Jelena Tomac

Liver fibrosis in mice induced by carbon tetrachloride and its reversion by luteolin

Hepatic fibrosis is effusive wound healing process in which excessive connective tissue builds up in the liver. Because specific treatments to stop progressive fibrosis of the liver are not available, we have investigated the effects of luteolin on carbon tetrachloride (CCl(4))-induced hepatic fibrosis. Male Balb/C mice were treated with CCl(4) (0.4 ml/kg) intraperitoneally (i.p.), twice a week for 6 weeks. Luteolin was administered i.p. once daily for next 2 weeks, in doses of 10, 25, and 50 mg/kg of body weight. The CCl(4) control group has been observed for spontaneous reversion of fibrosis. CCl(4)-intoxication increased serum aminotransferase and alkaline phosphatase levels and disturbed hepatic antioxidative status. Most of these parameters were spontaneously normalized in the CCl(4) control group, although the progression of liver fibrosis was observed histologically. Luteolin treatment has increased hepatic matrix metalloproteinase-9 levels and metallothionein (MT) I/II expression, eliminated fibrinous deposits and restored architecture of the liver in a dose-dependent manner. Concomitantly, the expression of glial fibrillary acidic protein and alpha-smooth muscle actin indicated deactivation of hepatic stellate cells. Our results suggest the therapeutic effects of luteolin on CCl(4)-induced liver fibrosis by promoting extracellular matrix degradation in the fibrotic liver tissue and the strong enhancement of hepatic regenerative capability, with MTs as a critical mediator of liver regeneration.

Passive Immunization Reduces Murine Cytomegalovirus-Induced Brain Pathology in Newborn Mice

ABSTRACT Human cytomegalovirus (HCMV) is the most frequent cause of congenital viral infections in humans and frequently leads to long-term central nervous system (CNS) abnormalities that include learning disabilities, microcephaly, and hearing loss. The pathogenesis of the CNS infection has not been fully elucidated and may arise as a result of direct damage of CMV-infected neurons or indirectly secondary to inflammatory response to infection. We used a recently established model of mouse CMV (MCMV) infection in newborn mice to analyze the contribution of humoral immunity to virus clearance from the brain. In brains of MCMV-infected newborn mice treated with immune serum, the titer of infectious virus was reduced below detection limit, whereas in the brains of mice receiving control (nonimmune) serum significant amounts of virus were recovered. Moreover, histopathological and immunohistological analyses revealed significantly less CNS inflammation in mice treated with immune serum. Treatment with MCMV-specific monoclonal antibodies also resulted in the reduction of virus titer in the brain. Recipients of control serum or irrelevant antibodies had more viral foci, marked mononuclear cell infiltrates, and prominent glial nodules in their brains than mice treated with immune serum or MCMV-specific antibodies. In conclusion, our data indicate that virus-specific antibodies have a protective role in the development of CNS pathology in MCMV-infected newborn mice, suggesting that antiviral antibodies may be an important component of protective immunological responses during CMV infection of the developing CNS.

Altered development of the brain after focal herpesvirus infection of the central nervous system

Human cytomegalovirus infection of the developing central nervous system (CNS) is a major cause of neurological damage in newborn infants and children. To investigate the pathogenesis of this human infection, we developed a mouse model of infection in the developing CNS. Intraperitoneal inoculation of newborn animals with murine cytomegalovirus resulted in virus replication in the liver followed by virus spread to the brain. Virus infection of the CNS was associated with the induction of inflammatory responses, including the induction of a large number of interferon-stimulated genes and histological evidence of focal encephalitis with recruitment of mononuclear cells to foci containing virus-infected cells. The morphogenesis of the cerebellum was delayed in infected animals. The defects in cerebellar development in infected animals were generalized and, although correlated temporally with virus replication and CNS inflammation, spatially unrelated to foci of virus-infected cells. Specific defects included decreased granular neuron proliferation and migration, expression of differentiation markers, and activation of neurotrophin receptors. These findings suggested that in the developing CNS, focal virus infection and induction of inflammatory responses in resident and infiltrating mononuclear cells resulted in delayed cerebellar morphogenesis.

Immune responses and cytokine induction in the development of severe hepatitis during acute infections with murine cytomegalovirus.

Summary. Salivary gland-derived murine cytomegalovirus (SGV) infections of mice have been widely used as models of human cytomegalovirus infections and in the study of CMV biology. Still, many aspects of SGV pathogenesis are not clearly defined. Fatal and non-fatal SGV infections were investigated to characterize pathogenetic correlates of mortality and to assess the role of the immune response in disease progression. Suppression of immune responses was observed in both lethal and sublethal infections. Depletion of immune cell populations in spleen, however, correlated with severe CMV-induced hepatitis and mortality. In addition, T cell depletion studies indicated a requirement for this immune cell subset in control of liver damage and survival of infected mice. Examination of cytokine responses revealed a previously undescribed shock-like syndrome in lethally-infected mice characterized by high levels of tumor necrosis factor α and interferon γ. Furthermore, the sites of tumor necrosis factor α gene induction did not strictly correlate with either viral load or the sites of tissue damage during infection. Taken together, these findings define the pathogenetic progression of disease as it relates to disease outcome and suggests that organ-specific differences in cytokine induction play a significant role in the late stages of acute lethal MCMV infections.

