Cellular conditioning with trichostatin A enhances the anti-stress response through up-regulation of HDAC4 and down-regulation of the IGF/Akt pathway

Evidence is accumulating that chromatin plays a major role in the control of cellular response to stress. This is best illustrated by the recent findings that chromatin-modifying factors of class III histone deacetylases (sirtuins) are capable of protecting cells from oxidative and genotoxic stress. In particular, Sirt1 has been shown to mimic the action of caloric restriction for the prevention of aging-associated diseases. In the present study, we have investigated the potential role of class I and II histone deacetylases (HDACs) in cellular protection against various stresses, including those caused by nutrient deprivation. For this, we utilized a cellular model in which expression of class I and II HDACs was altered as a result of cellular adaptation to trichostatin A (TSA), a selective inhibitor of these deacetylases. Our results indicated that TSA-resistant cells also developed resistance to H₂O₂, DNA-damaging agents, and to nutrient deprivation. Interestingly, the insulin signaling pathway mediated by Akt was inhibited in the TSA-resistant cells, mirroring the effect of glucose deprivation on this pathway. Since expression of HDAC4 was consistently enhanced in the TSA-resistant cell lines, we suggest that this enzyme may contribute to their anti-stress response. In agreement with this, siRNA-mediated knockdown of HDAC4 in stress-resistant cells enhanced their sensitivity to the DNA-damaging drug doxorubicin and also to glucose deprivation. Akt phosphorylation was also up-regulated in response to HDC4 knockdown. Together, these findings suggest that cellular conditioning with TSA may represent a useful approach to mimic the effects of caloric restriction.     

Accuracy of touch imprint cytology in diagnosing lung cancer.

A 3-year study assessed the diagnostic accuracy of touch imprint smears in the diagnosis of lung cancer. Touch imprint smears were prepared from 90 computerized tomographic-guided core needle lung biopsies. Cytological diagnosis of touch imprint smears were correlated with the histological diagnosis of the corresponding core needle biopsy specimen, which was taken as the gold standard. The sensitivity, specificity, positive predictive value and negative predictive value of imprint smear results were 89%, 100%, 100% and 68%, respectively. There were no false positives, and all patients with small cell lung cancer were correctly diagnosed with this technique. Imprint cytology can be used to provide a rapid, preliminary diagnosis of lung cancer.     

A spontaneous mutation of the rat Themis gene leads to impaired function of regulatory T cells linked to inflammatory bowel disease

Spontaneous or chemically induced germline mutations, which lead to Mendelian phenotypes, are powerful tools to discover new genes and their functions. Here, we report an autosomal recessive mutation that occurred spontaneously in a Brown-Norway (BN) rat colony and was identified as causing marked T cell lymphopenia. This mutation was stabilized in a new rat strain, named BN(m) for "BN mutated." In BN(m) rats, we found that the T cell lymphopenia originated in the thymus, was intrinsic to CD4 T lymphocytes, and was associated with the development of an inflammatory bowel disease. Furthermore, we demonstrate that the suppressive activity of both peripheral and thymic CD4(+) CD25(bright) regulatory T cells (Treg) is defective in BN(m) rats. Complementation of mutant animals with BN Treg decreases disease incidence and severity, thus suggesting that the impaired Treg function is involved in the development of inflammatory bowel disease in BN(m) rats. Moreover, the cytokine profile of effector CD4 T cells is skewed toward Th2 and Th17 phenotypes in BN(m) rats. Linkage analysis and genetic dissection of the CD4 T cell lymphopenia in rats issued from BN(m)×DA crosses allowed the localization of the mutation on chromosome 1, within a 1.5 megabase interval. Gene expression and sequencing studies identified a frameshift mutation caused by a four-nucleotide insertion in the Themis gene, leading to its disruption. This result is the first to link Themis to the suppressive function of Treg and to suggest that, in Themis-deficient animals, defect of this function is involved in intestinal inflammation. Thus, this study highlights the importance of Themis as a new target gene that could participate in the pathogenesis of immune diseases characterized by chronic inflammation resulting from a defect in the Treg compartment.     

Mutagenic and membranal effect of a phytotoxic molecule isolated from olive leaves parasitized by the fungusCycloconium oleaginum Cast

A phytotoxic substance (C₂₃H₄₄O₃) which is named Substance A, was purified from olive leaves infected withCycloconium oleaginum Cast. The mutagenic effect of this substance was detected using TA 100 and TA 102 strains ofSalmonella in the Ames test usingBacillus subtilis strains M45 rec^–, H17 rec⁺ in the rec assay. Another substance manifesting the mutagenic effect was found in the extract from theCycloconium oleaginum culture. This substance was not detected in the extract from contaminated olive leaves. Substance A increased electrolytes leakage from tissue of olive leaves, thus manifesting its phytotoxicity.     

LF 15-0195 treatment protects against central nervous system autoimmunity by favoring the development of Foxp3-expressing regulatory CD4 T cells

Experimental autoimmune encephalomyelitis (EAE) is an instructive model for the human demyelinating disease multiple sclerosis. Lewis (LEW) rats immunized with myelin-basic protein (MBP) develop EAE characterized by a single episode of paralysis, from which they recover spontaneously and become refractory to a second induction of disease. LF 15-0195 is a novel molecule that has potent immunosuppressive effects in several immune-mediated pathological manifestations, including EAE. In the present study, we show that a 30-day course of LF 15-0195 treatment not only prevents MBP-immunized LEW rats from developing EAE but also preserves their refractory phase to reinduction of disease. This effect is Ag driven since it requires priming by the autoantigen during the drug administration. In contrast to other immunosuppressive drugs, short-term treatment with this drug induces a persistent tolerance with no rebound of EAE up to 4 mo after treatment withdrawal. This beneficial effect of LF 15-0195 on EAE does not result from the deletion of MBP-specific Vbeta8.2 encephalitogenic T cells. In contrast, this drug favors the differentiation of MBP-specific CD4 T cells into Foxp3-expressing regulatory T cells that, upon adoptive transfer in syngeneic recipients, prevent the development of actively induced EAE. Finally, we demonstrate that the tolerance induced by LF 15-0195 treatment is not dependent on the presence of TGF-beta. Together, these data demonstrate that short-term treatment with LF 15-0195 prevents MBP-immunized LEW rats from EAE by favoring the development of Foxp-3-expressing regulatory CD4 T cells.