Role of the proteasome in ethanol-induced liver pathology

The ubiquitin-proteasome system has come to be known as a vital constituent of mammalian cells. The proteasome is a large nonlysosomal enzyme that acts in concert with an 8.5 kDa polypeptide called ubiquitin and a series of conjugating enzymes, known as E1, E2 and E3, that covalently bind multiple ubiquitin moieties in a polyubiquitin chain to protein substrates in a process called ubiquitylation. The latter process targets protein substrates for unfolding and degradation by the 26S proteasome. This enzyme system specifically recognizes and degrades polyubiquitylated proteins, many of which are key proteins involved in cell cycle regulation, apoptosis, signal transduction, and antigen presentation. The 26S proteasome contains a cylinder-shaped 20S catalytic core that, itself, degrades proteins in an ATP- and ubiquitin-independent manner. The 20S form is actually the predominant enzyme form in mammalian cells. Proteolysis by the constitutive 20S proteasome is vital in removing oxidized, misfolded and otherwise modified proteins. Such degradation is critical as a means of cellular detoxification, as intracellular accumulation of damaged and misfolded proteins is potentially lethal. Studies have shown that inhibition of proteasome activity can lead to cell death. Ethanol and its metabolism cause partial inhibition of the proteasome. This leads to a number of pleiotropic effects that can affect a variety of cellular processes. This critical review describes important aspects of ethanol metabolism and its influence on the proteasome. The review will summarize recent findings on: (1) the interactions between the proteasome and the ethanol metabolizing enzyme, CYP2E1; (2) the dynamics of proteasome inhibition by ethanol in animal models and cultured cells; (3) ethanol-elicited suppression of proteasome activity and its effect on signal transduction; (4) The role of proteasome inhibition in cytokine production by liver cells; and (5) ethanol elicited suppression of peptide hydrolysis and the potential effects on antigen presentation. While the principal focus is on alcohol-induced liver injury, the authors foresee that the findings presented in this review will prompt further research on the role of this proteolytic system in other tissues injured by excessive alcohol consumption.

L-Buthionine (S,R) sulfoximine depletes hepatic glutathione but protects against ethanol-induced liver injury

BACKGROUND

L-Buthionine (S,R) sulfoximine (BSO) is an inhibitor of glutathione biosynthesis and has been used as an effective means of depleting glutathione from cells and tissues. Here we investigated whether treatment with BSO enhanced ethanol-induced liver injury in mice.

METHODS

Female C57Bl/6 mice were pair fed with control and ethanol-containing liquid diets in which ethanol was 29.2% of total calories. During the final 7 days of pair feeding, groups of control-fed and ethanol-fed mice were given 0, 5 or 7.6 mM BSO in the liquid diets.

RESULTS

Compared with controls, ethanol given alone decreased total liver glutathione. This effect was exacerbated in mice given ethanol with 7.6 mM BSO, causing a 72% decline in hepatic glutathione. While ethanol alone caused no decrease in mitochondrial glutathione, inclusion of 7.6 mM BSO caused a 2-fold decline compared with untreated controls. L-Buthionine (S,R) sulfoximine did not affect ethanol consumption, but serum ethanol levels in BSO-treated mice were nearly 6-fold lower than in mice given ethanol alone. The latter decline in serum ethanol was associated with a significant elevation in the specific activities of cytochrome P450 2E1 and alcohol dehydrogenase in livers of BSO-treated animals. Ethanol consumption caused a 3.5-fold elevation in serum alanine aminotransferase levels but the enzyme fell to control levels when BSO was included in the diet. L-Buthionine (S,R) sulfoximine administration also attenuated ethanol-induced steatosis, prevented the leakage of lysosomal cathepsins into the cytosol, and prevented the ethanol-elicited decline in proteasome activity.

CONCLUSIONS

L-Buthionine (S,R) sulfoximine, administered with ethanol, significantly depleted hepatic glutathione, compared with controls. However, despite the decrease in hepatic antioxidant levels, liver injury by ethanol was alleviated, due, in part, to a BSO-elicited acceleration of ethanol metabolism.

