Changes in gene expression in the lungs of Mg-deficient mice are related to an inflammatory process

It has been well documented that experimental hypomagnesemia in rodents evokes, as an early consequence, an inflammatory response. This also leads to the activation of cells producing reactive species of oxygen and, as a result, to the oxidative damage of tissues. Several studies have shown that lungs might be a specific target of Mg deficiency. Here, we report that 3 weeks of Mg deficiency in mice resulted in inflammatory processes in the lungs, including interstitial and perivascular pneumonia, manifested by the infiltration of leukocytes, plasmocytes and histiocytes, as well as the phenomenon of disseminated intravascular coagulation (DIC). These phenomena were accompanied by changes in gene expression assessed by cDNA array. In this study we identified 26 genes significantly changed by Mg deficiency, mostly involved in the anti-oxidative response, regulation of cell cycle and growth, apoptosis as well as cell-cell and cell-matrix interactions. We conclude that these changes are related to the phenomena of inflammatory and oxidative processes and consecutive remodeling occurring in the tissues as a result of Mg deficiency. This may have implications for at least several lung pathologies, including allergies, asthma, SIDS (Sudden Infant Death Syndrome) or facilitate formation of lung metastases.

Antiapoptotic action of prolactin is associated with up-regulation of Bcl-2 and down-regulation of Bax in HC11 mouse mammary epithelial cells

The effect of prolactin on apoptosis and the expression of bcl-2 and bax in HC11 mouse mammary epithelial cells were investigated. Flow cytometric analysis of Bcl-2 level (FITC-conjugated monoclonal anti-Bcl-2 antibody and FITC-conjugated monoclonal anti-IgG1 antibody as a negative control), number of apoptotic cells and cell cycle phases (DNA stained with DAPI) was performed. Bax transcript was measured using the RT-PCR method with GAPDH serving as a reference gene. Administration of prolactin (5 microg/ml) in the presence of insulin stimulated differentiation of mammary epithelial cells, which manifested in stopping cells at G0/G1 phase, cell swelling and increase of cell number with enhanced protein content. Moreover, prolactin highly significantly reduced the extent of apoptosis of HC11 cells during 48 h of incubation. Nevertheless, the apoptotic cell number rose with increased time length of cell culture, probably due to the resulting high cell density and EGF withdrawal from t he incubation medium. The antiapoptotic effect of prolactin was associated with up-regulation of bcl-2 expression, shown as an increase in cell numbers expressing this protooncogene and elevated Bcl-2 content in these cells. A negative relationship (r=-0.87, p< or =0.001) between the number of apoptotic cells and those expressing bcl-2 was also found. Prolactin administration lowered Bax transcript by 68.8% and 70.7% after 3 and 6h, respectively. In conclusion, the results presented indicate that stimulation of bcl-2 expression with simultaneous suppression of bax may be key events in the mechanism of antiapoptotic action of prolactin in HC11 mammary epithelial cells.

Increase in complement component C3 is an early response to experimental magnesium deficiency in rats

The importance of the inflammatory process in the pathology of experimental Mg-deficiency has been reconsidered but the sequence of events leading to inflammatory response remains unclear. In this study, the effect of Mg-deficiency on complement system by measuring total C3 concentration, mRNA abundance for rat pre-pro complement C3 in liver by RT-PCR, complement haemolytic activity and C3 activation by Western Blot was studied. Weaning male Wistar rats were fed either Mg-deficient or control experimental diets for 2 or 8 days. At 8 days, a characteristic inflammatory response of Mg-deficiency including hyperaemia, leukocytosis and enlarged spleen was accompanied by an increase in the total C3 quantity in plasma. Moreover, at 8 days, RT-PCR analysis indicated higher level of mRNA rat pre-pro complement C3 in liver from Mg-deficient rats compared to control rats. Even if the inflammatory syndrome was not observed in rats after 2 days, total plasma C3 was shown to be significantly increased as compared to total plasma C3 level in control rats. Because of the high variability of complement haemolytic activity values in Wistar rats, weaning male Sprague-Dawley rats were used in a second experiment. At 8 days, the inflammatory response of Sprague-Dawley rats was accompanied by an increase in total C3 quantity and by a higher haemolytic activity. The Western Blot technique failed to display distinct bands resulting from C3 cleavage in plasma from Mg-deficient rats. Since, the complement C3 is a positive acute phase reactant, the elevation of C3 indicates that the modification of inflammatory response is an early event of Mg-deficiency. However, complement activation does not appear to be involved in the acute phase of the deficiency.

