Based on the role of phosphorylation of the histone H2A variant H2AX in recruitment of DNA repair and checkpoint proteins to the sites of DNA damage, we have investigated ␥H2AX as a reporter of tumor radiosensitivity and a potential target to enhance the effectiveness of radiation therapy. Clinically relevant ionizing radiation (IR) doses induced similar patterns of ␥H2AX focus formation or immunoreactivity in radiosensitive and radioresistant human tumor cell lines and xenografted tumors. However, radiosensitive tumor cells and xenografts retained ␥H2AX for a greater duration than radioresistant cells and tumors. These results suggest that persistence of ␥H2AX after IR may predict tumor response to radiotherapy. We synthesized peptide mimics of the H2AX carboxyl-terminal tail to test whether antagonizing H2AX function affects tumor cell survival following IR. The peptides did not alter the viability of unirradiated tumor cells, but both blocked induction of ␥H2AX foci by IR and enhanced cell death in irradiated radioresistant tumor cells. These results suggest that H2AX is a potential molecular target to enhance the effects of radiotherapy.

The cellular response to ionizing radiation includes induction of the early growth response 1 gene (EGRI). The present work has examined the involvement of reactive oxygen intermediates (ROTs) in this response. Exposure of human HL-525 cells, an HL-60 subclone deficient in protein kinase C-mediated signaling, to both ionizing radiation and H202 was associated with increases in EGR-1 transcripts. These increases in EGR-1 expression were inhibited by the antioxidant N-acetyl-L-cysteine (NAC). Nuclear run-on assays demonstrate that NAC inhibits the activation of EGRI transcription by these agents. Previous studies have shown that induction ofEGRI by x-rays is conferred by serum response or CC(A/T)6GG (CArG) elements. The present studies demonstrate similar findings with H202 and the finding that activation of the EGRI promoter region containing CArG elements is abrogated by NAC. Moreover, we show that NAC inhibits the ability of a single CArG box to confer x-ray and H202 inducibility when linked to a heterologous promoter. Taken together, these fmdings indicate that ROIs induce EGRI transcription by activation of CArG elements.

Antimicrobial resistance (AMR) continues to pose a significant public health problem in terms of mortality and economic loss. Health authorities of several countries including India have formulated action plans for its containment. In this fight against AMR, it is important to realize the contribution by all the following four spheres: humans, animals, food and environment. This review incorporates all the spheres of One Health concept from the Indian perspective. India has one of the highest rates of resistance to antimicrobial agents used both in humans and food animals. The environment, especially the water bodies, have also reported the presence of resistant organisms or their genes. Specific socio-economic and cultural factors prevalent in India make the containment of resistance more challenging. Injudicious use of antimicrobials and inadequate treatment of waste waters are important drivers of AMR in India. Use of sludge in agriculture, improper discard of livestock animals and aquaculture industry are considered AMR contributors in other countries but Indian data regarding these are lacking. Efforts to combat AMR have been initiated by the Indian health authorities but are still at preliminary stages. Keeping in view the challenges unique to India, future directions are proposed.

Shigella species represent one of the growing numbers of antimicrobial-resistant bacteria in developing countries. Fluoroquinolone-resistant strains of Shigella dysenteriae type1 and Shigella flexneri type 2a emerged in India during 2002 and 2003, respectively. Sixty strains of Shigella from different parts of India were analysed for antimicrobial susceptibility, the presence of the qnr plasmid, mutations in the quinolone resistance determining regions (QRDRs), fluoroquinolone accumulation, and the presence of other genes encoding resistance to various antimicrobials. Fluoroquinolone-resistant strains had mutations in gyrA and parC genes and had an active efflux system. They were also resistant to several other antimicrobials but were susceptible to azithromycin and ceftriaxone. The majority of the strains harboured genes encoding resistance to ampicillin (97 %), tetracycline (95 %), streptomycin (95 %) and chloramphenicol (94 %). PFGE analysis revealed clonality among strains of S. dysenteriae types 1 and 5, S. flexneri type 2a and Shigella boydii type 12. INTRODUCTIONShigellosis remains an important public health problem in developing countries with Shigella sonnei in Europe and the US and Shigella flexneri in Asian and African countries being of epidemiological importance. Antimicrobial therapy is advocated for shigellosis to shorten the duration of illness (Salam & Bennish, 1991). However, in Asia and Africa, antimicrobial resistance is an emerging problem among Shigella species (von Seidlein et al., 2006) and treatment options are becoming limited globally (Salam & Bennish, 1991;Kariuki & Hart, 2001). The World Health Organization has recommended that ciprofloxacin should be considered a first-line antibiotic for the treatment of shigellosis, and the use of nalidixic acid is not encouraged, even in areas where it is still effective against Shigella (WHO, 2004). Similar to the prevalence of different serotypes, antimicrobial-resistance patterns of strains also differ from country to country and even within the same country (Pazhani et al., 2005;von Seidlein et al., 2006), which may be due to the spread of resistant clones as found for multidrug-resistant strains of Shigella dysenteriae type 1 in eastern parts of India (Pazhani et al., 2004). In this study, we have investigated the mechanisms of antibiotic resistance and clonal relatedness of Shigella strains isolated from epidemic and endemic cases of shigellosis in different parts of India. METHODSBacterial strains. We examined 60 strains of Shigella species (20 S. dysenteriae, 16 S. flexneri, 7 Shigella boydii and 17 S. sonnei) isolated from dysentery outbreaks from different parts of India and sporadic hospitalized cases of shigellosis in Kolkata and Goa between 2001 and 2004. Strains were confirmed as Shigella spp. by standard biochemical tests (WHO, 1987) and serotyped using commercially available antisera (Denka Seiken).Antimicrobial susceptibility testing. Antimicrobial susceptibility tests were performed by a disc diffusion method in accordance with...