Ethanol-induced oxidative stress suppresses generation of peptides for antigen presentation by hepatoma cells

Processing of peptides for antigen presentation is catalyzed by antigen-trimming enzymes, including the proteasome and leucine aminopeptidase. Oxidative stress suppresses proteasome function. We hypothesized that in liver cells, processing of antigenic peptides is altered by ethanol metabolism. To address this issue, soluble extracts of ethanol-metabolizing VL-17A cells treated with 100 mM ethanol or left untreated were incubated with C-extended or N-extended 18-27 HBV core peptides. Peptide cleavage was measured by recovery after HPLC. Ethanol exposure to VL-17A cells increased CYP2E1 and decreased proteasome peptidase activities. The latter effect was prevented by treatment of cells with inhibitors, 4-methylpyrazole and diallyl sulfide. Ethanol treatment of VL-17A cells also reduced the activity of leucine aminopeptidase (LAP). Consequently, cleavage of both C-extended and N-extended peptides by cytosolic extracts was suppressed by pretreatment of cells with ethanol. Treatment of cells with interferon gamma, which enhances proteasome activity, did not reverse the effects of ethanol. Ethanol exerted similar effects on WIFB cells, indicating that its effects are not unique to one cell type.

CONCLUSION

Ethanol metabolism suppresses activities of antigen-trimming enzymes, thereby decreasing the cleavage of C-extended and N-extended peptides. This defect may potentially result in decreased MHC class I-restricted antigen presentation on virally infected liver cells.

Recombinant Hep G2 cells that express alcohol dehydrogenase and cytochrome P450 2E1 as a model of ethanol-elicited cytotoxicity

HepG2 cells were transfected with recombinant plasmids, one carrying the murine alcohol dehydrogenase (ADH) gene and the other containing the gene encoding human cytochrome P450 2E1 (CYP2E1). One of recombinant clones called VL-17A exhibited ADH and CYP2E1 specific activities comparable to those in isolated rat hepatocytes. VL-17A cells oxidized ethanol and generated acetaldehyde, the levels of which depended upon the initial ethanol concentration. Compared with unexposed VL-17A cells, ethanol exposure increased the cellular redox (lactate:pyruvate ratio) and caused cell toxicity, indicated by increased leakage of lactate dehydrogenase into the medium,. Exposure of VL-17A cells to 100mM ethanol significantly elevated caspase 3 activity, an indicator of apoptosis, but this ethanol concentration did not affect caspase 3 activity in parental HepG2 cells. Because ethanol consumption causes a decline in hepatic protein catabolism, we examined the influence of ethanol exposure on proteasome activity in HepG2, VL-17A, E-47 (CYP2E1(+)) and VA-13 (ADH(+)) cells. Exposure to 100mM ethanol caused a 25% decline in the chymotrypsin-like activity of the proteasome in VL-17A cells, but the enzyme was unaffected in the other cell types. This inhibitory effect on the proteasome was blocked when ethanol metabolism was blocked by 4-methyl pyrazole. We conclude that recombinant VL-17A cells, which express both ADH and CYP2E1 exhibit hepatocyte-like characteristics in response to ethanol. Furthermore, the metabolism of ethanol by these cells via ADH and CYP2E1 is sufficient to bring about an inhibition of proteasome activity that may lead to apoptotic cell death.

Ethanol metabolism alters interferon gamma signaling in recombinant HepG2 cells

We previously showed that IFNgamma signal transduction was suppressed by ethanol in recombinant HepG2 cells (VL-17A cells), which express alcohol dehydrogenase (ADH) and CYP2E1. We examined the mechanisms by which STAT1 phosphorylation is blocked by ethanol treatment in VL-17A cells. Cells were exposed to 0 or 100 mmol/L ethanol for 72 hours. STAT1 phosphorylation was determined by Western blot after 1 hour IFNgamma exposure. Reduction of STAT1 phosphorylation by ethanol was prevented in the presence of 4MP, DAS, or uric acid, indicating that the oxidative products from ethanol metabolism were partly responsible for suppression of STAT1 phosphorylation. Ethanol exposure decreased STAT1 tyrosine phosphorylation, whereas serine phosphorylation on the protein was unchanged. These effects of ethanol were mimicked by the peroxynitrite (PN) donor, SIN-1, which also blocked tyrosine, but not serine phosphorylation, on STAT1. When cells expressing either ADH (VA-13 cells) or CYP2E1 (E-47 cells) were exposed to ethanol, both ADH- and CYP2E1-generated products reduced STAT1 phosphorylation. In addition, SOCS1, a negative regulator of IFNgamma signaling and which is degraded by the proteasome, was stabilized by ethanol treatment, presumably because of inhibited proteasome activity. Furthermore, SIN-1 treatment elevated SOCS1 levels in VL-17A cells, indicating that PN has a role in SOCS1 elevation. In conclusion, under conditions of ethanol-elicited oxidative stress, PN prevents STAT1 phosphorylation by stabilization of SOCS1, and possibly by nitration of tyrosine residues in STAT1 protein.

