Mitochondrial dynamics and autophagy aid in removal of persistent mitochondrial DNA damage in Caenorhabditis elegans

Mitochondria lack the ability to repair certain helix-distorting lesions that are induced at high levels in mitochondrial DNA (mtDNA) by important environmental genotoxins and endogenous metabolites. These lesions are irreparable and persistent in the short term, but their long-term fate is unknown. We report that removal of such mtDNA damage is detectable by 48 h in Caenorhabditis elegans, and requires mitochondrial fusion, fission and autophagy, providing genetic evidence for a novel mtDNA damage removal pathway. Furthermore, mutations in genes involved in these processes as well as pharmacological inhibition of autophagy exacerbated mtDNA damage-mediated larval arrest, illustrating the in vivo relevance of removal of persistent mtDNA damage. Mutations in genes in these pathways exist in the human population, demonstrating the potential for important gene-environment interactions affecting mitochondrial health after genotoxin exposure.     

Effects of heat acclimatisation on work tolerance and thermoregulation in trained tropical natives

This study aimed to investigate the effects of heat acclimatisation on thermoregulatory responses and work tolerance in trained individuals residing in the tropics. Eighteen male trained soldiers, who are native to a warm and humid climate, performed a total of four heat stress tests donning the Skeletal Battle Order (SBO, 20.5 kg) and Full Battle Order (FBO, 24.7 kg) before (PRE) and after (POST) a 10-day heat acclimatisation programme. The trials were conducted in an environmental chamber (dry bulb temperature: 32 °C, relative humidity: 70%, solar radiation: 400 W/m²). Excluding the data sets of which participants fully completed the heat stress tests (210 min) before and after heat acclimatisation, work tolerance was improved from 173±30 to 201±18 min (∼21%, p<0.05, n=9) following heat acclimatisation. Following heat acclimatisation, chest skin temperature during exercise was lowered in SBO (PRE=36.7±0.3 vs. POST=36.5±0.3 °C, p<0.01) and FBO (PRE=36.8±0.4 vs. POST=36.6±0.3 °C, p<0.01). Ratings of perceived exertion were decreased with SBO and FBO (PRE=11±2; POST=10±2; p<0.05) after heat acclimatisation. Heat acclimatisation had no effects on baseline body core temperature, heart rate and sweat rate across trials (p>0.05). A heat acclimatisation programme improves work tolerance with minimal effects on thermoregulation in trained tropical natives.     

Exploiting antitumor immunity to overcome relapse and improve remission duration

Cancer survivors often relapse due to evolving drug-resistant clones and repopulating tumor stem cells. Our preclinical study demonstrated that terminal cancer patient's lymphocytes can be converted from tolerant bystanders in vivo into effective cytotoxic T-lymphocytes in vitro killing patient's own tumor cells containing drug-resistant clones and tumor stem cells. We designed a clinical trial combining peginterferon α-2b with imatinib for treatment of stage III/IV gastrointestinal stromal tumor (GIST) with the rational that peginterferon α-2b serves as danger signals to promote antitumor immunity while imatinib's effective tumor killing undermines tumor-induced tolerance and supply tumor-specific antigens in vivo without leukopenia, thus allowing for proper dendritic cell and cytotoxic T-lymphocyte differentiation toward Th1 response. Interim analysis of eight patients demonstrated significant induction of IFN-γ-producing-CD8(+), -CD4(+), -NK cell, and IFN-γ-producing-tumor-infiltrating-lymphocytes, signifying significant Th1 response and NK cell activation. After a median follow-up of 3.6 years, complete response (CR) + partial response (PR) = 100%, overall survival = 100%, one patient died of unrelated illness while in remission, six of seven evaluable patients are either in continuing PR/CR (5 patients) or have progression-free survival (PFS, 1 patient) exceeding the upper limit of the 95% confidence level of the genotype-specific-PFS of the phase III imatinib-monotherapy (CALGB150105/SWOGS0033), demonstrating highly promising clinical outcomes. The current trial is closed in preparation for a larger future trial. We conclude that combination of targeted therapy and immunotherapy is safe and induced significant Th1 response and NK cell activation and demonstrated highly promising clinical efficacy in GIST, thus warranting development in other tumor types.     

Class 2 Integrons Dissemination Among Multidrug Resistance (MDR) Clones of <Emphasis Type="Italic">Acinetobacter baumannii</Emphasis>

Acinetobacter baumannii has emerged as a serious problem in the hospital environment at a global scale. Previous results from our laboratory showed a high frequency of class 2 integrons in A. baumannii strains from Argentina regarding the low rate of this element in A. baumannii isolates from the rest of the world. To reveal the current epidemiology of class 2 integrons, a molecular surveillance analyzing 78 multidrug resistant (MDR) A. baumannii isolates from Argentina and Uruguay was performed, exposing the presence of class 2 integron in the 36.61% of the isolates. Class 2 integron characterization showed that the typical Tn7::In2-7 array was present in 26 out of 27 intI2 positive isolates. All intI2 positive isolates contained at least one of the Tn7 transposition genes. In addition, we identified that 18 intI2 positive isolates possessed the Tn7::In2-7 within the attTn7 site. The molecular typing evidenced that clones I and IV that do not belong to widespread European clones I and II were found among the intI2 positive isolates. Our results exposed the widely dissemination of class 2 integron among MDR A. baumannii isolates from Argentina and Uruguay, also showing the persistence of two novel clones in our region, which could explain in part the high frequency of class 2 integron found in our region.     