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Shigellosis is one of the major causes of diarrhoea in India. The accurate estimates of morbidity and mortality due to shigellosis are lacking, though it is endemic in the country and has been reported to cause many outbreaks. The limited information available indicates Shigella to be an important food-borne pathogen in India. S. flexneri is the most common species, S. sonnei and non-agglutinable shigellae seem to be steadily surfacing, while S. dysenteriae has temporarily disappeared from the northern and eastern regions. Antibiotic-resistant strains of different Shigella species and serotypes have emerged all over the world. Especially important is the global emergence of multidrug resistant shigellae, notably the increasing resistance to third generation cephalosporins and fluoroquinolones, and also azithromycin. This calls for a continuous and strong surveillance of antibiotic resistance across the country for periodic updation of the local antibiograms. The prevention of shigellosis is desirable as it will substantially reduce the morbidity associated with diarrhoea in the country. Public health measures like provision of safe water and adequate sanitation are of immense importance to reduce the burden of shigellosis, however, the provision of resources to develop such an infrastructure in India is a complex issue and will take time to resolve. Thus, the scientific thrust should be focused towards development of a safe and affordable multivalent vaccine. This review is focused upon the epidemiology, disease burden and the therapeutic challenges of shigellosis in Indian perspective.

To investigate the role of CD4 and CD8 T cells in arthritis, we generated transgenic mice deficient in CD4 and CD8 molecules expressing RA-susceptible gene HLA-DQ8. DQ8.CD4(-/-) mice were resistant to developing collagen-induced arthritis (CIA). However, DQ8.CD8(-/-) mice developed CIA with increased incidence and more severity than DQ8 mice. Both DQ8.CD8(-/-) and DQ8 mice produced rheumatoid factor. In addition, DQ8.CD8(-/-) mice produced antinuclear Abs. The B cell compartment and expression of DQ8 were normal in all the strains, although frequency of cells expressing DQ8 was less in CD4(-/-) mice. An increased frequency of CD3(+) double-negative (DN) T cells was found in DQ8.CD8(-/-) compared with DQ8.CD4(-/-) and DQ8 mice. These CD3(+) DN T cells produced high amounts of IL-10 in CD8-deficient mice. Analysis of cell division using a cell cycle tracking dye showed a higher rate of division of CD3(+) and CD3(+) DN T cells in DQ8.CD8(-/-) mice compared with DQ8.CD4(-/-) and DQ8 mice. Decreased apoptosis was seen in CIA-susceptible DQ8 and CD8-deficient mice, indicating a defect in activation-induced cell death. These observations suggest that CD4 cells are necessary for initiation of CIA in DQ8 mice. We hypothesize that CD8(+) T cells are not capable of initiating CIA in DQ8-transgenic mice but may have a regulatory/protective effect.

The stress-activated protein (SAP) kinases are induced by tumor necrosis factor, oncoproteins, and UV light. The present studies demonstrate that ionizing radiation (IR) activates p54 SAP kinase. IR-induced activation of SAP kinase is associated with binding to the SH2/SH3-containing adaptor protein Grb2. This interaction is mediated by the SH3 domains of Grb2 and the proline-rich sequence PPPKIP in the carboxy-terminal region of SAP kinase. We also demonstrated that SAP kinase and the p85 alpha-subunit of phosphatidylinositol (PI) 3-kinase form a complex in irradiated cells. The results indicate that this complex involves binding of the p85 alpha subunit of PI 3-kinase to the SH2 domain of Grb2. The functional role of linking SAP kinase to PI 3-kinase is further supported by the finding that wortmannin, an inhibitor of PI 3-kinase, stimulates SAP kinase activity. These results suggest that the cellular response to IR may include regulation of SAP kinase by a PI 3-kinase-dependent signaling pathway.