Plasmodium Infection Promotes Genomic Instability and AID-Dependent B Cell Lymphoma.

Chronic infection with Plasmodium falciparum was epidemiologically associated with endemic Burkitt's lymphoma, a mature B cell cancer characterized by chromosome translocation between the c-myc oncogene and Igh, over 50 years ago. Whether infection promotes B cell lymphoma, and if so by which mechanism, remains unknown. To investigate the relationship between parasitic disease and lymphomagenesis, we used Plasmodium chabaudi (Pc) to produce chronic malaria infection in mice. Pc induces prolonged expansion of germinal centers (GCs), unique compartments in which B cells undergo rapid clonal expansion and express activation-induced cytidine deaminase (AID), a DNA mutator. GC B cells elicited during Pc infection suffer widespread DNA damage, leading to chromosome translocations. Although infection does not change the overall rate, it modifies lymphomagenesis to favor mature B cell lymphomas that are AID dependent and show chromosome translocations. Thus, malaria infection favors mature B cell cancers by eliciting protracted AID expression in GC B cells. PAPERCLIP.

Regulation of DNA end joining, resection, and immunoglobulin class switch recombination by 53BP1.

53BP1 is a DNA damage protein that forms phosphorylated H2AX (γ-H2AX) dependent foci in a 1 Mb region surrounding DNA double-strand breaks (DSBs). In addition, 53BP1 promotes genomic stability by regulating the metabolism of DNA ends. We have compared the joining rates of paired DSBs separated by 1.2 kb to 27 Mb on chromosome 12 in the presence or absence of 53BP1. 53BP1 facilitates joining of intrachromosomal DSBs but only at distances corresponding to γ-H2AX spreading. In contrast, DNA end protection by 53BP1 is distance independent. Furthermore, analysis of 53BP1 mutants shows that chromatin association, oligomerization, and N-terminal ATM phosphorylation are all required for DNA end protection and joining as measured by immunoglobulin class switch recombination. These data elucidate the molecular events that are required for 53BP1 to maintain genomic stability and point to a model wherein 53BP1 and H2AX cooperate to repress resection of DSBs.

Mitochondrial control of store-operated Ca2+ channels in cancer: Pharmacological implications.

Intracellular Ca2+ is a pleiotropic second messenger involved in control of different cell and physiological functions including long-term processes such as cell proliferation, migration and survival. Agonist-induced Ca2+ entry in most cells, especially in non-excitable cells including epithelial cells, is mediated by store-operated Ca2+ entry (SOCE), a Ca2+ entry pathway activated by agonist-induced release of Ca2+ from intracellular stores in the endoplasmic reticulum (ER). This pathway is modulated also by mitochondria which, acting as Ca2+ sinks, take up Ca2+, thus limiting Ca2+-dependent inactivation of Ca2+-release activated Ca2+ channels (CRAC). Compelling evidence shows that SOCE is upregulated in a large variety of cancer cells and this change contribute to cancer hallmarks. Mechanisms for enhanced SOCE include changes in expression of members of the Orai, Stromal interaction molecule (STIM) and canonical transient receptor potential channel (TRPc) gene families. Tumor cell mitochondria may contribute to SOCE upregulation in cancer as well. Molecular players involved in enhancing mitochondrial Ca2+ uptake are upregulated in tumor cells whereas negative modulators are repressed. Furthermore, mitochondrial potential, the driving force for mitochondrial Ca2+ uptake, is enhanced in tumor cells due to the Warburg effect. Finally, SOCE in tumor cells may be sustained further by the gain of function of non-selective TRPC channels permeable to Na+ that favour Ca2+ exit from mitochondria in exchange for Na+, thus limiting Ca2+-dependent inactivation of Orai1 channels. Therefore, tumor cell mitochondria may efficiently contribute to enhance and sustain SOCE in cancer. Interestingly, this effect could be counterbalanced by selected non-steroidal anti-inflammatory drugs (NSAIDs) reported to prevent colorectal cancer and other forms of cancer.

Silica-Calcium-Alginate Hydrogels for the Co-Immobilization of Glucose Oxidase and Catalase to Reduce the Glucose in Grape Must.