Metallothionein expression and tissue metal kinetics after partial hepatectomy in mice

To better elucidate previous results showing that partial hepatectomy noticeably changes the tissue content of zinc, calcium, magnesium, and iron(II) ions in regenerating the liver, thymus, and spleen, we report on the correlation of these metal tissue kinetics in these organs with the expression of metallothionein-I+II (MT-I+II) proteins and MT-I mRNA in early postoperative period (1, 2, 6, 12, and 24 h) after one-third hepatectomy (pHx). The results showed that 2 h after pHx the regenerating liver accumulated Zn2+, Ca2+, Mg2+, and Fe2+ ions while decreasing the concentration of all these metals in the spleen and of Zn2+ in the thymus. On the 24th h, a new high accumulation of Zn2+ and Ca2+ was seen in the regenerating liver and of Zn2+, Ca2+, and Fe2+ in the spleen. Simultaneously, MT-I mRNA increased in the liver and spleen. In hepatocytes and on several spleen and thymus mononuclear lymphatic cells, the increased expression of MT proteins was found mainly in the cytoplasm and nuclei. The areas expressing MTs in regenerating liver inversely correlated with those containing apoptotic cells, suggesting that these proteins participate in tissue restoration through reduction or increase of metal ions after injury to the liver.

The specific NK cell response in concert with perforin prevents CD8+ T cell-mediated immunopathology after mouse cytomegalovirus infection

Abstract Natural killer (NK) and CD8+ T cells play a crucial role in the control of mouse cytomegalovirus (MCMV) infection. These effector cells exert their functions by releasing antiviral cytokines and by cytolytic mechanisms including perforin activation. In addition to their role in virus control, NK cells play an immunoregulatory role since they shape the CD8+ T cell response to MCMV. To investigate the role of perforin-dependent cytolytic mechanism in NK cell modulation of CD8+ T cell response during acute MCMV infection, we have used perforin-deficient C57BL/6 mice (Prf1−/−) and have shown that virus control by CD8+ T cells in Prf1−/− mice is more efficient if NK cells are activated by the engagement of the Ly49H receptor with the m157 MCMV protein. A lack of perforin results in severe liver inflammation after MCMV infection, which is characterized by immunopathological lesions that are more pronounced in Prf1−/− mice infected with virus unable to activate NK cells. This immunopathology is caused by an abundant infiltration of activated CD8+ T cells. The depletion of CD8+ T cells has markedly reduced pathohistological lesions in the liver and improved the survival of Prf1−/− mice in spite of an increased viral load. Altogether, the results of our study suggest that a lack of perforin and absence of the specific activation of NK cells during acute MCMV infection lead to an unleashed CD8+ T cell response that is detrimental for the host.

Pathogenesis of Murine Cytomegalovirus Infection in Neonatal Mice

Cytomegalovirus (CMV) infections are a major cause of morbidity and mortality in congenitally and perinatally- infected infants. Despite the extensive characterisation of clinical disease induced by human CMV in neonatal infections in humans, fundamental questions regarding the pathogenesis of disease remain unanswered. For example , which tissues suport virus replication and what is the nature of tissue damage? What is the role of immune response and cytokines in protection from or exacerbation of disease? Also, which viral determinants are essential to virulence and how does at acquisition influence virulence? To begin to adress these issues, we have establishes a model of disease in neonatal mice using both virulent and attenuated strains of murine CMV. Our aproach to the study of MCMV pathogenesis in newborns is was a comparative one, in which infection with tissue culture derived virus was compared with an attenuated recombinant mutant lacking the fcr gene product. Investigation of MCMVpathogenesis in neonatal mice revealed several important aspects of disease. First, neonatal infection with WT virus followe a virulent disease course involving multiple tissues and organs. Absence of fcr gene product, however, results in significant attenuation of disease course. Second, virus replication and damage in the brain and meminges was a primary feature of infection and was unique to newborn mice. Third, this study implicates immunopathological mechanisms of disease booth in the CNS (neurovirulence), and in peripheral tissues and organs, especially the heart and conective tissues. In adition to morphological evidencesupporting immunopathology in neonatal infections, the dramatic induction of TNF-aassociated with the virulent WT virus also supports an immunopathological condition occuring in these mice

Brain-resident memory CD8+ T cells induced by congenital CMV infection prevent brain pathology and virus reactivation

Congenital HCMV infection is a leading infectious cause of long‐term neurodevelopmental sequelae. Infection of newborn mice with mouse cytomegalovirus (MCMV) intraperitoneally is a well‐established model of congenital human cytomegalovirus infection, which best recapitulates the hematogenous route of virus spread to brain and subsequent pathology. Here, we used this model to investigate the role, dynamics, and phenotype of CD8+ T cells in the brain following infection of newborn mice. We show that CD8+ T cells infiltrate the brain and form a pool of tissue‐resident memory T cells (TRM cells) that persist for lifetime. Adoptively transferred virus‐specific CD8+ T cells provide protection against primary MCMV infection in newborn mice, reduce brain pathology, and remain in the brain as TRM cells. Brain CD8+ TRM cells were long‐lived, slowly proliferating cells able to respond to local challenge infection. Importantly, brain CD8+ TRM cells controlled latent MCMV and their depletion resulted in virus reactivation and enhanced inflammation in brain.