Apoptosis-inducing factor regulates skeletal muscle progenitor cell number and muscle phenotype

Apoptosis Inducing Factor (AIF) is a highly conserved, ubiquitous flavoprotein localized in the mitochondrial intermembrane space. In vivo, AIF provides protection against neuronal and cardiomyocyte apoptosis induced by oxidative stress. Conversely in vitro, AIF has been demonstrated to have a pro-apoptotic role upon induction of the mitochondrial death pathway, once AIF translocates to the nucleus where it facilitates chromatin condensation and large scale DNA fragmentation. Given that the aif hypomorphic harlequin (Hq) mutant mouse model displays severe sarcopenia, we examined skeletal muscle from the aif hypomorphic mice in more detail. Adult AIF-deficient skeletal myofibers display oxidative stress and a severe form of atrophy, associated with a loss of myonuclei and a fast to slow fiber type switch, both in "slow" muscles such as soleus, as well as in "fast" muscles such as extensor digitorum longus, most likely resulting from an increase of MEF2 activity. This fiber type switch was conserved in regenerated soleus and EDL muscles of Hq mice subjected to cardiotoxin injection. In addition, muscle regeneration in soleus and EDL muscles of Hq mice was severely delayed. Freshly cultured myofibers, soleus and EDL muscle sections from Hq mice displayed a decreased satellite cell pool, which could be rescued by pretreating aif hypomorphic mice with the manganese-salen free radical scavenger EUK-8. Satellite cell activation seems to be abnormally long in Hq primary culture compared to controls. However, AIF deficiency did not affect myoblast cell proliferation and differentiation. Thus, AIF protects skeletal muscles against oxidative stress-induced damage probably by protecting satellite cells against oxidative stress and maintaining skeletal muscle stem cell number and activation.     

Serum-nutrient starvation induces cell death mediated by Bax and Puma that is counteracted by p21 and unmasked by Bcl-x(L) inhibition

The cyclin-dependent kinase inhibitor p21 (p21WAF1/Cip1) is a multifunctional protein known to promote cell cycle arrest and survival in response to p53-dependent and p53 independent stimuli. We herein investigated whether and how it might contribute to the survival of cancer cells that are in low-nutrient conditions during tumour growth, by culturing isogenic human colorectal cancer cell lines (HCT116) and breast cancer cell lines in a medium deprived in amino acids and serum. We show that such starvation enhances, independently from p53, the expression of p21 and that of the pro-apoptotic BH3-only protein Puma. Under these conditions, p21 prevents Puma and its downstream effector Bax from triggering the mitochondrial apoptotic pathway. This anti-apoptotic effect is exerted from the cytosol but it is unrelated to the ability of p21 to interfere with the effector caspase 3. The survival function of p21 is, however, overcome by RNA interference mediated Bcl-x(L) depletion, or by the pharmacological inhibitor ABT-737. Thus, an insufficient supply in nutrients may not have an overt effect on cancer cell viability due to p21 induction, but it primes these cells to die, and sensitizes them to the deleterious effects of Bcl-x(L) inhibitors regardless of their p53 status.     

Nisin-activated hydrophobic and hydrophilic surfaces: assessment of peptide adsorption and antibacterial activity against some food pathogens

An effective antimicrobial packaging or food contact surface should be able to kill or inhibit micro-organisms that cause food-borne illnesses. Setting up such systems, by nisin adsorption on hydrophilic and hydrophobic surfaces, is still a matter of debate. For this purpose, nisin was adsorbed on two types of low-density polyethylene: the hydrophobic native film and the hydrophilic acrylic acid-treated surface. The antibacterial activity was compared for those two films and it was highly dependent on the nature of the surface and the nisin-adsorbed amount. The hydrophilic surfaces presented higher antibacterial activity and higher amount of nisin than the hydrophobic surfaces. The effectiveness of the activated surfaces was assessed against Listeria innocua and the food pathogens Listeria monocytogenes, Bacillus cereus, and Staphylococcus aureus. S. aureus was more sensitive than the three other test bacteria toward both nisin-functionalized films. Simulation tests to mimic refrigerated temperature showed that the films were effective at 20 and 4 °C with no significant difference between the two temperatures after 30 min of exposure to culture media.     

Does Cognitive Function Increase over Time in the Healthy Elderly?

Background

In dementia screening, most studies have focused on early cognitive impairment by comparing patients suffering from mild dementia or mild cognitive impairment with normal subjects. Few studies have focused on modifications over time of the cognitive function in the healthy elderly. The objective of the present study was to analyze the cognitive function changes of two different samples, born > 15 years apart.

Method

A first sample of 204 cognitively normal participants was recruited in the memory clinic of Broca hospital between 1991 and 1997. A second sample of 177 cognitively normal participants was recruited in 2008–2009 in the same institution. Both samples were from the same districts of Paris and were assessed with the same neuropsychological test battery. Mean cognitive test scores were compared between 1991 and 2008 samples, between < 80 years old and ≥ 80 years old in 1991 and 2008 samples, and finally between subjects < 80 year old of 1991 sample and subjects ≥ 80 years old of the 2008 sample. Means were compared with T-tests stratified on gender, age-groups and educational level.

Results

Cognitive scores were significantly higher in the 2008 sample. Participants < 80 years old outperformed those ≥ 80 in both samples. However, participants < 80 years old in 1991 sample and subjects ≥ 80 in the 2008 sample, born on average in 1923, performed mostly identically.

Conclusion

This study showed a significant increase of cognitive scores over time. Further, contemporary octogenarians in the later sample performed like septuagenarians in the former sample. These findings might be consistent with the increase in life expectancy and life span in good health. The study highlights the necessity to take into account factors which may contaminate and artificially inflate the age-related differences in favor of younger to the older adults.     

