Yersinia pestis, keuhkorutto indusoituvan HO-1 i:n terapeuttinen potentiaali. Hemianalogi kobolttiprotoporfyriini yriinin(CoPP)

https://aac.asm.org/content/64/4/e01819-19etin tämän myös  ystäville Facebookiin:  keuhkoruton muutoksia vähentämään  ( koehiirillä) on  kehitetty  malli. Hypoteesi:  indusoituvan  hemioksygenaasi1:n  aktivoiminen  hemianalogilla CoPP, kobolttiprotoporfyriinilla,  esti noita keuhkoruttomuutoksia.

Experimental Therapeutics

Activation of Heme Oxygenase Expression by Cobalt Protoporphyrin Treatment Prevents Pneumonic Plague Caused by Inhalation of Yersinia pestis

Joshua L. Willix, Jacob L. Stockton, Rachel M. Olson, Paul E. Anderson, Deborah M. Anderson

DOI: 10.1128/AAC.01819-19

ABSTRACT

Pneumonic plague, caused by the Gram-negative bacteria Yersinia pestis, is an invasive, rapidly progressing disease with poor survival rates. Following inhalation of Y. pestis, bacterial invasion of the lungs and a tissue-damaging inflammatory response allows vascular spread of the infection. Consequently, primary pneumonic plague is a multiorgan disease involving sepsis and necrosis of immune tissues and the liver, as well as bronchopneumonia and rampant bacterial growth. Given the likely role of the hyperinflammatory response in accelerating the destruction of tissue, in this work we evaluated the therapeutic potential of the inducible cytoprotective enzyme heme oxygenase 1 (HO-1) against primary pneumonic plague. On its own, the HO-1 inducer cobalt protoporphyrin IX (CoPP) provided mice protection from lethal challenge with Y. pestis CO92 with improved pulmonary bacterial clearance and a dampened inflammatory response compared to vehicle-treated mice. Furthermore, CoPP treatment combined with doxycycline strongly enhanced protection in a rat aerosol challenge model. Compared to doxycycline alone, CoPP treatment increased survival, with a 3-log decrease in median bacterial titer recovered from the lungs and the general absence of a systemic hyperinflammatory response. In contrast, treatment with the HO-1 inhibitor SnPP had no detectable impact on doxycycline efficacy. The combined data indicate that countering inflammatory toxicity by therapeutically inducing HO-1 is effective in reducing the rampant growth of Y. pestis and preventing pneumonic plague.

DISCUSSION

Pneumonic plague is a deadly disease that consists of fulminant bronchopneumonia and severe sepsis. In this work, we showed that this can be prevented by treatment with the heme analog and inducer of HO-1 expression, cobalt protoporphyrin IX. On its own, CoPP treatment of mice appeared to reduce inflammatory toxicity, rather than suppress cytokine production during pulmonary Y. pestis infection. This allowed for improved bacterial clearance by the innate immune response. Synergistic protection with antibiotics was observed in a rat doxycycline treatment model. Since it is known that doxycycline efficacy is dependent on host neutrophils, these data suggest that HO-1 may improve the neutrophilic response to Y. pestis (40).

Previous work has established a role for HO-1 in improving the bactericidal mechanisms of neutrophils, and in decreasing damage to tissues caused by release of reactive oxygen species (ROS) by neutrophils (41, 42). In oxygen-rich environments, such as the lungs, free iron generated as a result of hemolysis leads to the generation of ROS that is proinflammatory and cytotoxic to cells (21). Highly virulent and invasive pathogens, such as Y. pestis, are likely able to exploit this response and grow, resulting in a feedback loop of neutrophilic inflammation and tissue damage that favors bacterial growth. Further protection from ROS may be provided by biliverdin and CO, produced by heme degradation, which have antiapoptotic and anti-inflammatory effects that could dampen immunopathology (22). Future work examining the activity of CoPP-treated macrophages or neutrophils in vitro and in vivo should be informative in understanding which, if any, of these mechanisms results in protection from pneumonic plague.

CoPP allows for Nrf2-regulated gene expression, an anti-oxidant program with pleiotropic effects, including an overall suppression of the inflammatory response (26). During Y. pestis infection of mice, however, this response was not observed, and in fact, increased IL-6 was found. This may be a consequence of modulation of host cell signaling by Y. pestis virulence factors or is an indication that essential costimulatory signals were not present. Without doxycycline, CoPP provided moderate protection and, in fact, it appeared that loss of protection may have been caused by off-target effects. For example, we found abnormally low ALP, elevated IL-6, and other modest changes in the serum of mice in the CoPP treatment group that may suggest liver toxicity. Other heme-binding proteins, primarily cytochrome P450 in the liver, are known to bind to and be inhibited by CoPP (43). Alternatively, overproduction of HO-1 in the liver may have unwanted effects (44). Additional investigation is needed to understand the mechanism underlying these observations, whether it is caused by HO-1 or CoPP directly, and whether reducing this effect improves protection. Nevertheless, the targeting of HO-1 or another cytoprotective mechanism to limit inflammatory damage is a promising treatment strategy for pneumonic plague.

Here, we observed an unexpected difference between male and female SD rats in their susceptibility to aerosol challenge with Y. pestis. In human plague, there are no known sex dependent differences in susceptibility, though historically, there have been more male than female plague victims, Sexual dimorphism has been frequently documented in infectious diseases, and in general, females show greater humoral and cell mediated responses than males of the same age and species, making females more resistant (45). In contrast, in the pneumonic plague model, SD rat females were more sensitive to infection by aerosolized Y. pestis, suggesting the effects we observed may result from the unique host-pathogen interactions that define plague. Since the disease course appeared to have the same kinetics and outcome in both sexes, we think it likely that the difference in susceptibility relates to an early event that impacts the initiation of infection. In an endotoxin challenge model, the inflammatory response of the SD rat female involved higher production of inflammatory cytokines from alveolar macrophages (46). Alveolar macrophages are early cellular targets of Y. pestis infection of the lungs, where such an effect could impact the initiation of infection (47). Future treatment and vaccine studies of plague should include male and female animals until there is a better understanding of the mechanism underlying sex-dependent susceptibility in the SD rat.