Peroxynitrite alters the catalytic activity of rodent liver proteasome in vitro and in vivo

The proteasome is an important multicatalytic enzyme complex that degrades misfolded and oxidized proteins, signal transduction factors, and antigenic peptides for presentation. We investigated the in vitro effects of peroxynitrite (PN) on the peptidase activity of both crude 20S and 26S and purified 20S proteasome preparations from rat liver as well as proteasome activity in Hep G2 cells and in mouse liver. Crude and purified proteasome preparations were exposed to PN or to the PN donor, 3-morpholinosydnonimine hydrochloride (SIN-1), and then assayed for chymotrypsin-like activity. For in vivo experiments, mice were treated with molsidomine, which is metabolized to SIN-1 in liver. PN and SIN-1 dose-dependently modulated the chymotrypsin-like activity of the 20S proteasome: lower concentrations enhanced proteasome activity, and higher concentrations caused its decline. The NO donor S-nitroso-N-acetylpenicillamine (SNAP), at all concentrations, suppressed 20S proteasome activity. We observed similar results when liver soluble fractions (S-100) were treated with PN, SIN-1, or SNAP, except that enzyme activity in S-100 fractions was less sensitive than the purified enzymes to these agents. Treatment of Hep G2 cells with 0.01 or 0.1 mmol/L SIN-1 stimulated in situ proteasome activity in these cells, while 1 mmol/L SIN-1 suppressed it. SNAP treatment did not affect proteasome activity in Hep G2 cells. Mice treated with molsidomine had enhanced liver proteasome activity 6 hours after treatment, but after 24 hours enzyme activity declined below control levels. In conclusion, PN dose-dependently modulated proteasome activity, regulating protein degradation by the proteasome in liver cells.

Alcohol and HIV decrease proteasome and immunoproteasome function in macrophages: implications for impaired immune function during disease

Proteasomes (proteinase complexes, PR) and immunoproteasomes (IPR) degrade damaged proteins and affect protein processing required for antigen presentation by mononuclear phagocytes. These critical immune processes are attenuated during progressive HIV-1 infection and are affected by alcohol abuse. To investigate the mechanisms underlying these functional changes, we measured PR and CYP2E1 activities [an ethanol (EtOH) metabolizing enzyme] and reactive oxygen species (ROS) in human monocyte-derived macrophages (MDM) following HIV-1 infection and EtOH treatment. We observed progressive declines of PR activity and PR/IPR contents in HIV-1-infected MDM. PR activity and IPR expression increased after IFN-gamma stimulation but reduced after HIV-1 infection. EtOH inhibited both IFN-gamma-induced PR and IPR. Paradoxically, EtOH attenuated PR catalytic activity in infected MDM and suppressed viral replication. Elevated ROS followed EtOH exposure and paralleled decreased PR activity. The latter was restored by anti-oxidant. The data support the notion that HIV-1 infection and EtOH may work in concert to affect immune function including antigen presentation and thereby affect disease progression.

