Protective Role of Bacillus anthracis Exosporium in Macrophage-Mediated Killing by Nitric Oxide

ABSTRACT The ability of the endospore-forming, gram-positive bacterium Bacillus anthracis to survive in activated macrophages is key to its germination and survival. In a previous publication, we discovered that exposure of primary murine macrophages to B. anthracis endospores upregulated NOS 2 concomitant with an ·NO-dependent bactericidal response. Since NOS 2 also generates O2·−, experiments were designed to determine whether NOS 2 formed peroxynitrite (ONOO−) from the reaction of ·NO with O2·− and if so, was ONOO− microbicidal toward B. anthracis. Our findings suggest that ONOO− was formed upon macrophage infection by B. anthracis endospores; however, ONOO− does not appear to exhibit microbicidal activity toward this bacterium. In contrast, the exosporium of B. anthracis, which exhibits arginase activity, protected B. anthracis from macrophage-mediated killing by decreasing ·NO levels in the macrophage. Thus, the ability of B. anthracis to subvert ·NO production has important implications in the control of B. anthracis-induced infection.

Download Full-text

The Protective Role of Bacillus Anthracis Exosporium in Macrophage-Mediated Killing by Nitric Oxide

ASME 2007 Summer Bioengineering Conference ◽

10.1115/sbc2007-176138 ◽

2007 ◽

Author(s):

John Weaver ◽

Tae Jin Kang ◽

Kimberly Raines ◽

Guan-Liang Cao ◽

Stephen Hibbs ◽

...

Keyword(s):

Nitric Oxide ◽

Bacillus Anthracis ◽

Protective Role ◽

Oxygen Species ◽

Activated Macrophages ◽

Positive Bacterium ◽

Bacterium Bacillus ◽

Oxide Synthase ◽

Inducible Nitric Oxide

The ability of the endospore-forming, gram-positive bacterium Bacillus anthracis to survive exposure to antibacterial killing mechanisms by activated macrophages is key to its germination and survival. These antibacterial killing mechanisms include, but are not limited to the generation of free radicals such as nitric oxide (•NO) and superoxide (O2•−) from the upregulation of inducible nitric oxide synthase (NOS 2) along with products derived from them, e.g., peroxynitrite (ONOO−), as part of microbicidal activity. However questions still remain as to how these species are involved in microbial killing, specifically with respect to B. anthracis. In a previous study, we demonstrated that exposure of primary murine macrophages to sonicated B. anthracis endospores up-regulated NOS 2 and demonstrated a •NO-dependent bactericidal response, but unanswered in that study was which of the NOS 2-derived reactive oxygen species was responsible for the observed bactericidal response. Since NOS 2 also generates O2•−, experiments were designed to determine whether NOS 2 formed ONOO− from the reaction of •NO with O2•− and if so, was ONOO− microbicidal toward B. anthracis.

Download Full-text

Role of iron in the nitric oxide-mediated fungicidal mechanism of IFN-gamma-activated murine macrophages against Paracoccidioides brasiliensis conidia

Revista do Instituto de Medicina Tropical de São Paulo ◽

10.1590/s0036-46652007000100003 ◽

2007 ◽

Vol 49 (1) ◽

pp. 11-16 ◽

Cited By ~ 9

Author(s):

Angel Gonzalez ◽

Angela Restrepo ◽

Luz E. Cano

Keyword(s):

Nitric Oxide ◽

Paracoccidioides Brasiliensis ◽

No Production ◽

Activated Macrophages ◽

Systemic Mycosis ◽

Ifn Gamma ◽

Murine Macrophages ◽

Marked Inhibition ◽

Essential Growth

Iron is an essential growth element of virtually all microorganisms and its restriction is one of the mechanisms used by macrophages to control microbial multiplication. Paracoccidioides brasiliensis, the agent of paracoccidioidomycosis, an important systemic mycosis in Latin America, is inhibited in its conidia-to-yeast conversion in the absence of iron. We studied the participation of iron in the nitric oxide (NO)-mediated fungicidal mechanism against conidia. Peritoneal murine macrophages activated with 50U/mL of IFN-gamma or treated with 35 µM Deferoxamine (DEX) and infected with P. brasiliensis conidia, were co-cultured and incubated for 96 h in the presence of different concentrations of holotransferrin (HOLO) and FeS0(4). The supernatants were withdrawn in order to assess NO2 production by the Griess method. The monolayers were fixed, stained and observed microscopically. The percentage of the conidia-to-yeast transition was estimated by counting 200 intracellular propagules. IFN-gamma-activated or DEX-treated Mthetas presented marked inhibition of the conidia-to-yeast conversion (19 and 56%, respectively) in comparison with non-activated or untreated Mthetas (80%). IFN-gamma-activated macrophages produced high NO levels in comparison with the controls. Additionally, when the activated or treated-macrophages were supplemented with iron donors (HOLO or FeSO4), the inhibitory action was reversed, although NO production remained intact. These results suggest that the NO-mediated fungicidal mechanism exerted by IFN-gamma-activated macrophages against P. brasiliensis conidia, is dependent of an iron interaction.