Morphological and immune response alterations in the intestinal mucosa of the mouse after short periods on a low-magnesium diet

The importance of Mg for the immune function is well recognized; however, there is no information available about the effect of Mg intake on the modulation of local immune response in the intestine. Thus, in the present study the hypothesis that short periods of Mg deprivation can affect intestinal mucosa and local immune response was tested. For this purpose, OF1 female mice were fed a semipurified diet (1000 mg Mg/kg diet). For 3 d before immunization and 1 d after, half of the animals were fed a Mg-deficient diet (30 mg Mg/kg diet), three immunizations per os were performed every 3 weeks with Escherichia coli producing the CS31A capsule-like protein (1010 or bacteria per animal). Mice were killed 10 d after the last immunization. The level of specific anti CS31A immunoglobulin (Ig) G and IgA in the serum and secretory IgA in the intestinal secretions and faeces were measured by ELISA. The results indicated that administration of a high dose of immunogen with a low-Mg diet led to lower specific IgA levels in the intestinal mucus and serum. Administration of a low dose of immunogen with a low-Mg diet led to lower IgA and IgG levels in the serum and secretory IgA coproantibodies. To assess alterations of intestinal mucosa caused by a low-Mg diet for a short period, histological and scanning electron microscopy analyses were performed on samples from mice (not submitted to the vaccination protocol) after 3 d on the Mg-deficient diet. These analyses showed several alterations, suggesting perturbations in the growth of the intestinal mucosa. These changes were accompanied by modifications in the expression of several genes involved in cell growth and stress response. From this present work, it may be concluded that short periods of Mg deprivation can affect the intestinal mucosa and local immune response of the intestine.

Stress protein expression cDNA array study supports activation of neutrophils during acute magnesium deficiency in rats

Recent studies underline the importance of the immunoinflammatory processes in the pathology of acute magnesium (Mg)-deficiency. The aim of this study was to assess the effect of acute experimental Mg-deficiency in the rat on neutrophil activity. Weaning male Wistar rats were fed either a Mg-deficient or a control diet for 8 days. In this experiment, we measured neutrophil respiratory burst by chemiluminescence; then, to examine the molecular events associated with acute Mg-deficiency, we applied cDNA array technology to define the transcription response in neutrophils of Mg-deficient rats in comparison with controls. In Mg-deficient rats, the characteristic inflammatory response was accompanied by a marked increase in the number of neutrophils. Moreover, as shown by chemiluminescence studies, basal neutrophil activity from Mg-deficient rats was significantly elevated when compared to neutrophils from control rats. Moreover, the chemiluminescence of neutrophils from Mg-deficient rats was significantly higher than that of control rats following phorbol myristate acetate or opsonized zymosan activation. Using cDNA array which includes 207 known rat genes of stress proteins, 102 genes were found to be expressed in neutrophils. Among expressed genes, 78 per cent of genes were found to be expressed more than twofold in neutrophils from Mg-deficient rats compared to control rats. Acute Mg-deficiency was characterized by an induction of genes encoding for proteins involved in apoptosis, heat shock proteins, protein belonging to the cytoskeleton, proteins implicated as stress response regulators and effectors and enzyme implicated in thromboxane synthesis. Then, this experimental strategy allowed to identify a series of genes implicated in the immunoinflammatory process of Mg-deficiency.

Inhibition of ornithine decarboxylase by alpha-difluoromethylornithine induces apoptosis of HC11 mouse mammary epithelial cells

