Heme Oxygenase-1 Deficiency Diminishes Methicillin-Resistant Staphylococcus aureus Clearance Due to Reduced TLR9 Expression in Pleural Mesothelial Cells

High prevalence of Merkel cell polyomavirus is associated with dysregulation in transcript levels of TLR9 and type I IFNs in a large cohort of CF patients from the Italian (Lazio) reference center for cystic fibrosis

Merkel cell polyomavirus (MCPyV) has been detected in respiratory specimens including those from Cystic Fibrosis (CF) patients, raising questions about its immunological and clinical relevance in the respiratory tract. MCPyV might promote an inappropriate antiviral response contributing to a chronic inflammatory response and resulting in detrimental effects in CF. Respiratory samples (n = 1138) were randomly collected from respiratory tract of CF patients (n = 539) during July 2018-October 2019. MCPyV-DNA detection was performed by Real Time-PCR and positive samples were characterized by sequencing of the NCCR genomic region. The transcript levels of Toll-like receptor 9 (TLR9) and type I interferon (IFN-I) genes (IFNα, IFNβ and IFNε) were examined by RT/Real Time-PCR assays. MCPyV-DNA was detected in 268 out of 1138 respiratory specimens (23.5%) without any difference in the prevalence of MCPyV-DNA according to age, gender or bacteriological status of CF individuals. Thirteen out of 137 CF patients remained positive for MCPyV-DNA over the time (a median follow-up period of 8.8 months). Detection of MCPyV-DNA in respiratory specimens was not associated with the occurrence of exacerbation events. Both MCPyV positive adolescents (11-24 years) and adults (>25 years) had lower mRNA levels of TLR9, IFNβ, IFNε and IFNα than the negative patients of the same age group, while MCPyV positive children produced increased levels of TLR9 and IFN-I genes (p < 0.05 for TLR9, IFNβ, IFNε) with respect to the negative ones. There were significant differences in TLR9 levels (p < 0.01), but not in those of IFNs, between MCPyV-DNA positive and negative patients with S. aureus, P. aeruginosa or both. Overall, these results indicate that MCPyV-DNA is frequently detected in the respiratory samples of CF patients and might influence the expression levels of IFN-related genes in an age dependent manner. The concomitant detection of MCPyV together with S. aureus and/or P. aeruginosa correlated with alterations in TLR9 levels suggesting that virus-bacteria coinfections might contribute to affect antiviral immunity in CF patients.

The Role of Iron in Staphylococcus aureus Infection and Human Disease: A Metal Tug of War at the Host—Microbe Interface

Iron deficiency anemia can be treated with oral or intravenous Fe supplementation. Such supplementation has considerable effects on the human microbiome, and on opportunistic pathogenic micro-organisms. Molecular understanding of the control and regulation of Fe availability at the host-microbe interface is crucial to interpreting the side effects of Fe supplementation. Here, we provide a concise overview of the regulation of Fe by the opportunistic pathogen Staphylococcus aureus. Ferric uptake regulator (Fur) plays a central role in controlling Fe uptake, utilization and storage in order to maintain a required value. The micro-organism has a strong preference for heme iron as an Fe source, which is enabled by the Iron-regulated surface determinant (Isd) system. The strategies it employs to overcome Fe restriction imposed by the host include: hijacking host proteins, replacing metal cofactors, and replacing functions by non-metal dependent enzymes. We propose that integrated omics approaches, which include metalloproteomics, are necessary to provide a comprehensive understanding of the metal tug of war at the host-microbe interface down to the molecular level.

CORM-2 inhibits intracerebral hemorrhage-mediated inflammation

Background and purpose: Low-dose of carbon monoxide delivered by CO-releasing molecule-2 (CORM-2) had been confirmed having anti-inflammatory efficacy in some inflammatory diseases. Herein, we assessed the usefulness of CORM-2 in correcting intracerebral hemorrhage (ICH)-mediated inflammation.Methods: Healthy male Sprague Dawley (SD) rats randomly entered into four groups: sham-ICH, ICH, ICH+CORM-2, and ICH+ inactive carbon monoxide releasing molecule 2 (iCORM-2). ICH was induced by 50 μl of autologous arterial blood injected in situ in the rat brain. Neuro-functions of the ICH rats were evaluated with Garcia 18 scores at the 6th, 24th , 48th hou, and the fifthh day post-ICH. And brain tissues surrounding the hematoma area were collected from all ICH rats and assayed with Western blot and immunofluoresence analysis.Results: Neuro-dysfunctions in ICH rats were very severe than those in ICH +CORM-2 rats. Compared to sham group, the levels of HO-1, IKKβ, NF-κB, and TNF-α in ICH group began to elevate at the 6th hour, and reached to peak at the 48th hour post-ICH, all p < 0.05. While in ICH +CORM-2 group, the expressions of IKKβ, NF-κB, and TNF-α were very weaker than that in ICH group at every time points mentioned above; however, this phenomenon was not reproduced in ICH + iCORM-2 group. HO-1 in ICH+CORM-2 group highlighted in perihematomal area with many activated microglia (Iba-1-positive cells) and co-expressed with TNF-α, all of which were diminished at the fifth day post-ICH.Conclusion: CORM-2 may attenuate ICH-mediated inflammation by inhibiting microglial activation, which may involve the IKK/NF-κB pathway.AbbreviationsICH: intracerebral hemorrhage; CO: carbon monoxide; CORM-2: carbon monoxide releasing molecule-2; iCORM-2: inactive carbon monoxide releasing molecule-2; HO-1: heme oxygenase 1; IKKβ: inhibitor of IκB kinases β; NF-κB: nuclear factor-κB; TNF-α: tumor necrosis factor-α; Iba-1: ionized calcium binding adaptor molecule-1; IκB: inhibitor of NF-κB; iNOS: inducible nitric oxide synthase; Keap1: Kelch-like ECH-associated protein 1; Nrf2: NF-E2-related factor 2; DMSO: dimethylsulfoxide.