Interferon gamma enhances proteasome activity in recombinant Hep G2 cells that express cytochrome P4502E1: modulation by ethanol

We tested the influence of IFNgamma on proteasome activity in parental Hep G2 cells that do not metabolize ethanol, as well as in recombinant Hep G2-derived cells that express either or both alcohol dehydrogenase (ADH) and cytochrome P4502E1 (CYP2E1). IFNgamma treatment increased proteasome activity in VL-17A (ADH(+), CYP2E1(+)) and E-47 (CYP2E1(+)) cells, but not in Hep G2, VI-R2 (parental cells with empty vectors) or in VA-13 (ADH(+)) cells. Proteasome activation by IFNgamma correlated positively with the level of CYP2E1 activity. Treatment of VL-17A cells with agents that inhibit CYP2E1 or the inducible nitric oxide synthase (iNOS) or that prevent the formation of peroxynitrite also blocked proteasome activation by IFNgamma, indicating that the proteasome may be directly activated by products of CYP2E1 and iNOS catalysis. While IFNgamma treatment increased proteasome activity, it also decreased CYP2E1 activity. Both effects were mediated via the Janus kinase-signal transducer and activator of transcription 1 (JAK-STAT1) pathway, as both were blocked by the JAK2 inhibitor, tyrphostin AG 490. Ethanol treatment of VL-17A cells also caused a similar blockage of these same IFNgamma-mediated effects, by inhibiting STAT1 phosphorylation. This inhibition was largely due to ethanol metabolism, as 4-methylpyrazole, an ethanol metabolism inhibitor, restored IFNgamma-mediated STAT1 phosphorylation in ethanol-treated cells. Our results lead us to propose that IFNgamma initiates signal transduction, which alters the activities of CYP2E1 and iNOS, thereby producing reactive oxygen species. One of these oxidants, possibly peroxynitrite, may be directly involved in proteasome activation. Ethanol metabolism by VL-17A cells suppresses IFNgamma-mediated induction of proteasome activity, in part, by preventing STAT1 phosphorylation.

Alcohol consumption is associated with alterations in macrophage responses to interferon-gamma and infection by Salmonella typhimurium

Abuse of ethanol (EtOH) by human beings and administration of EtOH to experimental animals has been shown to be associated with a suppression of the immune system. Consumption of EtOH has also been associated with an increased incidence and severity of infections of human beings and experimental animals, which has been attributed to the immunosuppression associated with EtOH consumption. It has been shown that EtOH also affects the function of macrophages (MØ), which are important effector cells in the innate and adaptive immune responses to infectious agents. The present studies were designed to investigate the effects of EtOH on MØ function with an animal model of EtOH consumption. The experiments reported in this paper were done with inflammatory MØ and were designed to determine the effects of EtOH on the ability of inflammatory MØ to respond to interferon-gamma (IFN-gamma) to control the intracellular growth of Salmonella typhimurium, as well as the production of proinflammatory cytokines and nitric oxide. The ability of MØ from EtOH-fed mice to respond to bacterial endotoxin (lipopolysaccharide (LPS)) and IFN-gamma was also evaluated. MØ isolated from EtOH-fed mice did not respond as well to IFN-gamma as MØ isolated from control mice as measured by control of S. typhimurium, as well as tumor necrosis factor (TNF) and nitric oxide production. Interleukin (IL)-6 production was not affected. Activation of MØ from EtOH-fed mice with LPS and IFN-gamma produced levels of nitric oxide and TNF only slightly less than the levels seen in MØ from control mice, but a significant decrease in IL-6 was seen when MØ from EtOH-fed mice were stimulated with this combination. Flow cytometric analyses showed that IFN-gamma receptor expression was not affected by EtOH. Together the data presented in this paper show that consumption of EtOH is associated with changes in inflammatory MØ responses to IFN-gamma.

Regulation of IL-13 production by histamine in cloned murine T helper type 2 cells

