Lovastatin protects against experimental plague in mice

Chronic Leptin Deficiency Improves Tolerance of Physiological Damage and Host-Pathogen Cooperation during Yersinia pseudotuberculosis Infection

To combat infections, hosts employ a combination of antagonistic and cooperative defense strategies. The former refers to pathogen killing mediated by resistance mechanisms, while the latter refers to physiological defense mechanisms that promote host health during infection independent of pathogen killing, leading to an apparent cooperation between the host and the pathogen. Previous work has shown that Leptin, a pleiotropic hormone that plays a central role in regulating appetite and energy metabolism, is indispensable for resistance mechanisms, while a role for Leptin signaling in cooperative host-pathogen interactions remains unknown. Using a mouse model of Yersinia pseudotuberculosis (Yptb) infection, an emerging pathogen that causes fever, diarrhea, and mesenteric lymphadenitis in humans, we found that the physiological effects of chronic Leptin-signaling deficiency conferred protection from Yptb infection due to increased host-pathogen cooperation rather than greater resistance defenses. The protection against Yptb infection was independent of differences in food consumption, lipolysis, or fat mass. Instead, we found that the chronic absence of Leptin signaling protects from a shift to lipid utilization during infection that contributes to Yptb lethality. Furthermore, we found that the survival advantage conferred by Leptin deficiency was associated with increased liver and kidney damage. Our work reveals an additional level of complexity for the role of Leptin in infection defense and demonstrates that in some contexts, in addition to tolerating the pathogen, tolerating organ damage is more beneficial for survival than preventing the damage.

Antibiotic Therapy of Plague: A Review

Plague-a deadly disease caused by the bacterium Yersinia pestis-is still an international public health concern. There are three main clinical forms: bubonic plague, septicemic plague, and pulmonary plague. In all three forms, the symptoms appear suddenly and progress very rapidly. Early antibiotic therapy is essential for countering the disease. Several classes of antibiotics (e.g., tetracyclines, fluoroquinolones, aminoglycosides, sulfonamides, chloramphenicol, rifamycin, and β-lactams) are active in vitro against the majority of Y. pestis strains and have demonstrated efficacy in various animal models. However, some discrepancies have been reported. Hence, health authorities have approved and recommended several drugs for prophylactic or curative use. Only monotherapy is currently recommended; combination therapy has not shown any benefits in preclinical studies or case reports. Concerns about the emergence of multidrug-resistant strains of Y. pestis have led to the development of new classes of antibiotics and other therapeutics (e.g., LpxC inhibitors, cationic peptides, antivirulence drugs, predatory bacteria, phages, immunotherapy, host-directed therapy, and nutritional immunity). It is difficult to know which of the currently available treatments or therapeutics in development will be most effective for a given form of plague. This is due to the lack of standardization in preclinical studies, conflicting data from case reports, and the small number of clinical trials performed to date.

Statins: a viable candidate for host-directed therapy against infectious diseases

Statins were first identified over 40 years ago as lipid-lowering drugs and have been remarkably effective in treating cardiovascular diseases. As research advanced, the protective effects of statins were additionally attributed to their anti-inflammatory, antioxidative, anti-thrombotic and immunomodulatory functions rather than lipid-lowering abilities alone. By promoting host defence mechanisms and inhibiting pathological inflammation, statins increase survival in human infectious diseases. At the cellular level, statins inhibit the intermediates of the host mevalonate pathway, thus compromising the immune evasion strategies of pathogens and their survival. Here, we discuss the potential use of statins as an inexpensive and practical alternative or adjunctive host-directed therapy for infectious diseases caused by intracellular pathogens, such as viruses, protozoa, fungi and bacteria.

Farnesyltransferase inhibitor FTI-277 inhibits PD-L1 expression on septic spleen lymphocytes and promotes spleen lymphocyte activation

Farnesyltransferase inhibitors have been tested in clinical trials for the treatment of tumours. In sepsis, the binding of programmed death 1 (PD-1) to programmed death ligand 1 (PD-L1) promotes lymphocyte apoptosis and decreases cytokine expression, thus affecting survival rates. The PD-1/PD-L1 pathway plays an important role in chronic viral infection, bacterial infection and sepsis. However, the precise immunosuppressive and anti-inflammatory functions of this pathway remain poorly understood. In our previous study, the induction of sepsis by caecal ligation and puncture (CLP) resulted in increased farnesyltransferase activity and farnesylated protein levels in the spleen relative to sham treatment. However, the effect of inhibition of farnesyltransferase activity on overall survival rates in patients with sepsis and the specific signalling pathway involved remain to be investigated. In this study, mice with CLP-induced sepsis were treated with farnesyltransferase inhibitor (FTI-277), and PD-L1 expression on septic spleen lymphocytes was examined. Flow cytometric analysis revealed that PD-L1 is expressed constitutively on lymphocytes and that PD-L1 protein expression was up-regulated strongly following CLP. FTI-277 down-regulated PD-L1 mRNA and protein expression on septic spleen lymphocytes in a dose-dependent manner. This effect was associated closely with nuclear factor kappa B (NF-κB). In addition, the significant damping effect of FTI-277 on the PD-L1 signal promoted interferon (IFN)-γ secretion, interleukin (IL)-2 production and splenocyte proliferation in response to anti-CD3⁺ CD28⁺ antibodies in mice. Furthermore, FTI-277 reduced spleen lymphocyte apoptosis in septic mice. Therefore, FTI-277 regulates spleen lymphocyte activity via the PD-L1 signalling pathway, with significant anti-inflammatory effects attributable to suppression of the NF-κB pathway. Farnesyltransferase represents a valuable therapeutic target for the treatment of sepsis.

