Prophage terminase with tRNase activity sensitizes Salmonella enterica to oxidative stress

Phage viruses shape the evolution and virulence of their bacterial hosts. The Salmonella enterica genome encodes several stress-inducible prophages. The Gifsy-1 prophage terminase protein, whose canonical function is to process phage DNA for packaging in the virus head, unexpectedly acts as a transfer ribonuclease (tRNase) under oxidative stress, cleaving the anticodon loop of tRNALeu. The ensuing RNA fragmentation compromises bacterial translation, intracellular survival, and recovery from oxidative stress in the vertebrate host. S. enterica adapts to this transfer RNA (tRNA) fragmentation by transcribing the RNA repair Rtc system. The counterintuitive translational arrest provided by tRNA cleavage may subvert prophage mobilization and give the host an opportunity for repair as a way of maintaining bacterial genome integrity and ultimately survival in animals.

Anaerobic respiration of host-derived methionine sulfoxide protects intracellular Salmonella from the phagocyte NADPH oxidase

Intracellular Salmonella experiencing oxidative stress downregulates aerobic respiration. To maintain cellular energetics during periods of oxidative stress, intracellular Salmonella must utilize terminal electron acceptors of lower energetic value than molecular oxygen. We show here that intracellular Salmonella undergoes anaerobic respiration during adaptation to the respiratory burst of the phagocyte NADPH oxidase in macrophages and in mice. Reactive oxygen species generated by phagocytes oxidize methionine, generating methionine sulfoxide. Anaerobic Salmonella uses the molybdenum cofactor-containing DmsABC enzymatic complex to reduce methionine sulfoxide. The enzymatic activity of the methionine sulfoxide reductase DmsABC helps Salmonella maintain an alkaline cytoplasm that supports the synthesis of the antioxidant hydrogen sulfide via cysteine desulfuration while providing a source of methionine and fostering redox balancing by associated dehydrogenases. Our investigations demonstrate that nontyphoidal Salmonella responding to oxidative stress exploits the anaerobic metabolism associated with dmsABC gene products, a pathway that has accrued inactivating mutations in human-adapted typhoidal serovars.

Gre factors help Salmonella adapt to oxidative stress by improving transcription elongation and fidelity of metabolic genes

Detoxification, scavenging, and repair systems embody the archetypical antioxidant defenses of prokaryotic and eukaryotic cells. Metabolic rewiring also aids with the adaptation of bacteria to oxidative stress. Evolutionarily diverse bacteria combat the toxicity of reactive oxygen species (ROS) by actively engaging the stringent response, a stress program that controls many metabolic pathways at the level of transcription initiation via guanosine tetraphosphate and the α-helical DksA protein. Studies herein with Salmonella demonstrate that the interactions of structurally related, but functionally unique, α-helical Gre factors with the secondary channel of RNA polymerase elicit the expression of metabolic signatures that are associated with resistance to oxidative killing. Gre proteins both improve transcriptional fidelity of metabolic genes and resolve pauses in ternary elongation complexes of Embden-Meyerhof-Parnas (EMP) glycolysis and aerobic respiration genes. The Gre-directed utilization of glucose in overflow and aerobic metabolism satisfies the energetic and redox demands of Salmonella, while preventing the occurrence of amino acid bradytrophies. The resolution of transcriptional pauses in EMP glycolysis and aerobic respiration genes by Gre factors safeguards Salmonella from the cytotoxicity of phagocyte NADPH oxidase in the innate host response. In particular, the activation of cytochrome bd protects Salmonella from phagocyte NADPH oxidase-dependent killing by promoting glucose utilization, redox balancing, and energy production. Control of transcription fidelity and elongation by Gre factors represent important points in the regulation of metabolic programs supporting bacterial pathogenesis.

