Mechanisms of colchicine effect in the treatment of asbestosis and idiopathic pulmonary fibrosis.

The objective of this study was to evaluate the mechanisms of colchicine action in pulmonary fibrosis. The study included 10 patients with pulmonary fibrosis (idiopathic pulmonary fibrosis 5, asbestosis 4, and scleroderma 1) who had been admitted to Bellevue Hospital Center, a tertiary care public hospital in New York City. We administered colchicine 0.6 mg orally for 12 weeks to patients with pulmonary fibrosis. Symptoms, high resolution CT scans, pulmonary function tests, and bronchoalveolar lavage parameters were compared prior to and after treatment. Results showed declines in dyspnea index, selective improvement in several CT scans, but no statistically significant change in BAL cells, cytokines, fibronectin, or hydroxyproline. However, there was a decline in hydroxyproline in the BAL fluid in 8/10 patients. We concluded that colchicine has a mild antifibrotic effect which may be in inhibiting collagen formation since there was no effect on the inflammation that accompanies fibrosis.

Inhibition of anchorage-independent growth and lung metastasis of A549 lung carcinoma cells by IkappaBbeta.

To evaluate the role of the NF-kappaB signaling pathway in oncogenic transformation, we expressed IkappaBbeta, a specific inhibitor of NF-kappaB, in two human lung adenocarcinoma cell lines, A549 and H441. Expression of IkappaBbeta significantly reduced NF-kappaB activation induced by cotransfection with p65/RelA or TNF-alpha and abrogated the basal NF-kappaB activity in A549 cells. Transfection of IkappaBbeta into A549, H441 and K-ras-transformed NIH3T3 cells suppressed anchorage-independent growth as measured by colony formation in soft agar. Anchorage-independent growth of vector-transfected A549 cells in reduced serum could be enhanced by both EGF and IGF-I. In contrast, only EGF but not IGF-I could induce anchorage-independent growth of IkappaBbeta-expressing A549 cells, suggesting that the IGF-I signaling pathway regulating growth and survival may be blocked by IkappaBbeta. Interestingly, expression of IkappaBbeta suppressed growth of A549 cells in low serum in vitro without affecting in vivo growth subcutaneously in nude mice. However, metastatic growth of IkappaBbeta-expressing A549 cells in the lungs of nude mice was significantly inhibited. These results provide evidence that NFkappaB plays an important role in anchorage-independent growth and metastatic growth of lung carcinoma cells.

Role of c-Jun N-terminal kinase 1 (JNK1) in cell cycle checkpoint activated by the protease inhibitor N-acetyl-leucinyl-leucinyl-norleucinal.

The cysteine protease inhibitor N-acetyl-leucinyl-leucinyl-norleucinal (LLnL) inhibited the growth of the Calu-1 lung carcinoma cells and induced a prolonged cell cycle arrest in the S phase. c-Jun N-terminal kinases (JNKs) participate in cellular responses to mitogenic stimuli, environmental stresses, and apoptotic signals but its role in cell cycle checkpoint control has not been elucidated. In this report, we examined the role of JNK in LLnL-induced S phase checkpoint by overexpression of a dominant-negative mutant of JNK1 (JNK1-APF) in Calu-1 cells. Expression of high levels of JNK1-APF blocked the growth-inhibitory effects of LLnL and abrogated S phase arrest induced by LLnL. These results support the role of JNK in the activation of cell cycle checkpoint induced by LLnL.

Induction of tumor suppression and glandular differentiation of A549 lung carcinoma cells by dominant-negative IGF-I receptor.

Overexpression or activation of insulin-like growth factor I receptor (IGF-IR) has been observed in many human cancers including breast, lung, colon and gastric carcinomas. We demonstrate that inhibition of the endogenous insulin-like growth factor I receptor by stable expression of a dominant-negative IGF-IR represses the transforming activity in vitro and tumorigenicity of human lung carcinoma cells A549 in vivo. The suppression of tumorigenicity in nude mice is correlated with the induction of glandular differentiation. In addition, functional inhibition of the endogenous receptor dramatically increases the sensitivity of A549 cells to a variety of apoptotic signals including UV irradiation and proteasome inhibitors. These effects are due to the formation of a stable heterocomplex of the dominant-negative receptor with the endogenous wild type receptor which reduces the kinase activity of the latter by twofold. Thus, inhibition of the IGF-IR signaling pathway not only suppresses tumorigenicity but also enhances sensitivity to apoptosis-inducing agents. Antagonizing IGF-IR signaling by promoting tumor differentiation and enhancing sensitivity to apoptotic death are potential cancer therapeutic approaches.