Neuropsychopharmacology and Neurogenetic Aspects of Executive Functioning: Should Reward Gene Polymorphisms Constitute a Diagnostic Tool to Identify Individuals at Risk for Impaired Judgment?

Executive functions are processes that act in harmony to control behaviors necessary for maintaining focus and achieving outcomes. Executive dysfunction in neuropsychiatric disorders is attributed to structural or functional pathology of brain networks involving prefrontal cortex (PFC) and its connections with other brain regions. The PFC receives innervations from different neurons associated with a number of neurotransmitters, especially dopamine (DA). Here we review findings on the contribution of PFC DA to higher-order cognitive and emotional behaviors. We suggest that examination of multifactorial interactions of an individual's genetic history, along with environmental risk factors, can assist in the characterization of executive functioning for that individual. Based upon the results of genetic studies, we also propose genetic mapping as a probable diagnostic tool serving as a therapeutic adjunct for augmenting executive functioning capabilities. We conclude that preservation of the neurological underpinnings of executive functions requires the integrity of complex neural systems including the influence of specific genes and associated polymorphisms to provide adequate neurotransmission.     

Involvement of the N-terminal B-box Domain of Arabidopsis BBX32 Protein in Interaction with Soybean BBX62 Protein

Previous studies have demonstrated that Arabidopsis thaliana BBX32 (AtBBX32) represses light signaling in A. thaliana and that expression of AtBBX32 in soybean increases grain yield in multiple locations and multiyear field trials. The BBX32 protein is a member of the B-box zinc finger family from A. thaliana and contains a single conserved Zn(2+)-binding B-box domain at the N terminus. Although the B-box domain is predicted to be involved in protein-protein interactions, the mechanism of interaction is poorly understood. Here, we provide in vitro and in vivo evidence demonstrating the physical and functional interactions of AtBBX32 with another B-box protein, soybean BBX62 (GmBBX62). Deletion analysis and characterization of the purified B-box domain indicate that the N-terminal B-box region of AtBBX32 interacts with GmBBX62. Computational modeling and site-directed mutagenesis of the AtBBX32 B-box region identified specific residues as critical for mediating the interaction between AtBBX32 and GmBBX62. This study defines the plant B-box as a protein interaction domain and offers novel insight into its role in mediating specific protein-protein interactions between different plant B-box proteins.     

Listeria monocytogenes Triggers the Cell Surface Expression of Gp96 Protein and Interacts with Its N Terminus to Support Cellular Infection

Listeria monocytogenes is an intracellular food-borne pathogen causing listeriosis in humans. This bacterium deploys an arsenal of virulence factors that act in concert to promote cellular infection. Bacterial surface proteins are of primary importance in the process of host cell invasion. They interact with host cellular receptors, inducing/modulating specific cellular responses. We previously identified Vip, a Listeria surface protein covalently attached to the bacterial cell wall acting as a key virulence factor. We have shown that Vip interacts with Gp96 localized at the surface of host cells during invasion and that this interaction is critical for a successful infection in vivo. To better understand the importance of Vip-Gp96 interaction during infection, we aimed to characterize this interaction at the molecular level. Here we demonstrate that, during infection, L. monocytogenes triggers the cellular redistribution of Gp96, inducing its exposure at the cell surface. Upon infection, Gp96 N-terminal domain is exposed to the extracellular milieu in L2071 fibroblasts and interacts with Vip expressed by Listeria. We identified Gp96 (Asp¹–Leu¹⁷⁰) as sufficient to interact with Vip; however, we also showed that the region Tyr¹⁷⁹–Leu³⁹⁰ of Gp96 is important for the interaction. Our findings unravel the Listeria-induced surface expression of Gp96 and the topology of its insertion on the plasma membrane and improve our knowledge on the Vip-Gp96 interaction during Listeria infection.     

Simvastatin decreases invasiveness of human endometrial stromal cells

Recently we reported that statins, the competitive inhibitors of the key enzyme regulating the mevalonate pathway, 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), decrease proliferation of human endometrial stromal (HES) cells. Furthermore, we found that simvastatin treatment reduces the number and the size of endometrial implants in a nude mouse model of endometriosis. The present study was undertaken to investigate the effect of simvastatin on HES cell invasiveness and on expression of selected genes relevant to invasiveness: matrix metalloproteinase 2 (MMP2), MMP3, tissue inhibitor of matrix metalloproteinase 2 (TIMP2), and CD44. Because statin-induced inhibition of HMGCR reduces the production of substrates for isoprenylation-geranylgeranyl pyrophosphate (GGPP) and farnesyl pyrophosphate (FPP)-the effects of GGPP and FPP were also evaluated. Simvastatin induced a concentration-dependent reduction of invasiveness of HES cells. This effect of simvastatin was abrogated by GGPP but not by FPP. Simvastatin also reduced the mRNA levels of MMP2, MMP3, and CD44, but increased TIMP2 mRNA; all these effects of simvastatin were partly or entirely reversed in the presence of GGPP. The present findings provide a novel mechanism of action of simvastatin on endometrial stroma that may explain reduction of endometriosis in animal models of this disease. Furthermore, the presently described effects of simvastatin are likely mediated, at least in part, by inhibition of geranylgeranylation.