Host heme oxygenase-1: Friend or foe in tackling pathogens?

Infectious diseases are a major challenge in management of human health worldwide. Recent literature suggests that host immune system could be modulated to ameliorate the pathogenesis of infectious disease. Heme oxygenase (HMOX1) is a key regulator of cellular signaling and it could be modulated using pharmacological reagents. HMOX1 is a cytoprotective enzyme that degrades heme to generate carbon monoxide (CO), biliverdin, and molecular iron. CO and biliverdin (or bilirubin derived from it) can restrict the growth of a few pathogens. Both of these also induce antioxidant pathways and anti-inflammatory pathways. On the other hand, molecular iron can induce proinflammatory pathway besides making the cellular environment oxidative in nature. Since microbial infections often induce oxidative stress in host cells/tissues, role of HMOX1 has been analyzed in the pathogenesis of number of infections. In this review, we have described the role of HMOX1 in pathogenesis of bacterial infections caused by Mycobacterium species, Salmonella and in microbial sepsis. We have also provided a succinct overview of the role of HMOX1 in parasitic infections such as malaria and leishmaniasis. In the end, we have also elaborated the role of HMOX1 in viral infections such as AIDS, hepatitis, dengue, and influenza. © 2018 IUBMB Life, 70(9):869-880, 2018.

Antimycobacterial effect of IFNG (interferon gamma)-induced autophagy depends on HMOX1 (heme oxygenase 1)-mediated increase in intracellular calcium levels and modulation of PPP3/calcineurin-TFEB (transcription factor EB) axis

IFNG (interferon gamma)-induced autophagy plays an important role in the elimination of intracellular pathogens, such as Mycobacterium tuberculosis (Mtb). However, the signaling cascade that leads to the increase in autophagy flux in response to IFNG is poorly defined. Here, we demonstrate that HMOX1 (heme oxygenase 1)-generated carbon monoxide (CO) is required for the induction of autophagy and killing of Mtb residing in macrophages in response to immunomodulation by IFNG. Interestingly, IFNG exposure of macrophages induces an increase in intracellular calcium levels that is dependent on HMOX1 generated CO. Chelation of intracellular calcium inhibits IFNG-mediated autophagy and mycobacterial clearance from macrophages. Moreover, we show that IFNG-mediated increase in intracellular calcium leads to activation of the phosphatase calcineurin (PPP3), which dephosphorylates the TFEB (transcription factor EB) to induce autophagy. PPP3-mediated activation and nuclear translocation of TFEB are critical in IFNG-mediated mycobacterial trafficking and survival inside the infected macrophages. These findings establish that IFNG utilizes the PPP3-TFEB signaling axis for inducing autophagy and regulating mycobacterial growth. We believe this signaling axis could act as a therapeutic target for suppression of growth of intracellular pathogens.

Role of heme oxygenase-1 in potentiation of phagocytic activity of macrophages by taurine chloramine: Implications for the resolution of zymosan A-induced murine peritonitis

Phagocytosis of pathogens by macrophages is crucial for the successful resolution of inflammation induced by microbial infection. Taurine chloramine (TauCl), an endogenous anti-inflammatory and antioxidative substance, is produced by reaction between taurine and hypochlorous acid by myeloperoxidase activity in neutrophils under inflammatory conditions. In the present study, we investigated the effect of TauCl on resolution of acute inflammation caused by fungal infection using a zymosan A-induced murine peritonitis model. TauCl administration reduced the number of the total peritoneal leukocytes, while it increased the number of peritoneal monocytes. Furthermore, TauCl promoted clearance of pathogens remaining in the inflammatory environment by macrophages. When the macrophages isolated from thioglycollate-treated mice were treated with TauCl, their phagocytic capability was enhanced. In the murine macrophage-like RAW264.7 cells treated with TauCl, the proportion of macrophages clearing the zymosan A particles was also increased. TauCl administration resulted in elevated expression of heme oxygenase-1 (HO-1) in the peritoneal macrophages. Pharmacologic inhibition of HO-1 activity or knockdown of HO-1 in the murine macrophage RAW264.7 cells abolished the TauCl-induced phagocytosis, whereas the overexpression of HO-1 augmented the phagocytic ability of macrophages. Moreover, peritoneal macrophages isolated from HO-1 null mice failed to mediate TauCl-induced phagocytosis. Our results suggest that TauCl potentiates phagocytic activity of macrophages through upregulation of HO-1 expression.