Histamine affects the balance of T helper type 1 (Th1) and T helper type 2 (Th2) cytokines by shifting cytokine production from a Th1 to a Th2 pattern. Interleukin-13 (IL-13) is an important autacoid mediator that has been implicated in the development of allergic disease. This study was designed to investigate the mechanisms of regulation of IL-13 by histamine in Th2 cells. D10.G4.1 cells, a murine Th2 cell line, were treated with histamine (10(-8)-10(-4) M) and then activated with PMA (phorbol 12 myristate 13-acetate) plus ionomycin or alphaCD3. Levels of IL-13 production were then measured by enzyme-linked immunosorbent assay (ELISA) and semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). Cells were pretreated with histamine receptor antagonists pyrilamine, ranitidine, cimetidine and thioperamide to determine the involvement of histamine receptors. Cells were also pretreated with protein kinase A (PKA) inhibitors N-[2-(methylaminoethyl)]-5-isoquinoline-sulfonamide (H-8) and Rp-diastereomer of adenosine cyclic 3'5'-phosphorothionate (Rp-cAMPS), and Janus kinase-signal transducer and activator of transcription (Jak-STAT) inhibitor tyrphostin AG490 prior to the addition of histamine. H-8 is an inhibitor of the catalytic subunit of PKA while Rp-cAMPS is an inhibitor of the regulatory subunit of PKA. Tyrphostin is an inhibitor of Jak2, Jak3, STATI, STAT3 and STAT5. Finally, cells were pretreated with IL-12, a monokine known to repress STAT6 DNA binding. We found that histamine dose-dependently enhanced IL-13 secretion and mRNA levels in Th2 cells via H1 and H2 receptors. Pretreatment of cells with H-8, Rp-cAMPS and tyrphostin prevented histamine-induced secretion and transcription of IL-13. Likewise, pretreatment of Th2 cells with IL-12 also reversed histamine's effects on IL-13 secretion from stimulatory to inhibitory. These observations suggest a role for PKA and the Jak-STAT pathway in histamine-mediated elevation of IL-13 secretion and transcription.

Histamine utilizes JAK-STAT pathway in regulating cytokine production

Histamine shifts TH1/TH2 cytokine balance from TH1 to TH2 cytokines. The phosphorylation of STAT factors and their translocation to nucleus are important steps in the regulation of TH1/TH2 cytokine balance. This study was designed to investigate the effects of histamine on Janus kinases-signal transducers and activators of transcription (JAK-STAT) pathway. The splenocytes were treated with histamine in the presence or absence of JAK-STAT inhibitor, tyrphostin, activated with IFNgamma for 30 min, and phosphorylated STAT1 was detected by immunoblotting. We found that histamine up-regulated the phosphorylation of STATI and tyrphostin prevented this phosphorylation. We then studied the effects of tyrphostin on histamine-mediated inhibition of IFNgamma production and histamine-mediated stimulation of IL-5 and IL-10 production. Tyrphostin dose-dependently reversed the effects of histamine on IFNgamma, IL-5 and IL-10 production, as evident by ELISA. These observations suggest that histamine regulated JAK-STAT signal transduction, which is involved in cytokine secretion.

The effects of histamine on interferon gamma production are dependent on the stimulatory signals

Histamine regulates the immune response by enhancing TH2 cytokine production and by inhibiting TH1 cytokine production. We assessed the mechanisms of histamine's action on helper T cell subsets by evaluating the role of protein kinase A (PKA) in the histamine-mediated effects on IFN gamma production. The splenocytes and TH1 murine cloned cells (pGL10) were pretreated with histamine at a concentration range of 10(-8)-10(-5) M for 1 h and then were activated with anti-CD3, PHA, PMA + ionomycin, or ionomycin for 24 h. The levels of IFN gamma were measured in the supernatants by ELISA. The inhibitory effects of histamine were the most prominent in anti-CD3-stimulated splenocytes (61%). The effects of histamine on IFN gamma production from TH1 cells depended on the mode of cell activation. The activation of cells with anti-CD3 resulted in 27% inhibition of IFN gamma production whereas the activation with ionomycin produced 70% suppression. The inhibitory effects of histamine were completely reversed by cimetidine in a dose-dependent manner in both TH1 cells and in splenocytes. PKA played a role in the inhibition of IFN gamma by histamine when the cells were activated via TCR, and the PKA inhibitors Rp-cAMPS (10(-5) M) and H8 (10(-5) M) reversed the inhibitory effects of histamine on IFN gamma production. However, when the cells were stimulated with ionomycin, the PKA inhibitors did not affect histamine-mediated suppression of IFN gamma production.

