Small organic molecules accelerate the expansion of regulatory T cells.

The regulatory T cells (Treg cells) expressing CD4 + CD25 + FOXP3 + markers are indispensable for the initiation of immune homeostasis and tolerance to self-antigens in both mice and humans. A decrease in regulatory T cells leads to various autoimmune pathologies. Herein, we report three low molecular weight, small organic molecules as a new series of Treg proliferators TRP-1-3. These small molecules were tested for their proliferative effect on regulatory T cells. It was found that TRP-1 (Oleracein E) strongly accelerates the Treg proliferation in vitro in a concentration-dependent manner. The effect was evident for all subsets of Treg cells tested, including naturally occurring, thymus-derived and peripherally-induced or adaptive Treg, indicating an effect independent of the maturation site. Importantly, increased Treg cells numbers by TRP-1 correlated with improved CD4 + CD25 + FOXP3 + expression in vitro, while propidium iodide-based staining showed low TRP-1-induced cytotoxicity. Molecular docking plus simulation studies of these TRP-1-3 with IL-2R, mTOR and TCR receptors suggest a TCR-based Treg cells activation mechanism. Because of its high Treg cells activities and low cellular cytotoxicity, TRP-1-3 may be useful in stimulating ex-vivo/in-vivo, Treg cell-specific responses for therapeutic applications.

Potential anti-proliferative effects of chemical constituents and hemisynthetic derivatives from Scadoxus pseudocaulus (Amarillydaceae).

BACKGROUND: Biological significance of Amaryllidaceae is well advocated from the literature. In Cameroon, plants from this family are routinely used for the cure of liver, cancer and cardiovascular diseases. To date, no scientific investigation corresponding to the anti-cancer activity of extracts and isolated compounds of Scadoxus pseudocaulus is available. OBJECTIVE: Current study is focused to elaborate the anti-proliferative effects of natural isolates (compounds 1-6, 9) and hemi-synthetic analogs (compounds 7-8) extracted from S. pseudocaulu. METHODS: Column chromatography of the ethyl acetate extract followed by purification of different fractions led to the isolation of seven compounds (1 - 6, 9). Esterification reaction of compound 6 was carried out using butyroyl chlorides and triethylamin to produce two derivatives (7 - 8). The cytotoxic activity was performed after staining of treated cells with florescent dye propidium iodide. Dead cells were detected using cytometer FL2 or FL3 channels/filters. RESULTS: Trans-derivative of narciclasine (a natural isolate from S. pseudocaulus), was found to be most potent among all tested compounds. Its effects were more significant on low malignant follicular lymphoma (DoHH2 cells) as compared to highly malignant (EBV infected) Burkitts lymphoma (Raji cells). CONCLUSION: From our results, narciclasine appears to hold the potential of a lead molecule that can be used to bridge the therapeutic gaps in cancer research.

Comparison of mitochondrial gene expression and polysome loading in different tobacco tissues.

BACKGROUND: To investigate translational regulation of gene expression in plant mitochondria, a mitochondrial polysome isolation protocol was established for tobacco to investigate polysomal mRNA loading as a proxy for translational activity. Furthermore, we developed an oligonucleotide based microarray platform to determine the level of Nicotiana tabacum and Arabidopsis thaliana mitochondrial mRNA. RESULTS: Microarray analysis of free and polysomal mRNAs was used to characterize differences in the levels of free transcripts and ribosome-bound mRNAs in various organs of tobacco plants. We have observed higher mitochondrial transcript levels in young leaves, flowers and floral buds as compared to fully expanded leaves and roots. A similar pattern of abundance was observed for ribosome-bound mitochondrial mRNAs in these tissues. However, the accumulation of the mitochondrial protein COX2 was found to be inversely related to that of its ribosome-bound mRNA. CONCLUSIONS: Our results indicate that the association of mitochondrial mRNAs to ribosomes is largely determined by the total transcript level of a gene. However, at least for Cox2, we demonstrated that the level of ribosome-bound mRNA is not reflected by the amount of COX2 protein.

