Effects of coxsackievirus B3 infection on the acute-phase protein metallothionein and on cytochrome P-4501A1 involved in the detoxification processes of TCDD in the mouse

The Role of Cytochrome P450 Enzymes in COVID-19 Pathogenesis and Therapy

Coronavirus disease 2019 (COVID-19) has become a new public health crisis threatening the world. Dysregulated immune responses are the most striking pathophysiological features of patients with severe COVID-19, which can result in multiple-organ failure and death. The cytochrome P450 (CYP) system is the most important drug metabolizing enzyme family, which plays a significant role in the metabolism of endogenous or exogenous substances. Endogenous CYPs participate in the biosynthesis or catabolism of endogenous substances, including steroids, vitamins, eicosanoids, and fatty acids, whilst xenobiotic CYPs are associated with the metabolism of environmental toxins, drugs, and carcinogens. CYP expression and activity are greatly affected by immune response. However, changes in CYP expression and/or function in COVID-19 and their impact on COVID-19 pathophysiology and the metabolism of therapeutic agents in COVID-19, remain unclear. In this analysis, we review current evidence predominantly in the following areas: firstly, the possible changes in CYP expression and/or function in COVID-19; secondly, the effects of CYPs on the metabolism of arachidonic acid, vitamins, and steroid hormones in COVID-19; and thirdly, the effects of CYPs on the metabolism of therapeutic COVID-19 drugs.

TCDD-mediated suppression of the in vitro anti-sheep erythrocyte IgM antibody forming cell response is reversed by interferon-gamma

Suppression of humoral immune responses by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been well established to require the aryl hydrocarbon receptor; however, the downstream mechanisms for this immunotoxic response remain poorly understood. Based on evidence demonstrating that primary hepatocytes pretreated with interferon-gamma (IFN-gamma) exhibited decreased induction of cytochrome P450 1A1 (CYP1A1) by TCDD, and that serum factors alter the sensitivity of the in vitro T-cell-dependent IgM antibody forming cell (AFC) response, it was hypothesized that IFN-gamma attenuates suppression of humoral immune responses by TCDD. In fact, concomitant addition of IFN-gamma (100 U/ml) produced a concentration-related attenuation of TCDD-mediated suppression of the anti-sheep erythrocyte (anti-sRBC) IgM AFC response. Time-of-addition studies performed by adding 100 U/ml IFN-gamma at 0, 1, 2, 4, 12, 24, 48, and 72 h post-TCDD showed that suppression of the AFC response was prevented only when IFN-gamma was added within 2 h of TCDD treatment. mRNA levels of the IgM components, immunoglobulin kappa light chain, immunoglobulin mu heavy chain, and immunoglobulin J-chain were significantly decreased by TCDD treatment, an effect that was completely reversed by IFN-gamma (100 U/ml) cotreatment. Further studies showed that IFN-alpha, IFN-beta, and IFN-gamma significantly attenuate TCDD-induced increases in CYP1A1 mRNA levels to varying degrees, but concentrations as high as 1000 U/ml of type I IFNs did not reverse the effect of TCDD on the anti-sRBC IgM AFC response. In summary, IFN-gamma prevents TCDD-mediated suppression of the IgM AFC response in a concentration- and time-related manner by altering transcriptional effects associated with TCDD treatment.

Polybrominated diphenyl ether exposure suppresses cytokines important in the defence to coxsackievirus B3 infection in mice

Environmental pollutants can adversely affect the immune system. The host defence during infection depends on cytokine signalling and proper function of immune cells. However, no studies have addressed how polybrominated diphenyl ethers (PBDEs) affect cytokine responses. We investigated the combined effects in Balb/c mice of human coxsackievirus B3 (CVB3) infection and exposure to PBDEs (BDE-99 or Bromkal mixture) on 21 serum cytokines. The mice were infected (i.p.) on day 0, orally treated with BDE-99 or Bromkal on day 1 (20mg/kg bw) and put to death on day 3. CVB3 was quantitatively measured in the liver and pancreas by RT-PCR. The Luminex 200 multi-analyte system was used for cytokine analysis. High numbers of viral copies were found in the liver and pancreas. Infection increased TNF-alpha, IL-6, MCP-1, IL-12p40, KC and RANTES levels. Notably, PBDE-exposure resulted in a marked decrease, or even lack, of IL-13, MIP-1beta, RANTES, IFN-gamma and KC levels in non-infected mice. However, the effects of PBDE-exposure on cytokines did not affect viral replication during early CVB3 infection. In conclusion, PBDEs causes a selective block in immune signalling pathways but the consequences of this need to be further studied in different host resistance models of infection.

