Effects of benzoxazinorifamycin KRM-1648 on cytokine production at sites of Mycobacterium avium complex infection induced in mice

TGF-β-mediated sustained ERK1/2 activity promotes the inhibition of intracellular growth of Mycobacterium avium in epithelioid cells surrogates

Transforming growth factor beta (TGF-β) has been implicated in the pathogenesis of several diseases including infection with intracellular pathogens such as the Mycobacterium avium complex. Infection of macrophages with M. avium induces TGF-β production and neutralization of this cytokine has been associated with decreased intracellular bacterial growth. We have previously demonstrated that epithelioid cell surrogates (ECs) derived from primary murine peritoneal macrophages through a process of differentiation induced by IL-4 overlap several features of epithelioid cells found in granulomas. In contrast to undifferentiated macrophages, ECs produce larger amounts of TGF-β and inhibit the intracellular growth of M. avium. Here we asked whether the levels of TGF-β produced by ECs are sufficient to induce a self-sustaining autocrine TGF-β signaling controlling mycobacterial replication in infected-cells. We showed that while exogenous addition of increased concentration of TGF-β to infected-macrophages counteracted M. avium replication, pharmacological blockage of TGF-β receptor kinase activity with SB-431542 augmented bacterial load in infected-ECs. Moreover, the levels of TGF-β produced by ECs correlated with high and sustained levels of ERK1/2 activity. Inhibition of ERK1/2 activity with U0126 increased M. avium replication in infected-cells, suggesting that modulation of intracellular bacterial growth is dependent on the activation of ERK1/2. Interestingly, blockage of TGF-β receptor kinase activity with SB-431542 in infected-ECs inhibited ERK1/2 activity, enhanced intracellular M. avium burden and these effects were followed by a severe decrease in TGF-β production. In summary, our findings indicate that the amplitude of TGF-β signaling coordinates the strength and duration of ERK1/2 activity that is determinant for the control of intracellular mycobacterial growth.

Development of new antituberculous drugs based on bacterial virulence factors interfering with host cytokine networks

The worldwide increase in the prevalence of tuberculosis (TB), especially multidrug-resistant TB and extensively drug-resistant TB, is an important global health concern, and new effective drugs are urgently needed. Information on the genome of Mycobacterium tuberculosis (MTB) and various mycobacterial virulence genes is leading to the identification of genes that code for new drug targets. Mycobacterium tuberculosis (MTB) is resistant to the antimicrobial mechanisms of host macrophages and can survive and replicate in macrophages for long periods, resulting in a persistent infection. Mycobacterial virulence factors suppress macrophage bactericidal functions partly via their downregulatory effects on the host antimicrobial cytokine networks, consisting of proinflammatory, immunopotentiating, and Th1-inducing cytokines. Thus, for the development of unique drugs that exhibit antimycobacterial action through novel mechanisms, it is reasonable to search for targets among bacterial genes encoding virulence factors which interfere with the host cytokine responses protective to mycobacterial pathogens. In this review, we discuss the profiles of cytokine networks related to host resistance to mycobacteria, including the mechanisms of downregulation of host antimycobacterial immunity due to immunosuppressive cytokines, which are occasionally induced in the advanced stages of TB. We also highlight the development of antituberculous drugs based on bacterial virulence factors interfering with the host antimycobacterial cytokine network.

TGF-beta plasma levels in chromoblastomycosis patients during itraconazole treatment

BACKGROUND

Chromoblastomycosis (CBM) is a dermal mycosis. The disease evolves to a chronic state, presenting a suppurative granulomatous dermatitis, combined with variable dermal fibrosis. Pathogenesis of the inflammation and tissue repair in CBM are poorly understood.

AIM

To quantify Transforming Growth Factor-beta (TGF-beta) plasma levels of CBM patients during itraconazole (ITZ) treatment.

METHODS

Blood plasma of 12 CBM patients was subjected to TGF-beta titration with ELISA at 0, 3, 6 and 12months of 200mg per day of ITZ therapy, and correlated with the clinical aspects. Plasma of 12 healthy individuals were used for control.

RESULTS

CBM patients present high plasma levels of TGF-beta (7.016+/-1988pg/ml), decreasing after 03months (4.625+/-645pg/ml) of ITZ treatment, which correlates with a rapid clinical improvement. However, after 6 (6.566+/-777pg/ml) and 12months (6.908+/-776) of treatment, TGF-beta levels increase to almost the same levels observed before treatment, which is related to a slow clinical improvement, fungal persistence on the lesion, and fibrotic scars.