Activation of NF-kappaB in Mycobacterium tuberculosis- induced interleukin-2 receptor expression in mononuclear phagocytes.

Soluble interleukin-2 receptor-alpha (IL-2Ralpha) has been reported to be increased in the sera of patients with advanced tuberculosis, and levels decline after therapy in accordance with improvement of radiologic findings. We investigated expression of the IL-2Ralpha in bronchoalveolar lavage (BAL) cells in active pulmonary tuberculosis, and evaluated the mechanism Mycobacterium tuberculosis induces in the IL-2Ralpha using the THP-1 mononuclear phagocyte cell line. We found IL-2Ralpha expression to be increased in BAL cells from involved sites of active pulmonary tuberculosis. Expression of the alpha-chain of IL-2Ralpha on peripheral blood monocytes (PBM) was induced by M. tuberculosis by flow cytometry evaluation. Northern analysis demonstrated increased IL-2Ralpha gene expression after stimulation with M. tuberculosis which was further induced by interferon-gamma (IFN-gamma). The IL-2Ralpha promoter containing the nuclear factor kappa B (NF-kappaB) site was transcriptionally induced by M. tuberculosis and this NF-kappaB site could confer inducibility to a heterologous herpes thymidine kinase (TK) promoter by M. tuberculosis. Electrophoretic mobility shift assays (EMSAs) revealed specific binding of nuclear protein to the NF-kappaB site upon induction with M. tuberculosis. Using antibodies against the p50 and p65 subunits of NF-kappaB in EMSAs, the involvement of both p50 and p65 proteins was further demonstrated. Functional expression of the IL-2Ralpha on mononuclear phagocytes in M. tuberculosis infection may play an important immunomodulatory role in the host response.

Effects of mycobacteria on regulation of apoptosis in mononuclear phagocytes.

Since apoptosis is observed in tuberculous granulomata, we investigated the molecular mechanisms underlying the apoptotic pathway in an in vitro model of mycobacterial infection of mononuclear phagocytes. We postulated that Mycobacterium tuberculosis could trigger the apoptotic pathway in macrophages, resulting in death of the microorganism by modulating the expression of bcl-2, bax, bcl-xL, and bcl-xS. We found that the mRNA of bcl-2, an inhibitor of apoptosis, was downregulated in peripheral blood monocytes (PBM) between 2 and 6 h following infection with M. bovis BCG or induction with heat-killed M. tuberculosis H37Ra. Western analysis showed a downregulation of the Bcl-2 protein, with a half-life of 24 h. At the same time points, there was no change in the expression of Bax or Bcl-xS, inducers of apoptosis, but Bcl-xL, another inhibitor of apoptosis, was minimally upregulated by BCG. To determine if apoptosis could be a mechanism for growth inhibition in vivo, we obtained alveolar macrophages by bronchoalveolar lavage from involved sites in patients with active pulmonary tuberculosis. Using the TUNEL (terminal deoxynucleotidyltransferase mediated nick end labeling) technique, we observed significantly more apoptosis in involved segments of five tuberculosis patients (14.8 +/- 1.9%) than in those of normal controls (<1%, P = 0.02) or in uninvolved segments (4.3 +/- 0.9%, P < 0.05). We conclude that apoptosis of mononuclear phagocytes induced by M. tuberculosis occurs in vivo and that in an in vitro model of mycobacterial infection, apoptosis may be mediated by downregulation of Bcl-2.

Development of a suicide gene as a novel approach to killing Mycobacterium tuberculosis.

The increase in multidrug-resistant tuberculosis and high mortality among those co-infected with HIV-1 necessitates new therapeutic approaches directed at Mycobacterium tuberculosis. We hypothesized that a dominant-negative mutation in the DNA-dependent RNA polymerase gene would inhibit transcription of all genes by blocking access of the wild-type enzyme to promoters. An evolutionarily invariant lysine was substituted with arginine by site-directed mutagenesis in the rpoB gene. The dominant-negative rpoB gene product inhibited a transposon-derived kanamycin-resistance gene in both M. smegmatis and M. tuberculosis H37Rv, leading to growth inhibition of the mycobacteria on solid media containing kanamycin. The dominant-negative mutant rpoB gene is a potential suicide gene especially for the treatment of multidrug-resistant tuberculosis once a delivery strategy is also developed.