Molecular Mechanisms of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin Cardiovascular Embryotoxicity

2,3,7,8 Tetrachlorodibenzo-p-dioxin (TCDD) and related planar halogenated aromatic hydrocarbons are widespread environmental contaminants and potent developmental toxicants. Hallmarks of embryonic exposure include edema, hemorrhage, and mortality. Recent studies in zebrafish and chicken have revealed direct impairment of cardiac muscle growth that may underlie these overt symptoms. TCDD toxicity is mediated by the aryl hydrocarbon receptor, but downstream targets remain unclear. Oxidative stress and growth factor modulation have been implicated in TCDD cardiovascular toxicity. Gene expression profiling is elucidating additional pathways by which TCDD might act. We review our understanding of the mechanism of TCDD embryotoxicity at morphological and molecular levels.

Interactions among infections, nutrients and xenobiotics

During recent years there have been several incidents in which symptoms of disease have been linked to consumption of food contaminated by chemical substances (e.g., 2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD). Furthermore, outbreaks of infections in food-producing animals have attracted major attention regarding the safety of consumers, e.g., Bovine Spongiform Encephalitis (BSE) and influenza in chicken. As shown for several xenobiotics in an increasing number of experimental studies, even low-dose xenobiotic exposure may impair immune function over time, as well as microorganism virulence, resulting in more severe infectious diseases and associated complications. Moreover, during ongoing infection, xenobiotic uptake and distribution are often changed resulting in increased toxic insult to the host. The interactions among infectious agents, nutrients, and xenobiotics have thus become a developing concern and new avenue of research in food toxicology as well as in food-borne diseases. From a health perspective, in the risk assessment of xenobiotics in our food and environment, synergistic effects among microorganisms, nutrients, and xenobiotics will have to be considered. Otherwise, such effects may gradually change the disease panorama in society.

Anti-parasite treatment removes negative effects of environmental pollutants on reproduction in an Arctic seabird

Recent studies have shown that the detrimental effects of anthropogenic pollutants may be worse if organisms are exposed to natural stress. In this study, we examined whether negative effects of organochlorines (OCs) could be influenced by parasites. In two breeding seasons, we administered an anti-helminthic drug to groups of breeding glaucous gulls (Larus hyperboreus), whereas control groups were placebo treated. In all birds, blood residues of the most important OCs in the study population (hexachlorobenzene, oxychlordane, p,p'-dichlorodiphenyldichloroethylene and polychlorinated biphenyl), were measured. The relationships between OCs and fitness components (i.e. nesting success and return rate between breeding seasons) were then compared between the birds receiving anti-parasite treatment and the controls. Among untreated males, higher blood residues of OCs were associated with lowered nesting success, while in males receiving anti-parasite treatment, there was no detrimental effect of OCs on fitness. Return rate was not affected by treatment or OCs. Our findings suggest that parasites may be an important factor in triggering reproductive effects of such pollutants, and that relatively low levels of OCs may have serious reproductive consequences in natural populations when stress from other sources is high.

Iron and copper accumulation in the brain of coxsackievirus-infected mice exposed to cadmium

Cadmium (Cd) is a potentially toxic metal widely distributed in the environment and known to cause adverse health effects in humans. During coxsackievirus infection, the concentrations of essential and nonessential trace elements (e.g., iron (Fe), copper (Cu), and Cd) change in different target organs of the infection. Fe and Cu are recognized cofactors in host defence reactions, and Fe is known to be associated with certain pathological conditions of the brain. However, whether nonessential trace elements could influence the balance of essential trace elements in the brain is unknown. In this study the brain Fe, Cu, and Cd contents were measured through inductively coupled plasma mass spectrometry and their distributions determined by nuclear microscopy in the early phase (day 3) of coxsackievirus B3 (CB3) infection in nonexposed and in Cd-exposed female Balb/c mice. In CB3 infection the brain is a well-known target that has not been studied with regard to trace element balance. The brain concentration of Cu compared with that of noninfected control mice was increased by 9% (P < 0.05) in infected mice not exposed to Cd and by 10% (not significant) in infected Cd-exposed mice. A similar response was seen for Fe, which in infected Cd-exposed mice, compared to noninfected control mice, tended to increase by 16%. Cu showed an even tissue distribution, whereas Fe was distributed in focal deposits. Changes in Cd concentration in the brain of infected mice were less consistent but evenly distributed. Further studies are needed to define whether the accumulation and distribution of trace elements in the brain have an impact on brain function.