The effect of a-difluoromethylornithine (DFMO) on the apoptosis of HC11 mouse mammary epithelial cells was investigated. The involvement of reactive oxygen species (ROS) and Bcl-2 protein in the mechanism of apoptosis induced by ornithine decarboxylase (ODC) inhibition was also assessed. DFMO (0.1, 1 and 5mM) induced apoptosis of HC11 cells in dose- and time-dependent manner. Apoptosis manifests itself with morphological features like: cell shrinkage, condensation of chromatin, pyknosis and fragmentation of nucleus, followed by secondary necrosis (putrosis). The decrease in the nuclear DNA contents appearing as the hypodiploidal peak sub-G1 in the DNA histogram was not dependent on the presence of prolactin (5 microg/ml) in DFMO-treated cultures. Apoptosis induced by ODC inhibition was associated with a rapid increase in ROS concentration in HC11 cells observed within 1 h after DFMO treatment. The down-regulation of Bcl-2 as a decrease in cell number expressing bcl-2 and a lowered Bcl-2 protein content in cells expressing this protooncogene was also noted. The administration of putrescine (50 microM) lowered the number of early-apoptotic, late-apoptotic and necrotic cells. Moreover, it increased the number of cells expressing bcl-2. In conclusion, the disturbance of cellular polyamine homeostasis by inhibition of their synthesis enhances mammary epithelial cell susceptibility to apoptosis. It may occur in the mammary gland at the end of lactation, when the depletion of circulating lactogenic hormones and activation of intra-mammary apoptogenic factors expression take place.

Induction of apoptosis and NF-kappaB by quercetin in growing murine L1210 lymphocytic leukaemic cells potentiated by TNF-alpha

Polyphenol quercetin induced apoptosis in proliferating murine L1210 lymphocytic cells. DNA damage, as well as apoptosis and withdrawal from the cell cycle were transient. The above mentioned death promoting activity of quercetin was enhanced by physiological concentrations of TNF-alpha. At the same time, indices of cell viability dropped. However, the extent and tendency of the initially enhanced cell mortality steadily diminished throughout the experiment. After 12 h the G2/M phase reappeared. After 24 h all indices almost returned to control levels indicating either the selection of subpopulation of unaffected leukaemic cells or cells developing resistance to the treatment. A DNA ladder of oligonucleosomes was observed for apoptogenic treatments. We conclude that quercetin unmasked cell death, promoting the activity of TNF-alpha. However, after 12 and 24 h of exposure, surviving cells could complete the cell cycle and finally recover. At the same time, increased NF-kappaB activation was demonstrated by immunoblotting of the immunoreactive RelA/p65 subunit in nuclear extracts. Exposure to TNF-alpha or quercetin was crucial for increased activity of NF-kappaB, which may implicate an increasing resistance to their cytotoxicity.

Expression and subcellular redistribution of Bax during TGF-beta1-induced programmed cell death of HC11 mouse mammary epithelial cells

The effect of TGF-beta1, an auto/paracrine antiproliferative and apoptogenic factor on Bax transcript level (RT-PCR), subcellular distribution of Bax protein (immunoelectron microscopy), Bcl-2 protein level and apoptotic cell number (flow cytometry with FITC-conjugated monoclonal anti-Bcl-2 antibody and DNA stained with DAPI) in HC11 mouse mammary epithelial cells was examined. TGF-beta1 increased Bax transcript level (evaluated by Bax mRNA/GAPDH mRNA ratio) and stimulated Bax protein movement from cytosol to organellar membranes, mainly mitochondrial, during 60 min. The new observation is the presence of Bax on channel membranes of Golgi apparatus and translocation of Bax from cytosol to the fibrous nucleoplasm via nuclear envelope pores (especially after 120 min. of cell exposure to TGF-beta1). Prolactin protected HC11 cells against TGF-beta1-induced PCD, which could occur at two levels: 1) TGF-beta1 expression, through the decrease of TGF-beta1 transcript content, and 2) Bax/Bcl-2 checkpoint, through down-regulation of Bax and up-regulation of Bcl-2. In conclusion, Bax and Bcl-2 proteins are implicated in the mechanism of TGF-beta1-induced PCD and antiapoptotic action of prolactin in HC11 mouse mammary epithelial cells. The activation of transcription and redistribution of Bax from cytosol to organellar membranes and nucleus constitute the early events in the cellular response to TGF-beta1.

Expression of bcl-2 and bax in TGF-beta 1-induced apoptosis of L1210 leukemic cells