Regulation of interleukin-10 secretion by histamine in TH2 cells and splenocytes

Interleukin-10 is a potent suppressive factor that down-regulates cellular immune response via inhibition of the production of TH1 cytokines. Histamine shifts the TH1/TH2 balance from TH1 to TH2 cytokines making the effects of histamine on IL-10 secretion an important factor in this switch. This study was designed to assess the role of histamine in the regulation of IL-10 production and the involvement of PKA and STAT factors in this process. TH2 cells (D10.G4.1) and AKR/j splenocytes were pretreated with histamine at a concentration range of 10(-8)-10(-5) M for 1 h and then activated with PMA + ionomycin or anti-CD3 for 24 h. The supernatants were collected and tested for IL-10 content by ELISA. Histamine stimulated IL-10 production in TH2 cells in a dose-dependent manner that was reversed by both H1- and H2-receptor antagonists and by PKA inhibitors H8 and Rp-cAMPS. Tyrphostin also reversed the stimulation of IL-10 secretion by histamine, indicating that STAT factors were involved in this process. The up-regulation of IL-10 production by histamine in splenocytes was accompanied by inhibitory effects of histamine on IFN gamma production. The pretreatment of splenocytes with histamine in the presence of anti-IL-10 abrogated histamine-mediated inhibition of IFN gamma production suggesting that the effects of histamine on IFN gamma secretion were regulated by IL-10 in multi-cell system.

Investigation of K+ channel expression in human peripheral lymphocytes of healthy donors by means of flow cytometry

Evaluation of different types of K+ channel expression was performed in resting and PHA (phytohemagglutinine)-activated human peripheral lymphocytes (HPL) of healthy donors by means of flow cytometry. In resting peripheral lymphocytes, the application of kaliotoxin (a selective blocker for voltage-dependent K+ (K(V)) channels), K(V) resulted in pronounced depolarization of lymphocyte membrane potential, with further promotion in the presence of thapsigargin (compound discharging Ca(i) from endoplasmic reticulum). In activated HPL, the expression of various types of K+ channels was estimated utilizing cell-cycle analysis data. In contrast to the resting cells, kaliotoxin-induced depolarization of membrane potential in PHA-activated lymphocytes of the G0/G1 phase was not enhanced by thapsigargin and in PHA-activated lymphocytes of the S and G2/M phases we were able to observe repolarization of membrane potential after kaliotoxin-induced depolarization of membrane potential. Substitution of kaliotoxin for charybdotoxin (a non-selective drug blocking both K(V) and K(Ca) channels) abrogated the above effects in PHA-activated lymphocytes. Thus, K(V) channels are active in both resting and activated HPLs and K(Ca) channel expression occurs with cell-cycle progress on PHA-induced activation of peripheral lymphocytes.

Immunoregulatory effects of N9-benzyl- and N7-benzyl-8-bromoguanines

In this study we investigated the effects of two guanine derivatives, 9-benzyl- (I) and 7-benzyl-8-bromoguanines (II) on the proliferation of human T-cell leukemia and T-cell lymphoma, normal human peripheral blood mononuclear cells (PBMC), and mouse Th1 (pGL10) and Th2 (D10.G4.1) clones. We also assessed their effects on cytokine production (IL-3, IL-10 and IFN-gamma) in PBMC, T-cell lymphoma, HUT78 (IL-2), and murine Th1 (IL-2) and Th2 (IL-4 and IL-5) clones. These compounds were synthesize as analog of known inhibitors of purine nucleoside phosphorylase (PNP) 8-amino-9-benzylguanine. These compounds suppressed proliferation of human leukemia MOLT-4 cells, human cutaneous lymphoma HUT78 cells and normal PMBC. Compound II was a significantly more potent inhibitor than compound I. Exogenous recombinant human IL-2 reversed the anti-proliferative effects of both compounds on HUT78 cells. These compounds had low toxicity to human EBV-transformed B-lymphocytes. Both compounds suppressed the production of IL-2 by activated human HUT78 cells, IFN-gamma by PBMC and did not affect IL-3 and IL-10 production in PBMC. Compound I inhibited anti-CD3-activated IL-2 secretion from the murine Th1 clone. The murine Th2 clone was less sensitive to both compounds as compared with Thl. The production of IL-4 and IL-5 by this clone was not suppressed. Thus, it has been shown that not only 9-substituted guanines but also their 7-isomers selectively inhibit T-cell functions and both selectively inhibit Th1-related cytokines secretion.