CONCLUSION

TGF-beta plasma levels are high in CBM patients. Fungal destruction by ITZ correlates with TGF-beta downregulation, but tissue remodeling and fungal persistence probably raises its levels again, interfering with cellular immune responses.

Rifamycins--obstacles and opportunities

With nearly one-third of the global population infected by Mycobacterium tuberculosis, TB remains a major cause of death (1.7 million in 2006). TB is particularly severe in parts of Asia and Africa where it is often present in AIDS patients. Difficulties in treatment are exacerbated by the 6-9 month treatment times and numerous side effects. There is significant concern about the multi-drug-resistant (MDR) strains of TB (0.5 million MDR-TB cases worldwide in 2006). The rifamycins, long considered a mainstay of TB treatment, were a tremendous breakthrough when they were developed in the 1960's. While the rifamycins display many admirable qualities, they still have a number of shortfalls including: rapid selection of resistant mutants, hepatotoxicity, a flu-like syndrome (especially at higher doses), potent induction of cytochromes P450 (CYP) and inhibition of hepatic transporters. This review of the state-of-the-art regarding rifamycins suggests that it is quite possible to devise improved rifamycin analogs. Studies showing the potential of shortening the duration of treatment if higher doses could be tolerated, also suggest that more potent (or less toxic) rifamycin analogs might accomplish the same end. The improved activity against rifampin-resistant strains by some analogs promises that further work in this area, especially if the information from co-crystal structures with RNA polymerase is applied, should lead to even better analogs. The extensive drug-drug interactions seen with rifampin have already been somewhat ameliorated with rifabutin and rifalazil, and the use of a CYP-induction screening assay should serve to efficiently identify even better analogs. The toxicity due to the flu-like syndrome is an issue that needs effective resolution, particularly for analogs in the rifalazil class. It would be of interest to profile rifalazil and analogs in relation to rifampin, rifapentine, and rifabutin in a variety of screens, particularly those that might relate to hypersensitivity or immunomodulatory processes.

Roles of tumour necrosis factor-alpha (TNF-alpha), transforming growth factor-beta (TGF-beta), and IL-10 in the modulation of intercellular adhesion molecule-1 (ICAM-1) expression by macrophages during mycobacterial infection

Profiles of ICAM-1 expression on cultured murine peritoneal macrophages infected with Mycobacterium avium complex (MAC) were examined, with special reference to modulating roles of TNF-alpha, TGF-beta, and IL-10. When macrophages were infected with MAC, ICAM-1 expression, measured by microscopic counting of ICAM-1+ macrophages stained with anti-ICAM-1 antibody, ELISA, and flow cytometric analysis, was rapidly increased, peaking at day 3 (early-phase up-regulation) due to endogenous TNF-alpha, and thereafter gradually declined to the normal level within 1 week or more (late-phase down-regulation). The late-phase ICAM-1 down-regulation was also seen in macrophages phagocytosing heat-killed MAC and those stimulated with lipopolysaccharide but not in macrophages phagocytosing latex beads. ICAM-1 mRNA expression was augmented markedly at day 1 after MAC infection and thereafter decreased. While TNF-alpha and IL-10 production by MAC-infected macrophages was observed during the first 3 days, TGF-beta production was initiated from day 3 and continued until day 14. Exogenously added TGF-beta strongly inhibited the early-phase increase in ICAM-1 expression by infected macrophages, and the blockade of endogenous TGF-beta with anti-TGF-beta antibody markedly inhibited late-phase ICAM-1 down-regulation. Moderate blocking effect was also observed for anti-IL-10 antibody. On the other hand, late-phase ICAM-1 down-regulation was not prevented by the addition of exogenous TNF-alpha. Therefore, TGF-beta and IL-10, especially the former, appear to play active roles in the late-phase down-regulation of ICAM-1 in MAC-infected macrophages during long-term cultivation.