GM-CSF gene expression is normal but protein release is absent in a patient with pulmonary alveolar proteinosis.

Pulmonary alveolar proteinosis (PAP) is a rare disease characterized by an excessive accumulation of surfactant lipids and proteins in the alveolar space. In mice with a homozygous deletion of granulocyte macrophage-colony stimulating factor (GM-CSF), their phenotype mimics PAP. To evaluate whether the knockout mouse model mimics human disease, we evaluated GM-CSF expression in alveolar macrophages from a patient with PAP. We performed multiple whole lung lavages on a patient with PAP, and cultured BAL cells in the presence or absence of LPS. In contrast to the GM-CSF knockout mouse, human BAL cells from a patient with PAP expressed mRNA for GM-CSF following LPS stimulation. However, similar to the knockout mouse, GM-CSF protein release from BAL cells was undetectable with or without LPS. BAL cells from normal human controls released GM-CSF in abundance after LPS stimulation. In BAL cells from the patient with PAP, neutralization of interleukin-10 (IL-10) by anti-IL-10 antibody, resulted in enhanced GM-CSF production. Thus, alveolar macrophages from a PAP lung have deficient GM-CSF production analogous to the GM-CSF knockout mice; in contrast, human cells from a PAP lung have an intact GM-CSF gene. This case report illustrates an important difference between the knockout mouse model of PAP and the human disease.

Novel form of p21(WAF1/CIP1/SDI1) protein in phorbol ester-induced G2/M arrest.

Cell cycle progression requires activation of different cyclin-dependent kinases (CDKs) which are positively regulated by cyclins and negatively regulated by CDK inhibitors. Growth inhibition of the Calu-1 lung carcinoma cells induced with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), a potent activator of protein kinase C, is associated with G2/M arrest and induction of expression of a novel, faster-migrating form of p21(WAF1/CIP1/SDI1) (p21) protein, an inhibitor of cyclin-dependent kinases. This faster-migrating p21 protein was also expressed in TPA-treated A549 lung carcinoma cells which also exhibited G2/M arrest but not in TPA-treated U937 leukemia cells, which only expressed a slower-migrating form of p21 protein. However, reverse transcriptase-polymerase chain reaction and Southern analysis demonstrated no evidence of novel splice in TPA-treated Calu-1 cells. On the other hand, immunoblotting analysis demonstrated that the faster-migrating p21 protein could be detected only by peptide antibody directed against the N terminus but not the C terminus, suggestive of truncation of the latter or protein modification that results in the loss of the C-terminal epitope. Correlation of G2/M arrest with expression of the faster-migrating p21 protein suggests that this novel form of p21 protein may be a mediator of G2/M arrest and growth inhibition.

Effect of Mycobacterium tuberculosis and its components on macrophages and the release of matrix metalloproteinases.

BACKGROUND: Pulmonary tuberculosis is associated with caseating necrosis, parenchymal lung destruction, and cavity formation. It was hypothesised that tuberculous lung destruction is mediated, at least in part, by the participation of matrix metalloproteinases released by mononuclear phagocytes. METHODS: Cells of the myelomonocytic leukaemia cell line THP-1 were incubated with lipoarabinomannan (LAM), the major antigenic cell wall component, and with Mycobacterium tuberculosis and analysed by Northern blot analysis. Two patients with active cavitary tuberculosis also underwent bronchoalveolar lavage and the cells were analysed by Northern blotting. RESULTS: Incubation of THP-1 cells with LAM resulted in the stimulated release of matrix metalloproteinase-9 (MMP-9), a 92 kDa gelatinase, by 24 hours in a dose-dependent fashion. In addition, Northern analysis revealed that LAM upregulated the gene for MMP-9 by 24 hours, but not the gene for the 72 kDa gelatinase MMP-2. Heat killed M tuberculosis H37Ra also upregulated the MMP-9 gene. Bronchoalveolar lavage of the two patients with active cavitary tuberculosis showed striking upregulation of the MMP-9 gene compared with a normal control using Northern analysis. LAM also upregulated the type I interstitial collagenase (MMP-1) gene by 24 hours in both THP-1 cells and peripheral blood monocytes. CONCLUSIONS: These data suggest that M tuberculosis and its major cell antigenic component, LAM, stimulate the release of MMP-9 and upregulate the expression of genes for MMP-1 and MMP-9. It is possible that M tuberculosis and its components contribute directly to cavity formation by their ability to stimulate macrophages to release matrix metallo-proteinases that digest collagens I-IV, and indirectly by stimulating the release of the cytokines interleukin 1 beta and tumour necrosis factor alpha that induce fibroblasts to amplify the release of matrix metalloproteinases.

