar metabolites in blood from the food-restricted group. In spite of the increase in circulating metabolites in blood of food-restricted animals, DNA binding in liver, lung and kidney was identical in tissues from control and food-restricted groups. In order to evaluate the hypothesis that food restriction stimulated the release of hepatic benzo[a]pyrene metabolites, a liver perfusion model was employed. Maximal rates of release of polar metabolites into the effluent perfusate were approximately 30 and approximately 45 nmol/g/h in livers of control and food-restricted rats respectively. Moreover, rates of metabolism of the model compound p-nitroanisole and glucuronidation of p-nitrophenol were also approximately 2-fold higher in livers from food-restricted than control rats. However, rates of monooxygenation were the same in microsomes prepared from livers of food-restricted or control animals. These results support the hypothesis that food restriction enhances the supply of cofactors which stimulate metabolism of polycyclic aromatic hydrocarbons. This detoxification process may be an important mechanism involved in the protective action of reduced food intake.

Unique role of oxygen in regulation of hepatic monooxygenation and glucuronidation

The purpose of this study was to evaluate the hypothesis that NADPH supply in intact cells is regulated by oxygen tension. This was accomplished by studying monooxygenation in perfused livers from Ah locus-responsive C57BL/6J mice, where rates of monooxygenation are high. Elevation of flow rate decreases the hepatic O2 gradient and increases O2 delivery to the organ. Under these conditions, rates of p-nitroanisole O-demethylation were 2-3 times higher in perfused livers from fed or fasted mice at high (10 ml/min) compared with normal (5 ml/min) flow rates. Rates of monooxygenation were directly proportional to oxygen tension (half-maximal rates occurred with approximately 400 microM O2). On the other hand, rates were independent of oxygen concentration in isolated microsomes where NADPH was supplied in excess. The decrease in rate due to diminished O2 concentration in the intact organ could not be attributed to hypoxia, because O2 tension in the effluent perfusate exceeded 50 microM even when influent perfusate was saturated with 25% O2 and ATP/ADP ratios were in the normal range. Thus, monooxygenation of p-nitroanisole in perfused mouse liver is dependent on oxygen tension. Similarly, glucuronidation of p-nitrophenol was oxygen dependent in the intact organ but not in isolated microsomes supplemented with UDP-glucuronic acid. Taken together, these data support the hypothesis that, at high oxygen tensions (e.g., in periportal regions of the liver lobule), mitochondrial activity is increased, which in turn enhances NADPH and UDP-glucuronic acid turnover, leading to accelerated rates of monooxygenation and glucuronidation in intact cells. In support of this idea, NH4Cl, which utilizes NADPH for urea synthesis, inhibited monooxygenation in the perfused mouse liver at high but not low flow rates. Thus, important phase I and II detoxification reactions are regulated indirectly by the hepatic oxygen gradient, via mechanisms involving cofactor supply, when cytochrome P-450 is not limiting.