Effects of secretory leucocyte protease inhibitor on the production of the anti-inflammatory cytokines, IL-10 and transforming growth factor-beta (TGF-beta), by lipopolysaccharide-stimulated macrophages

We studied the effects of secretory leucocyte protease inhibitor (SLPI) on the production of the anti-inflammatory cytokines, IL-10 and TGF-beta, by lipopolysaccharide (LPS)-stimulated macrophages, using half-sized SLPI (1/2 SLPI) containing the C-terminal domain (Arg58-Ala107). ELISA testing of macrophage culture fluids showed a temporary production of IL-10 by the macrophages in the early phase (24 h) after LPS stimulation at low (1 ng/ml) or high (10 microg/ml) concentrations. On the other hand, TGF-beta production was initiated after day 3 and progressively increased. 1/2 SLPI significantly increased IL-10 and TGF-beta production by macrophages in response to a low dose as well as a high dose of LPS. Reverse transcription-polymerase chain reaction analysis showed that 1/2 SLPI caused a significant increase in the expression of both IL-10 and TGF-beta mRNAs by LPS-stimulated macrophages. Thus, although the profile of macrophage TGF-beta production by LPS-stimulated macrophages is markedly different from that of their IL-10 production, SLPI causes an up-regulation of the production of these anti-inflammatory cytokines by LPS-stimulated macrophages.

Prospects for development of new antimycobacterial drugs

In this article, I have thoroughly reviewed the status of development of new antimycobacterial drugs, particularly fluoroquinolones (ciprofloxacin, ofloxacin, sparfloxacin, levofloxacin, gatifloxacin, sitafloxacin, and moxifloxacin), new macrolides (clarithromycin, azithromycin, and roxithromycin), rifamycin derivatives (rifabutin, rifapentine, and KRM-1648), and others. The main purpose of this review was to describe the in-vitro and in-vivo activities of these drugs against Mycobacterium tuberculosis and Mycobacterium avium complex. In addition, the therapeutic efficacy of these drugs in the clinical treatment of mycobacterial infections has also been briefly mentioned.

The modulating effects of proinflammatory cytokines interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha), and immunoregulating cytokines IL-10 and transforming growth factor-beta (TGF-beta), on anti-microbial activity of murine peritoneal macrophages against Mycobacterium avium-intracellulare complex

We assessed the roles of proinflammatory cytokines IFN-gamma and TNF-alpha, and immunoregulatory cytokines IL-10 and TGF-beta in the modulation of the anti-microbial activity of murine peritoneal macrophages against Mycobacterium avium-intracellulare complex (MAIC). First, both IFN-gamma and TNF-alpha significantly reduced the bacterial growth in macrophages, indicating that these cytokines participate in up-regulation of macrophage anti-MAIC function. Second, although MAIC-infected macrophages produced substantial amounts of IL-10 and TGF-beta, neutralization of endogenous IL-10 and TGF-beta with anti-IL-10 and anti-TGF-beta antibodies, respectively, did not affect the intracellular growth of MAIC in macrophages from mice with BcgS (MAIC-susceptible) or BcgI (MAIC-resistant) genotype, regardless of the virulence of test MAIC strains. The same result was also obtained for macrophages stimulated with IFN-gamma or TNF-alpha. Third, in MAIC-infected mice, the growth of organisms at the sites of infection (lungs and spleens) was not affected by administration of anti-IL-10 or anti-TGF-beta antibodies. These findings indicate that, in the case of mice, endogenous IL-10 and TGF-beta are essentially ineffective in down-regulating macrophage anti-MAIC functions not only in vitro but also in vivo.

Effects of the Chinese traditional medicine mao-bushi-saishin-to on therapeutic efficacy of a new benzoxazinorifamycin, KRM-1648, against Mycobacterium avium infection in mice