Higher temperatures due to climate change are causing greater sugar production in grapes and more alcoholic wines. The use of glucose oxidase (GOX) and catalase (CAT) in grape must is a biotechnological green strategy to produce reduced-alcohol wines. GOX and CAT were effectively co-immobilized by sol-gel entrapment in silica-calcium-alginate hydrogel capsules. The optimal co-immobilization conditions were achieved at a concentration of the colloidal silica, sodium silicate and sodium alginate of 7.38%, 0.49% and 1.51%, respectively, at pH 6.57. The formation of a porous silica-calcium-alginate structure was confirmed by environmental scanning electron microscopy and the elemental analysis of the hydrogel by X-ray spectroscopy. The immobilized GOX showed a Michaelis-Menten kinetic, while the immobilized CAT fits better to an allosteric model. Immobilization also conferred superior GOX activity at low pH and temperature. The capsules showed a good operational stability, as they could be reused for at least 8 cycles. A substantial reduction of 26.3 g/L of glucose was achieved with encapsulated enzymes, which corresponds to a decrease in potential alcoholic strength of must of about 1.5% vol. These results show that co-immobilized GOX and CAT in silica-calcium-alginate hydrogels is a promising strategy to produce reduced-alcohol wines.

Entrapment of Glucose Oxidase and Catalase in Silica-Calcium-Alginate Hydrogel Reduces the Release of Gluconic Acid in Must.

Glucose oxidase (GOX) and catalase (CAT) were co-immobilized in silica-calcium-alginate hydrogels to degrade must glucose. The effect of the enzyme dose (1.2-2.4 U/mL), the initial must pH (3.6-4.0), and the incubation temperature (10-20 °C) on the glucose consumption, gluconic acid concentration, pH, and color intensity of Verdejo must was studied by using a Box-Behnken experimental design and comparing free and co-immobilized enzymes. A reduction of up to 37.3 g/L of glucose was observed in co-immobilized enzyme-treated must, corresponding to a decrease in its potential alcohol strength of 2.0% vol. (v/v), while achieving a slight decrease in its pH (between 0.28 and 0.60). This slight acidification was due to a significant reduction in the estimated gluconic acid found in the must (up to 73.7%), likely due to its accumulation inside the capsules. Regarding the operational stability of immobilized enzymes, a gradual reduction in glucose consumption was observed over eight consecutive cycles. Finally, co-immobilized enzymes showed enhanced efficiency over a reaction period of 48 h, with an 87.1% higher ratio of glucose consumed per enzyme dose in the second 24 h period compared with free enzymes. These findings provide valuable insights into the performance of GOX-CAT co-immobilized to produce reduced-alcohol wines, mitigating excessive must acidification.

Fate mapping for activation-induced cytidine deaminase (AID) marks non-lymphoid cells during mouse development.

The Aicda gene encodes Activation-Induced cytidine Deaminase (AID), an enzyme essential for remodeling antibody genes in mature B lymphocytes. AID is also responsible for DNA damage at oncogenes, leading to their mutation and cancer-associated chromosome translocation in lymphoma. We used fate mapping and AID(GFP) reporter mice to determine if AID expression in the mouse extends beyond lymphocytes. We discovered that AID(cre) tags a small fraction of non-lymphoid cells starting at 10.5 days post conception (dpc), and that AID(GFP+) cells are detectable at dpc 11.5 and 12.5. Embryonic cells are tagged by AID(cre) in the submandibular region, where conditional deletion of the tumor suppressor PTEN causes squamous papillomas. AID(cre) also tags non-lymphoid cells in the embryonic central nervous system. Finally, in the adult mouse brain, AID(cre) marks a small fraction of diverse neurons and distinct neuronal populations, including pyramidal cells in cortical layer IV.

Inflammatory Flt3l is essential to mobilize dendritic cells and for T cell responses during Plasmodium infection.

Innate sensing mechanisms trigger a variety of humoral and cellular events that are essential to adaptive immune responses. Here we describe an innate sensing pathway triggered by Plasmodium infection that regulates dendritic cell homeostasis and adaptive immunity through Flt3 ligand (Flt3l) release. Plasmodium-induced Flt3l release in mice requires Toll-like receptor (TLR) activation and type I interferon (IFN) production. We found that type I IFN supports the upregulation of xanthine dehydrogenase, which metabolizes the xanthine accumulating in infected erythrocytes to uric acid. Uric acid crystals trigger mast cells to release soluble Flt3l from a pre-synthesized membrane-associated precursor. During infection, Flt3l preferentially stimulates expansion of the CD8-α(+) dendritic cell subset or its BDCA3(+) human dendritic cell equivalent and has a substantial impact on the magnitude of T cell activation, mostly in the CD8(+) compartment. Our findings highlight a new mechanism that regulates dendritic cell homeostasis and T cell responses to infection.