Instantaneous activation energy of alkali activated materials

Alkali activated materials (AAM) are generally cured at high temperatures to compensate for the low reaction rate. Higher temperature accelerates the reaction of AAM as in cement-based materials and this effect is generally predicted using Arrhenius equation based on the activation energy. While apparent activation energy is calculated from parallel isothermal calorimetry measurements at different temperatures, instantaneous activation energy is typically measured using a differential scanning calorimeter. Compared to the apparent activation energy, instantaneous activation energy has minimal effects on the microstructural changes due to the variation in temperature. In this work, the evolution of activation energy was determined by traditional methods and was compared with the instantaneous activation energy. It was found that while the activation energy changed with the progress of reaction over traditional methods, the instantaneous activation energy did not show any changes / or remained the same. The instantaneous activation energy was also found to be higher compared to the apparent activation energy determined with traditional methods.

Is there a positive effect of participation on a clinical trial for patients with advanced non-small cell lung cancer?

BACKGROUND

There is general belief that patients who enrolled on a clinical trial have better outcomes compared to those who are treated outside of a trial. We analyzed if there was a 'trial effect' for patients with advanced non-small cell lung cancer (NSCLC) treated with chemotherapy.

MATERIALS AND METHODS

A retrospective analysis of cohorts of patients with advanced NSCLC who received chemotherapy inside and outside of a clinical trial were analyzed for response rates (RR), progression free survival (PFS), overall survival (OS), 1 and 2 year survival.

RESULTS

There were 194 patients who received chemotherapy of which, 54 were on a clinical trial and 140 outside of it. For the whole group, the RR, median PFS, OS, one and two-year survivals were 35.4%, six months (range, 2-70), seven months (range, 2-72), 29.8% and 9.7% respectively. The differences in RR and PFS of patients who were treated inside and outside of a clinical trial were not significant (P=0.6164, 0.0881). The differences in median OS and one-year survivals between the groups were significant (P=0.0052, 0.022). For the whole group, patients who received II line chemotherapy had better OS (P< or = 0.0001). More patients in the trial group received II line chemotherapy (P=0.0004).The difference in the median OS between the groups continued to be significant even after patients who received II line chemotherapy were censored (P=0.0437).

CONCLUSION

Patients with advanced NSCLC who were treated inside of a clinical trial had better OS compared to those who were treated outside of it.

A retrospective analysis of epidemiology and treatment patterns for gastric cancer at a tertiary health care center in India

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Background: Gastric cancer is the second most common gastrointestinal cancer in our hospital based cancer registry. This retrospective analysis aims at studying the epidemiology and treatment patterns for gastric cancer at our hospital, which is a tertiary care cancer center for the state of Andhra Pradesh in south India. Methods: A retrospective analysis of the case records of 125 consecutive patients with gastric cancer who presented to our department between Jan 2004 and Dec 2005 were analysed. Data regarding epidemiology, stages at diagnosis and treatment plans were collected. Patients with early gastric cancer received 5FU based chemoradiation or chemotherapy only. Palliative chemotherapy included 5FU/cisplatin based regimens. Results: A total of 125 patients were analysed. The median age was 61years (range 18–82 years). 71% were males and 29% females. Being a tertiary care center, 92% were referred with a confirmed diagnosis on endoscopic biopsy. 30% were smokers, 11% consumed alcohol, 40% had both habits while 29% had neither. The most common part of the stomach involved was the antro-pyloric region (44%) followed by the body (30%), GE junction/cardia (20%) while 6% had diffuse involvement including linitis plastica. At diagnosis, 35% were early stage, 56% metastatic and 8% locally advanced tumors. 90% patients who had surgery for early stage disease had T2,3 tumors. One third had inadequate nodal staging.70% of patients who had curative resections underwent adjuvant chemoradiation and 30% had chemotherapy only. Of all patients with metastatic disease, 65% palliative chemotherapy while 45% opted for best supportive care. Conclusions: The distribution of tumors within the stomach is similar to Japanese data, which may reflect the common etiological factors like high salt diet. The fact that one third of patients had inadequate nodal dissection stresses the relevance of adjuvant chamoradiotherapy protocols. The high incidence of smoking as a contributory factor in the etiology reflects the need for aggressive anti tobacco legislation. The study reiterates the need for inexpensive and novel therapies for palliation of symptoms in patients with advanced disease and widens the scope for collaborative clinical trials.

No significant financial relationships to disclose.