Analysis of DNA synthesis in herpes simplex virus infected cells by dual parameter flow cytometry

Transgenic extracellular superoxide dismutase protects postnatal alveolar epithelial proliferation and development during hyperoxia

Transgenic (TG) human (h) extracellular superoxide dismutase (EC-SOD) targeted to type II cells protects postnatal newborn mouse lung development against hyperoxia by unknown mechanisms. Because alveolar development depends on timely proliferation of type II epithelium and differentiation to type I epithelium, we measured proliferation in bronchiolar and alveolar (surfactant protein C-positive) epithelium in air and 95% O2-exposed wild-type (WT) and TG hEC-SOD newborn mice at postnatal days 3, 5, and 7 (P3-P7), traversing the transition from saccular to alveolar stages. We found that TG hEC-SOD ameliorated the 95% O2-impaired bromodeoxyuridine uptake in alveolar and bronchiolar epithelium at P3, but not at P5 and P7, when overall epithelial proliferation rates were lower in air-exposed WT mice. Mouse EC-, CuZn-, and Mn-SOD expression were unaffected by hyperoxia or genotype. TG mice had less DNA damage than 95% O2-exposed WT mice at P3, measured by TdT-mediated dUTP nick end labeling (P < 0.05). Hyperoxia induced cell-cycle inhibitory protein p21cip/waf mRNA at P3, WT > TG, P = 0.06. 95% O2 impaired apical expression of type I cell alpha protein (T1alpha) in WT but not in TG mice at P3 and increased T1alpha in WT and TG mice at P7. Reducing the 95% O2-induced impairment of epithelial proliferation at a critical window of lung development was associated with protection against DNA damage and preservation of apical T1alpha expression at P3.

The role of p53 in bleomycin-induced DNA damage in the lung. A comparative study with the small intestine

To elucidate the role of p53 and apoptosis in the pathogenesis of lung injury, we examined histological changes, expressions of p53 and p21waf1/cip1 (p21), apoptosis, DNA double strand breaks, cell kinetics, and DNA synthesis in C57/BL6 mice (p53+/+) and mice deficient for p53 (p53-/-) at 2 hours to 7 days after a single intravenous administration of bleomycin. We also compared these parameters between the lung cells and small intestinal epithelial cells to explore potential differences in their response to DNA damage. Bleomycin induced p21 expression in a p53-dependent manner in p53+/+ mice but neither p53 nor p21 expression in p53-/- mice. In the lung of both groups of mice, focal inflammation followed by fibrosis was observed, but there was no evidence of apoptosis. Cells with DNA breaks and those undergoing DNA synthesis were unequivocally increased, but the cycling cell fraction remained unchanged, suggesting that the DNA synthesis detected in the lung reflected unscheduled DNA synthesis for repair of damaged DNA. DNA breaks and unscheduled DNA synthesis were prolonged in p53-/- mice compared to p53+/+ mice. By contrast, in the small intestine, marked cell cycle arrest and extensive apoptosis were evoked in the cycling crypt cells of both groups of mice, but these changes were milder and DNA breaks remained detectable for a longer time in p53-/- mice than in p53+/+ mice. Among the resting enterocytes in the villi, apoptosis was observed almost equally in both groups, but repair of DNA breaks was significantly delayed in the p53-/- mice. These observations imply that apoptosis is mediated largely by the p53-dependent pathway in the crypts but exclusively by the p53-independent pathway in the villi, that this pathway is particularly important in DNA repair in the villi, and that despite this difference in the significance of apoptosis, p53 plays an important role in DNA repair in both the crypts and villi. Our results suggest that the lung cells and small intestinal cells respond to the bleomycin treatment in different ways in terms of the induction of apoptosis and that p53 carries out an essential role in the early response to and repair of DNA damage by a non-apoptotic mechanism which appears to be crucial in the noncycling lung cells and enterocytes. Importantly, the p53-p21 pathway and apoptosis are unlikely to be essential for bleomycin-induced tissue injury in the lung.

Bromodeoxyuridine: a diagnostic tool in biology and medicine, Part III. Proliferation in normal, injured and diseased tissue, growth factors, differentiation, DNA replication sites and in situ hybridization

This paper is a continuation of parts I (history, methods and cell kinetics) and II (clinical applications and carcinogenesis) published previously (Dolbeare, 1995 Histochem. J. 27, 339, 923). Incorporation of bromodeoxyuridine (BrdUrd) into DNA is used to measure proliferation in normal, diseased and injured tissue and to follow the effect of growth factors. Immunochemical detection of BrdUrd can be used to determine proliferative characteristics of differentiating tissues and to obtain birth dates for actual differentiation events. Studies are also described in which BrdUrd is used to follow the order of DNA replication in specific chromosomes, DNA replication sites in the nucleus and to monitor DNA repair. BrdUrd incorporation has been used as a tool for in situ hybridization experiments.

Herpes simplex virus induces unscheduled DNA synthesis in virus-infected cervical cancer cell lines

We evaluated herpes-simplex-virus-type-2(HSV2)-induced unscheduled DNA synthesis in virus-infected cervical cancer (HeLa, CaSki, C-33A, and SiHa) cells. HSV2 replication was approximately 100-fold more efficient in the HeLa cells than in less susceptible C-33A and SiHa cells. In dual parameter flow cytometric analysis of bromodeoxyuridine (BrdU) incorporation, HSV2-infected HeLa cells showed a rapid increase in the proportions of DNA-synthesizing G1- and S-phase cells, whereas in C-33A and SiHa cells, the proportions of DNA-synthesizing G1- and early S-phase cells were increased late in the infection. Blocking of HSV2 replication by phosphonoformate inhibited virus-induced changes in HeLa cells, but not in C-33A and SiHa cells. Anti-BrdU antibodies exhibited a coarse globular nuclear staining pattern in the C-33A cells, while the other cells showed speckled and/or fine globular nuclear fluorescence. Anti-ICP8 (HSV-specified major DNA-binding protein) antibodies revealed that, in C-33A cells, ICP8 remained in the cytoplasm, whereas in the other cells, speckled or globular nuclear fluorescence was found. Our results showed that HSV2 induced the unscheduled synthesis of cellular DNA, which was host-cell-dependent, and in virus infected C-33A cells, it may be attributable to both viral and cellular proteins.

Receptor-initiated activation of cells and their oncogenes by herpes-family viruses

The interaction of human cytomegalovirus (HCMV) with the cell membrane has been shown to initiate a cascade of physiologic and biochemical responses that result in the transcriptional activation of specific cellular proto-oncogenes. The cell-activation responses initiated by the virus membrane interaction appear to be important for efficient HCMV replication, as pharmacologic inhibition of cell activation responses significantly reduces the expression of immediate early viral genes and the production of infectious progeny virus. Cellular receptor proteins for other viruses have been shown to be molecules with physiologic activities. Binding of virus to these receptors may trigger the cell to initiate changes that are important for efficient viral replication. These viruses may also trigger inappropriate physiologic responses in the absence of viral replication, thereby causing more covert manifestations of viral pathology.