Human host response to Mycobacterium tuberculosis.

Despite the importance of tuberculosis as the leading cause of death due to infectious disease in the world, it has only been recently that an understanding of the human host response in this infection has begun to emerge. The key components of this response are cytokines and components of cellular immunity, predominantly T-lymphocytes and macrophages. Though the relationships among the components of the immune response are complex, it seems likely that in response to mycobacterial infection associated with active disease, cytokines such as TNF-alpha and IL-1 beta are produced; these cytokines serve to recruit more lymphocytes, generally of the T(H) (T helper) phenotype, which then produces substances such as the macrophage activating factor interferon-gamma. Macrophages activated by IFN-gamma ar thus stimulating to enhance intracellular killing of mycobacteria. The role of other cytokines, such as IL-6 and IL-8, both of which are induced by M. tuberculosis or its cell was components, is less clear. Further elucidation of the human host response to tuberculosis should help in the development of new vaccines and treatment strategies.

Altered expression of protein kinase C, lck, and CD45 in a 12-O-tetradecanoylphorbol-13-acetate-dependent leukemic T-cell variant that expresses a high level of interleukin-2 receptor.

The compound 12-O-tetradecanoylphorbol-13-acetate (TPA) is extremely toxic to the P13 subclone of the Jurkat human T-cell leukemia line. By selecting for growth in the presence of TPA, we have isolated two TPA-resistant variants of these cells, P13-50 and P13-5/A8. Studies of protein kinase C (PKC) enzyme activity, immunoblot analyses, and assays for PKC mRNAs indicate that both of these variants express lower levels of PKC than do the parental P13 cells. We suggest that this protects them from the toxic effects of TPA. The P13-5/A8 cells are of particular interest because not only are they resistant to TPA toxicity but they actually require TPA for optimal growth. These cells have a more profound decrease in PKC expression that do P13-50 cells. In addition, P13-5/A8 cells display very little, if any, surface expression of CD45, a receptor-linked tyrosine protein phosphatase, and lck, a lymphocyte-specific tyrosine kinase. On the other hand, they express a very high level of interleukin-2 receptor. A model is proposed that suggests that these cells are dependent on TPA because they have defects in both the PKC and tyrosine kinase signal transduction pathways, and that TPA compensates for these defects by providing a strong stimulus to the residual level of PKC. This variant may be useful for studying the interactions between tyrosine kinase and PKC pathways in controlling the various functions of T lymphocytes.

Overexpression of protein kinase C in HT29 colon cancer cells causes growth inhibition and tumor suppression.

By using a retrovirus-derived vector system, we generated derivatives of the human colon cancer cell line HT29 that stably overexpress a full-length cDNA encoding the beta 1 isoform of rat protein kinase C (PKC). Two of these cell lines, PKC6 and PKC7, displayed an 11- to 15-fold increase in PKC activity when compared with the C1 control cell line that carries the vector lacking the PKC cDNA insert. Both of the overexpresser cell lines exhibited striking alterations in morphology when exposed to the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Following exposure to TPA, PKC6 and PKC7 cells displayed increased doubling time, decreased saturation density, and loss of anchorage-independent growth in soft agar; but these effects were not seen with the C1 cells. Also, in contrast to the control cells, the PKC-overproducing cells failed to display evidence of differentiation, as measured by alkaline phosphatase activity, when exposed to sodium butyrate. In addition, the PKC-overexpresser cells displayed decreased tumorigenicity in nude mice, even in the absence of treatment with TPA. These results provide the first direct evidence that PKC can inhibit tumor cell growth. Thus, in some tumors, PKC might act as a growth-suppressor gene.