Plague: history and contemporary analysis

Plague has caused ravaging outbreaks, including the Justinian plague and the "black death" in the Middle Ages. The causative agents of these outbreaks have been confirmed using modern molecular tests. The vector of plague during pandemics remains the subject of controversy. Nowadays, plague must be suspected in all areas where plague is endemic in rodents when patients present with adenitis or with pneumonia with a bloody expectorate. Diagnosis is more difficult in the situation of the reemergence of plague, as in Algeria for example, told by the first physician involved in that outbreak (NM). When in doubt, it is preferable to prescribe treatment with doxycycline while waiting for the test results because of the risk of fatality in individuals with plague. The typical bubo is a type of adenitis that is painful, red and nonfluctuating. The diagnosis is simple when microbiological analysis is conducted. Plague is a likely diagnosis when one sees gram-negative bacilli in lymph node aspirate or biopsy samples. Yersinia pestis grows very easily in blood cultures and is easy to identify by biochemical tests and MALDI-TOF mass spectrometry. Pneumonic plague and septicemic plague without adenitis are difficult to diagnose, and these diagnoses are often made by chance or retrospectively when cases are not part of an epidemic or related to another specific epidemiologic context. The treatment of plague must be based on gentamicin or doxycycline. Treatment with one of these antibiotics must be started as soon as plague is suspected. Analysis of past plague epidemics by using modern laboratory tools illustrated the value of epidemic buboes for the clinical diagnosis of plague; and brought new concepts regarding its transmission by human ectoparasites.

Do aspirin and statins prevent severe sepsis?

PURPOSE OF REVIEW

Sepsis is an inflammatory condition associated with significant morbidity and mortality. Given the lack of specific therapies for the condition, prevention has garnered significant interest and increased importance. The article reviews the current literature regarding the use of aspirin and statins for the prevention of sepsis.

RECENT FINDINGS

Aspirin and statins have been integral in the prevention of atherosclerotic disease. Additionally, statins have proven beneficial in the prevention of nonatherosclerotic conditions secondary to their pleiotropic effects. In animal models, this pleiotropism modulates many inflammatory pathways of sepsis. The platelet also plays an integral role in this inflammatory cascade of sepsis. Scientific data indicates that antiplatelet therapy, including aspirin, may attenuate these undesirable effects of platelets. Finally, observational studies have shown that patients taking statins have a decreased incidence of sepsis and septic shock, and aspirin may potentiate these benefits.

SUMMARY

Sepsis is a deadly and costly condition with no available, specific treatment options. The statins and aspirin are well tolerated and widely used for prevention of cardiovascular disease. Because of their effects on the immune system and inflammatory pathways, they may present viable medical options for the prevention of sepsis.

Farnesyltransferase inhibitor FTI-277 reduces mortality of septic mice along with improved bacterial clearance

Treatment with statins, inhibitors of HMG-CoA reductase, extends the survival of septic mice. However, the molecular mechanisms underlying the cholesterol-lowering, independent beneficial effects of statins in sepsis are poorly understood. The inhibition of protein isoprenylation, namely farnesylation and geranylgeranylation, has been proposed as a mediator of the pleiotropic protective effects of statins, although direct evidence is lacking. Major features of sepsis-induced immune suppression include T-cell dysfunction, which is characterized by apoptosis of splenic T cells, increased CD4(+)Foxp3(+) regulatory T cells (Tregs), and suppression of type 1 helper T-cell response [e.g., interferon-γ (IFN-γ) secretion] in mice. Here, we show that the induction of sepsis by cecal ligation and puncture (CLP) resulted in increases in farnesyltransferase activity and farnesylated proteins in the spleen relative to sham operation. Treatment with farnesyltransferase inhibitor N-[4-[2(R)-amino-3-mercaptopropyl]amino-2-phenylbenzoyl]methionine methyl ester trifluoroacetate salt (FTI-277) (25 mg/kg b.wt. i.p.) at 2 h after CLP blocked the increase in farnesylated proteins and improved survival and bacterial clearance of septic mice. FTI-277 reverted to or mitigated sepsis-induced apoptosis in spleen and thymus, increased splenic CD4(+)Foxp3(+) Tregs, and suppressed IFN-γ secretion and proliferation of splenocytes in response to anti-CD3+CD28 antibodies in mice. Moreover, FTI-277 promoted macrophage phagocytotic activity in septic mice. These results indicate that elevation in protein farnesylation plays a role in derangements in immune function and mortality of septic mice. These findings suggest that prevention of immune dysfunction might contribute to FTI-277-induced improvement in survival of septic mice. These data highlight protein farnesyltransferase as a novel potential molecular target to reduce the mortality of patients with sepsis.