TGF-beta1 is a multifunctional regulatory peptide (25 kDa) inducing growth arrest and apoptosis in many normal and neoplastic cells. In the present study, the involvement of proapoptotic (bax) and antiapoptotic (bcl-2) genes in the molecular mechanism of TGF-beta1-induced apoptosis of L1210 leukemic cells was investigated. Bax transcript was measured using the RT-PCR method with GAPDH as a "housekeeping gene" control, whereas Bcl-2 protein was determined using flow cytometry (FITC-conjugated monoclonal anti-Bcl-2 antibody and FITC-conjugated mouse anti-IgG1 antibody as a negative control). Apoptosis was evaluated using fluorescence microscopy and flow cytometry after cell staining with DAPI and sulforhodamine or propidium iodide and Hoechst 33342. ROS generation was assessed by flow cytometry using the oxidation-sensitive fluorescent marker C-DCDHF-DA. The response of L1210 leukemic cells to TGF-beta1 was two-directional: 1) partial arrest of the cell cycle at G1-S transition, and 2) induction of apoptotic cell death. TGF-beta1 increased the number of leukemic cells with typical morphological features of apoptosis: cell shrinkage, condensation of chromatin, pyknosis and fragmentation of nuclei, followed by secondary necrosis. DNA cleavage led to a decrease of the nuclear DNA content and the appearance of a hypodiploid peak sub-G1 in the DNA histogram. The extraction of low-molecular weight DNA fragments from apoptotic cells showed that TGF-beta1-induced apoptosis concerned first of all the cells from G1 phase. Two phases of intracellular ROS generation in TGF-beta1-treated cultures were observed: the first (rapid, 60 min after TGF-beta1 administration), and the second (slow, occurring between 24 and 48h of experiment, respectively). The increase of apoptotic cell number in TGF-beta1-treated cultures (2% FCS/RPMI 1640) was associated with the decrease of cell number expressing bcl-2, and with a significant drop of Bcl-2 level in the remaining cells after 24 h. The dose-dependent relationship between TGF-beta1 concentration and Bcl-2 level was nonlinear and described by power series regression. The lowest Bcl-2 level was noted at 1 ng/ml of TGF-beta1 concentration. The increase of Bax mRNA:GAPDH mRNA ratio was observed 3h after TGF-beta1 (1 ng/ml) administration to both the maintenance (2% FCS/RPMI) and growth promoting (10% FCS/RPMI) medium. Regardless of TGF-beta1 treatment, the quantity of Bax transcript was dependent on FCS concentration, being higher in the growth promoting medium. The results of this study indicate that bax may function as a primary response gene and together with lowered Bcl-2 level may determine the induction of apoptotic process in L1210 leukemic cells exposed to TGF-beta1.

Apoptosis and Bcl-2 protein changes in L1210 leukaemic cells exposed to oxidative stress

The aim of this study was to explore the dose- and time-dependent effects of hydrophilic peroxyl radical initiator 2,2'azobis(2amidinopropane)dihydrochloride (AAPH) on apoptosis, and on expression of Bcl-2 in L1210 leukaemic cells. We observed a progressive increase of intracellular concentration of oxygen free radicals (OFR), manifested by the rise of 6-carboxy-2', 7'-dichlorodihydrofluorescein diacetate, di(acetoxymethyl ester) oxidation, during 24 h of cells exposure to AAPH. Oxidative stress was associated with peroxidation of cellular lipids, which was demonstrated by the measurement of thiobarbituric acid-reactive substances and conjugated dienes. Analysis of cell viability by the use of trypan blue exclusion method revealed that AAPH reduced the ability of L1210 cells to multiply or survive. AAPH increased the number of leukaemic cells with typical features of apoptosis like condensation of chromatin, pyknosis and fragmentation of nucleus, followed by secondary necrosis. A characteristic internucleosomal DNA cleavage, visualized as a DNA 'ladder' consisting of fragments that are multiples of 180-200 bp was also observed. The intensity of apoptosis was dependent on AAPH concentration, time of cell exposure and the availability of growth factors and nutrients in extracellular environment (FCS concentration). The novel observation is the increase of Bcl-2 level in L1210 leukaemic cells surviving an oxidative stress. The level of Bcl-2 protein significantly rose with increasing AAPH concentration, and time of cell exposure to this oxidant. This phenomenon could be the result of: (1) negative selection of cells with the lowest expression of bcl-2, being more susceptible to oxidative stress and (2) increased synthesis and/or decreased degradation of Bcl-2 protein as an adaptation to continuous OFR loading. In contrast to growth-promoting medium (10% FCS/RPMI), the maintenance medium (2% FCS/RPMI) did not cover cell requirements for progressive Bcl-2 increase at the highest AAPH concentration (2 mM) applied in this study. Several observations indicate that the increased Bcl-2 level in surviving L1210 leukaemic cells exposed to oxidative stress is a symptom of their natural defence against cellular lipids peroxidation and apoptosis.