Acrylamide tissue distribution and genotoxic effects in a common viral infection in mice

Acrylamide (AA) has been shown to cause neurotoxic effects in humans and neurotoxic, genotoxic, reproductive, and carcinogenic effects in laboratory animals. Infection with the human coxsackievirus B3 (CB3) in the murine model results in changed uptake and tissue distribution of several environmental pollutants, which may result in aggravated disease. In the present study female Balb/c mice were infected with CB3, and on day 1 of the infection, dosed orally with approximately 50 microg/kg bw of [(14)C]acrylamide ((14)AA) and subsequently sacrificed on day 3 of the infection for studies of the distribution of radioactivity and genotoxic effects in terms of the frequency of micronucleated erythrocytes. Infected mice developed an expected clinical signs of disease. The infection decreased the radioactivity by 45% (p<0.05) in the pancreas but increased it by 70% (p<0.05) in the blood and more than two-fold in the thymus (p<0.01). However, the infection caused no changes in the radioactivity in the brain, heart, liver, lungs, spleen, or kidneys. As a response to the infection the proportion of young red blood cells (PCE) decreased to about a third (p<0.001) of that in the control mice, but no genotoxic effects were observed. Thus, the tissue radioactivity after (14)AA administration indicated an infection-induced change in the metabolism of AA, the exact pathogenic interpretation of which warrants further studies.

Common viral infection affects pentabrominated diphenyl ether (PBDE) distribution and metabolic and hormonal activities in mice

A murine model infection with the human coxsackievirus B3 (CB3) has been shown to change uptake and tissue distribution of several environmental pollutants, in some cases followed by an aggravated disease. In this study, the model was tested for polybrominated diphenyl ethers (PBDEs), which we know are absorbed from the gastro-intestinal tract and further distributed throughout the body. On day 0, female Balb/c mice were infected with CB3; on day 1 of the infection, they were dosed orally with approximately 200 microg/kgbody weight (bw) (ca. 0.52 microCi) of 14C-labelled 2,2',4,4',5-pentabromodiphenyl ether (14C-BDE-99); and on day 3 of the infection, they were sacrificed for studies of 14C-BDE-99 distribution. In comparison with control values, 14C-BDE-99 concentrations were altered in the liver (186%, p < 0.05), lungs (47%, p < 0.05) and pancreas (51%, p < 0.05), but no change was seen in the blood, brain, heart, spleen, thymus or kidneys. Moreover, on day 3, plasma thyroxine (T4) levels (33%, p < 0.001), as well as ethoxyresorufin-O-dealkylase (EROD) (17%, p < 0.001) and pentoxyresorufin O-dealkylase (PROD) (31%, p < 0.001) activities were much lower in infected compared to non-infected control mice. It is suggested that the change in tissue distribution of 14C-BDE-99 as a result of the infection may be caused by an infection-induced specific change in the hepatic enzyme activities affecting this PBDE congener. The mechanism for virally induced T4 changes remains, however, unclear. The presented infection-induced alteration in distribution, which is different from other environmental pollutants (e.g., dioxin, acrylamide and cadmium), may have consequences for PBDEs toxicity, especially in relation to microsomal enzyme and thyroid hormone activities.