Identification of PDZ ligands by docking-based virtual screening for the development of novel analgesic agents

Disrupting the interaction between the PDZ protein, PSD-95, and its target ligands (such as the glutamate NMDA receptor or the serotonin 5-HT_2A receptor) was found to reduce hyperalgesia in various models of neuropathic pain. Here, we set out to identify lead molecules which would interact with PSD-95, and hence, would potentially display analgesic activity. We describe the virtual screening of the Asinex and Cambridge databases which together contain almost one million molecules. Using three successive docking filters and visual inspection, we identified three structural classes of molecules and synthesized a potential lead compound from each class. The binding of the molecules with the PDZ domains of PSD-95 was assessed by ¹H–¹⁵N HSQC NMR experiments. The analgesic activity of the best ligand, quinoline 2, was evaluated in vivo in a model of neuropathic pain and showed promising results.     

Death among geladas (Theropithecus gelada): a broader perspective on mummified infants and primate thanatology

Despite intensive study in humans, responses to dying and death have been a neglected area of research in other social mammals, including nonhuman primates. Two recent reports [Anderson JR, Gillies A, Lock LC. 2010. Pan thanatology. Current Biology 20:R349–R351; Biro D, Humle T, Koops K, Souse C, Hayashi M, Matsuzawa T. 2010. Chimpanzee mothers at Bossou, Guinea carry the mummified remains of their dead infants. Current Biology 20:R351–R352] offered exciting new insights into behavior toward dying and dead conspecifics in our closest living relatives—chimpanzees. Here, we provide a comparative perspective on primate thanatology using observations from a more distant human relative—gelada monkeys (Theropithecus gelada)—and discuss how gelada reactions to dead and dying groupmates differ from those recently reported for chimpanzees. Over a 3.75‐year study period, we observed 14 female geladas at Guassa, Ethiopia carrying dead infants from 1 hr to ≥48 days after death. Dead infants were carried by their mothers, other females in their group, and even by females belonging to other groups. Like other primate populations in which extended (>10 days) infant carrying after death has been reported, geladas at Guassa experience an extreme climate for primates, creating conditions which may favor slower rates of decomposition of dead individuals. We also witnessed the events leading up to the deaths of two individuals and the responses by groupmates to these dying individuals. Our results suggest that while chimpanzee mothers are not unique among primates in carrying their dead infants for long periods, seemingly “compassionate” caretaking behavior toward dying groupmates may be unique to chimpanzees among nonhuman primates (though it remains unknown whether such “compassionate” behavior occurs outside captivity). Am. J. Primatol. 73:405–409, 2011. © 2010 Wiley‐Liss, Inc.     

The phosphoinositide phosphatase MTM-1 regulates apoptotic cell corpse clearance through CED-5-CED-12 in C. elegans

Multicellular organisms use programmed cell death to eliminate unwanted or potentially harmful cells. Improper cell corpse removal can lead to autoimmune diseases. The development of interventional therapies that increase engulfment activity could represent an attractive approach to treat such diseases. Here, we describe mtm-1, the Caenorhabditis elegans homolog of human myotubularin 1, as a potential negative regulator of apoptotic cell corpse clearance. Loss of mtm-1 function leads to substantially reduced numbers of persistent cell corpses in engulfment mutants, which is a result of a restoration of engulfment function rather than of impaired or delayed programmed cell death. Epistatic analyses place mtm-1 upstream of the ternary GEF complex, which consists of ced-2, ced-5 and ced-12, and parallel to mig-2. Over-activation of engulfment results in the removal of viable cells that have been brought to the verge of death under limiting caspase activity. In addition, mtm-1 also promotes phagosome maturation in the hermaphrodite gonad, potentially through CED-1 receptor recycling. Finally, we show that the CED-12 PH domain can bind to PtdIns(3,5)P(2) (one target of MTM-1 phosphatase activity), suggesting that MTM-1 might regulate CED-12 recruitment to the plasma membrane.     

Attenuated Bordetella pertussis vaccine candidate BPZE1 promotes human dendritic cell CCL21-induced migration and drives a Th1/Th17 response

New vaccines against pertussis are needed to evoke full protection and long-lasting immunological memory starting from the first administration in neonates--the major target of the life-threatening pertussis infection. A novel live attenuated Bordetella pertussis vaccine strain, BPZE1, has been developed by eliminating or detoxifying three important B. pertussis virulence factors: pertussis toxin, dermonecrotic toxin, and tracheal cytotoxin. We used a human preclinical ex vivo model based on monocyte-derived dendritic cells (MDDCs) to evaluate BPZE1 immunogenicity. We studied the effects of BPZE1 on MDDC functions, focusing on the impact of Bordetella-primed dendritic cells in the regulation of Th and suppressor T cells (Ts). BPZE1 is able to activate human MDDCs and to promote the production of a broad spectrum of proinflammatory and regulatory cytokines. Moreover, conversely to its parental wild-type counterpart BPSM, BPZE1-primed MDDCs very efficiently migrate in vitro in response to the lymphatic chemokine CCL21, due to the inactivation of pertussis toxin enzymatic activity. BPZE1-primed MDDCs drove a mixed Th1/Th17 polarization and also induced functional Ts. Experiments performed in a Transwell system showed that cell contact rather than the production of soluble factors was required for suppression activity. Overall, our findings support the potential of BPZE1 as a novel live attenuated pertussis vaccine, as BPZE1-challenged dendritic cells might migrate from the site of infection to the lymph nodes, prime Th cells, mount an adaptive immune response, and orchestrate Th1/Th17 and Ts responses.