Download Full-text

Losartan Increases No Production from the Bovine Aortic Wall That is Stimulated by Angiotensin II

European Journal of Inflammation ◽

10.1177/1721727x0300100304 ◽

2003 ◽

Vol 1 (3) ◽

pp. 113-117 ◽

Cited By ~ 1

Author(s):

M. Myronidou ◽

B. Kokkas ◽

A. Kouyoumtzis ◽

N. Gregoriadis ◽

A. Lourbopoulos ◽

...

Keyword(s):

Nitric Oxide ◽

Angiotensin Ii ◽

Aortic Wall ◽

Vascular Wall ◽

Protective Role ◽

Normal Function ◽

No Production ◽

Chemical Inactivation

In these studies we investigated if losartan, an AT1- receptor blocker has any beneficial effect on NO production from the bovine aortic preparations in vitro while under stimulation from angiotensin II. Experiments were performed on intact specimens of bovine thoracic aorta, incubated in Dulbeco's MOD medium in a metabolic shaker for 24 hours under 95 % O2 and 5 % CO2 at a temperature of 37°C. We found that angiotensin II 1nM−10 μM does not exert any statistically significant action on NO production. On the contrary, angiotensin II 10nM increases the production of NO by 58.14 % (from 12.16 + 2.9 μm/l to 19.23 + 4.2 μm/l in the presence of losartan 1nM (P<0.05). Nitric oxide levels depend on both rate production and rate catabolism or chemical inactivation. Such an equilibrium is vital for the normal function of many systems including the cardiovascular one. The above results demonstrate that the blockade of AT1-receptors favors the biosynthesis of NO and indicate the protective role of losartan on the vascular wall.

Download Full-text

Protective Role of Nitric Oxide inStaphylococcus aureus Infection in Mice

Infection and Immunity ◽

10.1128/iai.66.3.1017-1022.1998 ◽

1998 ◽

Vol 66 (3) ◽

pp. 1017-1022 ◽

Cited By ~ 65

Author(s):

Sanae Sasaki ◽

Tomisato Miura ◽

Shinsuke Nishikawa ◽

Kyogo Yamada ◽

Mayuko Hirasue ◽

...

Keyword(s):

Nitric Oxide ◽

Spleen Cell ◽

Cell Cultures ◽

Protective Role ◽

Inos Mrna ◽

No Production ◽

Necrosis Factor Alpha ◽

Tnf Α ◽

Ifn Γ

ABSTRACT This study was carried out to determine the role of nitric oxide (NO) in Staphylococcus aureus infection in mice. NO production in spleen cell cultures was induced by heat-killed S. aureus. Expression of mRNA of the inducible isoform of NO synthase (iNOS) was induced in the spleens and kidneys of S. aureus-infected mice. When mice were treated with monoclonal antibodies (MAbs) against tumor necrosis factor alpha (TNF-α) or gamma interferon (IFN-γ) before S. aureus infection, the induction of iNOS mRNA expression in the kidneys was inhibited. These MAbs also inhibited NO production in spleen cell cultures stimulated with heat-killed S. aureus. NO production in the spleen cell cultures and levels of urinary nitrate plus nitrite were suppressed by treatment with aminoguanidine (AG), a selective inhibitor of iNOS. The survival rates of AG-treated mice were significantly decreased by either lethal or sublethal S. aureusinfections. However, an effect of AG administration on bacterial growth was not observed in the spleens and kidneys of mice during either type of infection. Production of TNF-α and IFN-γ was not affected by AG treatment in vitro and in vivo. These results suggest that NO plays an important role in protection from lethality by the infection, but the protective role of NO in host resistance against S. aureusinfection was not proved. Moreover, our results show that TNF-α and IFN-γ regulate NO production while NO may not be involved in the regulation of the production of these cytokines during S. aureus infection.