The Chinese traditional medicine mao-bushi-saishin-to (MBST), which has anti-inflammatory effects and has been used to treat the common cold and nasal allergy in Japan, was examined for its effects on the therapeutic activity of a new benzoxazinorifamycin, KRM-1648 (KRM), against Mycobacterium avium complex (MAC) infection in mice. In addition, we examined the effects of MBST on the anti-MAC activity of murine peritoneal macrophages (M phi s). First, MBST significantly increased the anti-MAC therapeutic activity of KRM when given to mice in combination with KRM, although MBST alone did not exhibit such effects. Second, MBST treatment of M phi s significantly enhanced the KRM-mediated killing of MAC bacteria residing in M phi s, although MBST alone did not potentiate the M phi anti-MAC activity. MBST-treated M phi s showed decreased levels of reactive nitrogen intermediate (RNI) release, suggesting that RNIs are not decisive in the expression of the anti-MAC activity of such M phi populations. MBST partially blocked the interleukin-10 (IL-10) production of MAC-infected M phi s without affecting their transforming growth factor beta (TGF-beta)-producing activity. Reverse transcription-PCR analysis of the lung tissues of MAC-infected mice at weeks 4 and 8 after infection revealed a marked increase in the levels of tumor necrosis factor alpha, gamma interferon (IFN-gamma), IL-10, and TGF-beta mRNAs. KRM treatment of infected mice tended to decrease the levels of the test cytokine mRNAs, except that it increased TGF-beta mRNA expression at week 4. MBST treatment did not affect the levels of any cytokine mRNAs at week 8, while it down-regulated cytokine mRNA expression at week 4. At week 8, treatment of mice with a combination of KRM and MBST caused a marked decrease in the levels of the test cytokines mRNAs, especially IL-10 and IFN-gamma mRNAs, although such effects were obscure at week 4. These findings suggest that down-regulation of the expression of IL-10 and TGF-beta is related to the combined therapeutic effects of KRM and MBST against MAC infection.

Therapeutic effects of benzoxazinorifamycin KRM-1648 administered alone or in combination with a half-sized secretory leukocyte protease inhibitor or the nonsteroidal anti-inflammatory drug diclofenac sodium against Mycobacterium avium complex infection in mice

The effects of half-sized secretory leukocyte protease inhibitor or diclofenac sodium administered alone or in combination with the benzoxazinorifamycin KRM-1648 on the therapeutic efficacy of KRM-1648 against Mycobacterium avium complex (MAC) in mice were studied. Neither of the two anti-inflammatory drugs affected the efficacy of KRM-1648, while they exerted significant modulating effects on tumor necrosis factor alpha production by MAC-infected macrophages.

Effects of Yokuinin on the therapeutic efficacy of a new benzoxazinorifamycin KRM-1648 against Mycobacterium avium infection

The Chinese traditional medicine, Yokuinin, which has anti-inflammatory effects and anti-human papilloma virus activity, was examined for its effects on the therapeutic efficacy of a benzoxazinorifamycin KRM-1648 (KRM) against Myobacterium avium infection in mice. Reverse transcription-PCR analysis revealed that Yokuinin increased the mRNA expression of all test cytokines in lung tissues of infected ice at week 8, in the order transforming growth factor-beta (TGF-beta) > IFN-gamma > TNF-alpha > IL-10. Mice given Yokuinin in combination with KRM had higher levels of TFG-beta mRNA expression than did mice given KRM alone, indicating that TGF-beta plays an important role in the expression of the anti-inflammatory effect of Yokuinin in vivo. Yokuinin reduced IL-10 production by M. avium-infected macrophages ph. (M phis) but did not affect M phi TFG-beta production. Although Yokuinin significantly modified cytokine expression in M. avium-infected mice, this drug did not influence the therapeutic efficacy of KRM against M. avium infection, suggesting that administration of Yokuinin in combination with KRM to the patients with M. avium infection does not cause severe disadvantages.

Evaluation of in vivo therapeutic efficacy of a new benzoxazinorifamycin, KRM-1648, in SCID mouse model for disseminated Mycobacterium avium complex infection

In this study, profiles of infection due to Mycobacterium avium complex (MAC) in CB-17 SCID mice deficient in T and B cell functions were examined, when mice were given or not given a new benzoxazinorifamycin, KRM-1648 (KRM), during the course of infection. When mice were infected intravenously with MAC, the bacterial loads in their visceral organs were larger than those of their co-isogenic CB-17 counterparts. The incidence and the degree of gross lung lesions were less in SCID mice compared to CB-17 mice. Athymic BALB/c nude mice showed similar profiles of the infection. Beige mice showed more severe gross lesions and larger bacterial loads in the lungs than did SCID and athymic BALB/c nude mice. When MAC was infected subcutaneously into the hind footpads of mice, disseminated growth of organisms in the footpads, blood, and visceral organs was seen in SCID mice, but not in CB-17 or BALB/c mice. KRM exhibited the same level of therapeutic effect on SCID mice infected with MAC via the intravenous route in terms of inhibiting bacterial growth in the lungs and kidneys, as in cases of CB-17 and BALB/c mice with normal T-cell functions. In beige mice, the degree of growth inhibition of MAC due to KRM treatment was significantly greater than that achieved in SCID mice.