Chronic hepatitis C: T-helper1/T-helper2 imbalance could cause virus persistence in peripheral blood

Interferon gamma (IFN gamma) and interleukin 4, 10 and 12 (IL-4, -10, -12) production was measured in whole peripheral blood (WPB) and peripheral blood mononuclear cells (PBMC) of 10 chronic hepatitis C (CHC) patients. The level of IFN gamma in supernatants in mitogen-activated WPB was lower than in healthy donors. IL-10 served as a possible downregulative factor for IFN gamma, since its spontaneous IL-10 production was enhanced in CHC. Neutralization of IL-10 partly restored IFN gamma response in CHC patients. Recombinant IL-12 (rIL-12) also enhanced IFN gamma of CHC patients, but IL-12 production was decreased in CHC. Thus, IFN gamma production deficiency in CHC patients is secondary to blockage by high levels of IL-10-impaired IL-12 production.

Interferon gamma production in whole peripheral blood culture in acute hepatitis B

Interferon gamma (IFNg) production in whole peripheral blood (WPB) and mononuclear (MN) cell culture in acute hepatitis B (AHB) was compared. IFNg production was induced by phytogem agglutinin and measured in the cell supernatants of 14 AHB patients in the course of the disease. There were some up-regulating factors of IFNg production that probably operated in WPB culture: the presence of autoerythrocytes as well as the low content of monocytes. Autoserum regulated IFNg production in a stage-dependent way: it decreased IFNg activity at the bilirubin peak in hepatitis B infection, but not in convalescence. In contrast, we did not find a serum blocking effect in the corresponding stage of acute hepatitis A. The nature of this serum blocking factor in AHB is unclear.

[Immune response and the dynamics of the cytolysis syndrome in viral hepatitis A and B]

Forty-nine patients with acute viral hepatitis A and B were examined for the relationship of the blood content of individual lymphocyte subpopulations at the height of the disease to subsequent duration of the cytolytic syndrome (high activity of ALT). The duration of the cytolytic syndrome associated with viral hepatitis A was reversely related to the content of B lymphocytes and when associated with viral hepatitis B to the content of T cells--immunoregulator precursors (autorosette-forming cells). In both patterns of viral hepatitis, the duration of the cytolytic syndrome did not depend on the rate of lymphocyte sensitization to the inducer antigens (HAVAg, kHBsAg). Unlike viral hepatitis A, the duration of the cytolytic syndrome in viral hepatitis B was directly related to the rate of lymphocyte sensitization to hepatic lipoprotein.

[Characteristics of immune response regulation in viral hepatitis A and B]

In 272 patients with virus hepatitis A and B the content of theophylline-sensitive lymphocytes (T-suppressors) and theophylline-resistant lymphocytes (T-helpers) in the peripheral blood was determined. Differences in the content of T-suppressors in cases of acute virus hepatitis A and B with an equal degree of severity were revealed: at the peak of hepatitis A infection in the mild form of the disease the number of the cells was decreased, while at the peak of hepatitis B infection an increase in their number was observed in the mild and moderate forms of the disease and a decrease, in the severe form of the disease. In chronic persistent hepatitis a decrease in the content of T-suppressors and an increase in the content of T-helpers were observed, and in chronic active hepatitis (at the period of remission) and increase in the T-helpers occurred. Changes in the content of the cells of both types are not characteristic of HBsAg carriership.

[Changes in the count of highly avid, thermostable blood T-cells in viral hepatitis and its outcome]

The determination of the content of thermostable T-lymphocytes in the peripheral blood in 184 patients with acute virus hepatitis, as well as at the stage of the termination of the disease, has revealed the increased number of cells belonging to this subpopulation in all the groups under study. At the acute stage of the disease a rise in the number of thermostable T-cells is directly related to the severity of the process. Of different variants of the termination of hepatitis B, the highest content of thermostable T-cells is observed in chronic active hepatitis and chronic HBsAg carriership, while in chronic persistent hepatitis the content of thermostable T-cells is considerably lower.