Download Full-text

Novel role of the nitrite transporter NirC in Salmonella pathogenesis: SPI2-dependent suppression of inducible nitric oxide synthase in activated macrophages

Microbiology ◽

10.1099/mic.0.029611-0 ◽

2009 ◽

Vol 155 (8) ◽

pp. 2476-2489 ◽

Cited By ~ 40

Author(s):

Priyanka Das ◽

Amit Lahiri ◽

Ayan Lahiri ◽

Dipshikha Chakravortty

Keyword(s):

Nitric Oxide ◽

Type Strain ◽

Wild Type Strain ◽

No Production ◽

Activated Macrophages ◽

Wild Type ◽

Raw264.7 Macrophages ◽

Oxide Synthase ◽

Inducible Nitric Oxide

Activation of macrophages by interferon gamma (IFN-γ) and the subsequent production of nitric oxide (NO) are critical for the host defence against Salmonella enterica serovar Typhimurium infection. We report here the inhibition of IFN-γ-induced NO production in RAW264.7 macrophages infected with wild-type Salmonella. This phenomenon was shown to be dependent on the nirC gene, which encodes a potential nitrite transporter. We observed a higher NO output from IFN-γ-treated macrophages infected with a nirC mutant of Salmonella. The nirC mutant also showed significantly decreased intracellular proliferation in a NO-dependent manner in activated RAW264.7 macrophages and in liver, spleen and secondary lymph nodes of mice, which was restored by complementing the gene in trans. Under acidified nitrite stress, a twofold more pronounced NO-mediated repression of SPI2 was observed in the nirC knockout strain compared to the wild-type. This enhanced SPI2 repression in the nirC knockout led to a higher level of STAT-1 phosphorylation and inducible nitric oxide synthase (iNOS) expression than seen with the wild-type strain. In iNOS knockout mice, the organ load of the nirC knockout strain was similar to that of the wild-type strain, indicating that the mutant is exclusively sensitive to the host nitrosative stress. Taken together, these results reveal that intracellular Salmonella evade killing in activated macrophages by downregulating IFN-γ-induced NO production, and they highlight the critical role of nirC as a virulence gene.

Download Full-text

The Protective Role of Bacillus anthracis Exosporium in Macrophage‐Mediated Killing by Nitric Oxide

The FASEB Journal ◽

10.1096/fasebj.21.5.a624 ◽

2007 ◽

Vol 21 (5) ◽

Author(s):

John Weaver ◽

Tae Jin Kang ◽

Kimberly Raines ◽

Guan‐Liang Cao ◽

Stephen Hibbs ◽

...

Keyword(s):

Nitric Oxide ◽

Bacillus Anthracis ◽

Protective Role

Download Full-text

The Signaling Pathways in Nitric Oxide Production by Neutrophils Exposed to N-nitrosodimethylamine

Letters in Drug Design & Discovery ◽

10.2174/1570180815666180426121503 ◽

2018 ◽

Vol 16 (2) ◽

pp. 194-199

Author(s):

Wioletta Ratajczak-Wrona ◽

Ewa Jablonska

Keyword(s):

Nitric Oxide ◽

Signaling Pathways ◽

Molecular Mechanisms ◽

Polymorphonuclear Neutrophils ◽

Microbial Pathogens ◽

Human Neutrophils ◽

No Production ◽

Oxide Synthase ◽

Inducible Nitric Oxide

Background: Polymorphonuclear neutrophils (PMNs) play a crucial role in the innate immune system’s response to microbial pathogens through the release of reactive nitrogen species, including Nitric Oxide (NO). </P><P> Methods: In neutrophils, NO is produced by the inducible Nitric Oxide Synthase (iNOS), which is regulated by various signaling pathways and transcription factors. N-nitrosodimethylamine (NDMA), a potential human carcinogen, affects immune cells. NDMA plays a major part in the growing incidence of cancers. Thanks to the increasing knowledge on the toxicological role of NDMA, the environmental factors that condition the exposure to this compound, especially its precursors- nitrates arouse wide concern. Results: In this article, we present a detailed summary of the molecular mechanisms of NDMA’s effect on the iNOS-dependent NO production in human neutrophils. Conclusion: This research contributes to a more complete understanding of the mechanisms that explain the changes that occur during nonspecific cellular responses to NDMA toxicity.

Download Full-text