Metallothionein is induced and trace element balance changed in target organs of a common viral infection

In experimental studies on the common human coxsackievirus B type 3 (CB3) infection, administered cadmium (Cd) is known to accumulate in the liver and kidneys. CB3 adapted to Balb/c mice was used to study whether infection affects the Cd-binding protein, metallothionein (MT) and if this alters the normal physiological trace element balance in the liver, kidney, spleen and brain. On day 3 of infection, degradation of liver proteins (44%, P<0.01) occurred, whereas in the spleen, protein increased (63%, P<0.05). The infection increased MT five-fold (P<0.01) in liver and kidneys, and in spleen by 34% (P<0.05). A redistribution of Cd and copper (Cu) from the liver to the kidney was associated with this increase in MT, resulting in an increased (P<0.01) kidney/liver ratio for both elements. The infection increased the zinc (Zn) concentration more in the kidney than in the liver, but the kidney/liver ratio was not significantly affected. Results show that MT is increased in several organs during the early phase of infection and is associated with redistribution of both essential and non-essential trace elements. This may be a normal response in common infections that could adversely influence the pathogenesis when the host is concomitantly exposed to potentially toxic trace elements, even at levels in the physiological range.

Trace element changes in the pancreas during viral infection in mice

INTRODUCTION

The trigger for some cases of juvenile diabetes has been suggested to be an interaction between a virus and various trace elements. Infection with human coxsackievirus B3 (CB3) in the murine model results in viral replication and inflammation in the pancreas.

AIM

To determine how infection affects the trace element balance in the pancreas.

METHODOLOGY

Concentrations of the following trace elements were measured in the serum and pancreas during the early phase (days 1 and 3) of CB3 infection in female Balb/c mice: aluminium, arsenic, cadmium (Cd), calcium (Ca), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), magnesium (Mg), manganese (Mn), mercury (Hg), selenium, silver, vanadium (V), and zinc (Zn). The trace element concentrations were measured through inductively coupled plasma mass spectrometry. The histopathology was established by hematoxylin-eosin techniques and immunohistochemical staining of both CD4 and CD8 cells of the pancreas.

RESULTS

Infected mice developed expected clinical signs of disease. The only changes at day 1 occurred in the serum, with a pronounced decrease in the Zn concentration and a small increase in the V concentration. At day 3, concentrations of several trace elements, including Cu, Zn, Fe, Ca, V, and Mn, showed pronounced changes in both the serum and the pancreas. Ca, Cu, Mg, Mn, and V, but none of the potentially toxic elements, accumulated in the pancreas. Cu and V concentrations increased in the serum as well.

CONCLUSION

Several trace element changes, preceding the development of pancreatitis, occurred in the pancreas in this viral infection, the exact pathogenic interpretation of which warrants further studies.

Effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin on trace elements, inflammation and viral clearance in the myocardium during coxsackievirus B3 infection in mice

A myocarditic coxsackievirus B3 (CB3) infection in adult male A/J mice was used to investigate the effects of 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD) exposure on mortality and on inflammatory lesion, virus and trace element contents of the heart. The mice were injected with four weekly intraperitoneal (i.p.) injections of TCDD (a loading dose of 5 microg/kg followed by three maintenance doses of 1.4 microg/kg). To reach a steady-state body burden of TCDD the mice were allowed a 90-day recovery period before infection with CB3 virus. TCDD increased the infection-induced mortality rate, whereas in TCDD-exposed mice, heart lesions at day 7 after the virus inoculation (median value 0.67% of the tissue section area; interquartile range 0.28; not statistically significant) were one-third of that in non-exposed infected mice (2.07% of the tissue section area; interquartile range 3.06). The size of the inflammatory heart lesion correlated to the amount of virus (r(s) = 0.829, P < 0.01) as well as to the calcium (Ca: r(s) = 0.725, P < 0.01) and the magnesium (Mg: r(s) = -0.615, P < 0.05) contents. In TCDD-exposed mice in situ hybridisation of viral RNA in the myocardium at day 7 showed a tendency to decreased amounts of virus, as well as a less pronounced increase in myocardial Ca content, both supporting a milder myocardial disease after TCDD exposure. No effect of TCDD exposure was seen on the zinc (Zn) or selenium (Se) levels in the myocardium. In conclusion, although TCDD seemed to have a limiting effect on viral replication and the development of the inflammatory lesion in the myocardium, mortality was increased by TCDD in this infection model. However, TCDD had no significant effects on the selected trace elements that could be of importance for the severity of the inflammatory lesion (Ca, Se), for the local host response activation (Zn) or for the development of myocardial disease complications (Mg). Accordingly, the increased mortality may be a result of an infection-induced increase in TCDD toxicity to vital organs other than the heart, and/or a TCDD-induced change in the tissue affinity and virulence of the virus, possibly causing involvement of other target organs in the infectious process and changed pathogenesis.