Mechanistic understanding and significance of small peptides interaction with MHC class II molecules for therapeutic applications.

Major histocompatibility complex (MHC) class II molecules are expressed by antigen-presenting cells and stimulate CD4(+) T cells, which initiate humoral immune responses. Over the past decade, interest has developed to therapeutically impact the peptides to be exposed to CD4(+) T cells. Structurally diverse small molecules have been discovered that act on the endogenous peptide exchanger HLA-DM by different mechanisms. Exogenously delivered peptides are highly susceptible to proteolytic cleavage in vivo; however, it is only when successfully incorporated into stable MHC II-peptide complexes that these peptides can induce an immune response. Many of the small molecules so far discovered have highlighted the molecular interactions mediating the formation of MHC II-peptide complexes. As potential drugs, these small molecules open new therapeutic approaches to modulate MHC II antigen presentation pathways and influence the quality and specificity of immune responses. This review briefly introduces how CD4(+) T cells recognize antigen when displayed by MHC class II molecules, as well as MHC class II-peptide-loading pathways, structural basis of peptide binding and stabilization of the peptide-MHC complexes. We discuss the concept of MHC-loading enhancers, how they could modulate immune responses and how these molecules have been identified. Finally, we suggest mechanisms whereby MHC-loading enhancers could act upon MHC class II molecules.

Hypoxia up-regulates mitochondrial genome-encoded transcripts in Arabidopsis roots.

Plants are frequently exposed to limitations in oxygen availability during their lifetime. During evolution, they have developed a number of physiological and morphological adaptations to tolerate oxygen and other stress conditions. These include regulation of growth by gene expression and ATP generation. The regulation of nuclear genes after hypoxia and anoxia is well studied; however, the regulation of mitochondrial genes in response to oxygen stress has not been characterized to date. Therefore, we have established an Arabidopsis mitochondrial genome-specific microarray that accommodates probes for all mitochondrial DNA-encoded genes and conserved open reading frames. Our analysis showed an up-regulation of mitochondrial transcripts in Arabidopsis roots after 48 h of hypoxia. Since no significant difference was detected in the expression of mitochondrial RNA polymerases or the mitochondrial DNA content per cell, we propose a transcriptional mode of induction of mitochondrial gene expression under hypoxia.

Analysis of alanine aminotransferase in various organs of soybean (Glycine max) and in dependence of different nitrogen fertilisers during hypoxic stress.

Alanine aminotransferase (AlaAT) catalyses the reversible conversion of pyruvate and glutamate into alanine and oxoglutarate. In soybean, two subclasses were identified, each represented by two highly similar members. To investigate the role of AlaAT during hypoxic stress in soybean, changes in transcript level of both subclasses were analysed together with the enzyme activity and alanine content of the tissue. Moreover, the dependency of AlaAT activity and gene expression was investigated in relation to the source of nitrogen supplied to the plants. Using semi-quantitative PCR, GmAlaAT genes were determined to be highest expressed in roots and nodules. Under normal growth conditions, enzyme activity of AlaAT was detected in all organs tested, with lowest activity in the roots. Upon waterlogging-induced hypoxia, AlaAT activity increased strongly. Concomitantly, alanine accumulated. During re-oxygenation, AlaAT activity remained high, but the transcript level and the alanine content decreased. Our results show a role for AlaAT in the catabolism of alanine during the initial period of re-oxygenation following hypoxia. GmAlaAT also responded to nitrogen availability in the solution during waterlogging. Ammonium as nitrogen source induced both gene expression and enzyme activity of AlaAT more than when nitrate was supplied in the nutrient solution. The work presented here indicates that AlaAT might not only be important during hypoxia, but also during the recovery phase after waterlogging, when oxygen is available to the tissue again.