Activation of cAMP-guanine exchange factor confers PKA-independent protection from hepatocyte apoptosis

cAMP has previously been shown to promote cell survival in a variety of cell types, but the downstream signaling pathway(s) of this antiapoptotic effect is unclear. Thus the role of cAMP signaling through PKA and cAMP-regulated guanine nucleotide exchange factors (cAMP-GEFs) in cAMP's antiapoptotic action was investigated in the present study. cAMP's protective effect against bile acid-, Fas ligand-, and TNF-alpha-induced apoptosis in rat hepatocytes was largely unaffected by the selective PKA inhibitor, Rp-8-(4-chlorophenylthio)-cAMP (Rp-cAMP). In contrast, a novel cAMP analog, 8-(4-chlorophenylthio)-2'-O-methyl (CPT-2-Me)-cAMP, which activated cAMP-GEFs in hepatocytes without activating PKA, protected hepatocytes against apoptosis induced by bile acids, Fas ligand, and TNF-alpha. The role of cAMP-GEF and PKA on activation of Akt, a kinase implicated in cAMP survival signaling, was investigated. Inhibition of PKA with RP-cAMP had no effect on cAMP-mediated Akt phosphorylation, whereas CPT-2-Me-cAMP, which did not activate PKA, induced phosphatidylinositol 3-kinase (PI3-kinase)-dependent activation of Akt. Pretreatment of hepatocytes with the PI3-kinase inhibitor, Ly-294002, prevented CPT-2-Me-cAMP's protective effect against bile acid and Fas ligand, but not TNF-alpha-mediated apoptosis. Glucagon, CPT-cAMP, and CPT-2-Me-cAMP all activated Rap 1, a downstream effector of cAMP-GEF. These results suggest that a PKA-independent cAMP/cAMP-GEF/Rap pathway exists in hepatocytes and that activation of cAMP-GEFs promotes Akt phosphorylation and hepatocyte survival. Thus a cAMP/cAMP-GEF/Rap/PI3-kinase/Akt signaling pathway may confer protection against bile acid- and Fas-induced apoptosis in hepatocytes.     

Identification of a truncated form of methionine sulfoxide reductase a expressed in mouse embryonic stem cells

Background  

Methionine Sulfoxide Reductase A (MsrA), an enzyme in the Msr gene family, is important in the cellular anti-oxidative stress defense mechanism. It acts by reducing the oxidized methionine sulfoxide in proteins back to sulfide and by reducing the cellular level of reactive oxygen species. MsrA, the only enzyme in the Msr gene family that can reduce the S-form epimers of methionine sulfoxide, has been located in different cellular compartments including mitochondria, cytosol and nuclei of various cell lines.     

Brief history of the Society for Melanoma Research: A community of clinicians,researchers, and friends

To commemorate the 20th Anniversary of the Society of Melanoma Research and the first International Melanoma Research Congress held in June of 2003, we have described in brief, how the Society for Melanoma Research (SMR) began, the purpose, goals, and governance of the SMR, and how the society has evolved to support new melanoma researchers. In celebration of the immense progress in treating melanoma patients over the last 20 years and the impact of the SMR on these advances, we have highlighted memories and insight from early SMR members and founders.     

Local Mechanical Stimuli Regulate Bone Formation and Resorption in Mice at the Tissue Level

Bone is able to react to changing mechanical demands by adapting its internal microstructure through bone forming and resorbing cells. This process is called bone modeling and remodeling. It is evident that changes in mechanical demands at the organ level must be interpreted at the tissue level where bone (re)modeling takes place. Although assumed for a long time, the relationship between the locations of bone formation and resorption and the local mechanical environment is still under debate. The lack of suitable imaging modalities for measuring bone formation and resorption in vivo has made it difficult to assess the mechanoregulation of bone three-dimensionally by experiment. Using in vivo micro-computed tomography and high resolution finite element analysis in living mice, we show that bone formation most likely occurs at sites of high local mechanical strain (p<0.0001) and resorption at sites of low local mechanical strain (p<0.0001). Furthermore, the probability of bone resorption decreases exponentially with increasing mechanical stimulus (R² = 0.99) whereas the probability of bone formation follows an exponential growth function to a maximum value (R² = 0.99). Moreover, resorption is more strictly controlled than formation in loaded animals, and ovariectomy increases the amount of non-targeted resorption. Our experimental assessment of mechanoregulation at the tissue level does not show any evidence of a lazy zone and suggests that around 80% of all (re)modeling can be linked to the mechanical micro-environment. These findings disclose how mechanical stimuli at the tissue level contribute to the regulation of bone adaptation at the organ level.     

The Effect on Rat Embryonic Heart Rate of Na+, K+, and Ca2+ Channel Blockers,and the Human Teratogen Phenytoin,Changes with Gestational Age

In this study, we compared the effects of four ion channel blockers on rat embryonic heart function during the organogenic period from gestational day (GD) 10 to 15, to determine the changes in dependence on ion channels during rat cardiac development. Rat embryos in culture were exposed to either the human ether‐á‐go‐go‐related gene potassium channel blocker, dofetilide (400 nM); the sodium channel blocker, lidocaine (250 μM); the L‐type calcium channel blocker, nifedipine (1.8 μM); or the multichannel blocker, phenytoin (200 μM). Lidocaine slowed the heart rate (HR) with the effect becoming more severe with increasing GD. Dofetilide slowed the embryonic HR and caused arrhythmias with the most severe effect on GD 11 to 13. Nifedipine primarily caused a negative inotropic effect except on GD 10 when it stopped the heart in most embryos. Phenytoin stopped the heart of most GD 10 to 12 embryos while on GD 13 to 15 phenytoin slowed the heart. The results demonstrate that as the rat heart develops during the organogenic period its functional dependence on ion channels changes markedly. These changes are important for understanding drug effects on the embryo during pregnancy and the methodology used provides a simple procedure for assessing drug effects on the developing heart.     

Alteration of the Thymic T Cell Repertoire by Rotavirus Infection Is Associated with Delayed Type 1 Diabetes Development in Non-Obese Diabetic Mice

Rotaviruses are implicated as a viral trigger for the acceleration of type 1 diabetes in children. Infection of adult non-obese diabetic (NOD) mice with rotavirus strain RRV accelerates diabetes development, whereas RRV infection in infant NOD mice delays diabetes onset. In this study of infant mice, RRV titers and lymphocyte populations in the intestine, mesenteric lymph nodes (MLN) and thymus of NOD mice were compared with those in diabetes-resistant BALB/c and C57BL/6 mice. Enhanced intestinal RRV infection occurred in NOD mice compared with the other mouse strains. This was associated with increases in the frequency of CD8αβ TCRαβ intraepithelial lymphocytes, and their PD-L1 expression. Virus spread to the MLN and T cell numbers there also were greatest in NOD mice. Thymic RRV infection is shown here in all mouse strains, often in combination with alterations in T cell ontogeny. Infection lowered thymocyte numbers in infant NOD and C57BL/6 mice, whereas thymocyte production was unaltered overall in infant BALB/c mice. In the NOD mouse thymus, effector CD4⁺ T cell numbers were reduced by infection, whereas regulatory T cell numbers were maintained. It is proposed that maintenance of thymic regulatory T cell numbers may contribute to the increased suppression of inflammatory T cells in response to a strong stimulus observed in pancreatic lymph nodes of adult mice infected as infants. These findings show that rotavirus replication is enhanced in diabetes-prone mice, and provide evidence that thymic T cell alterations may contribute to the delayed diabetes onset following RRV infection.     

Comparison of the replication of influenza A viruses in Chinese ring-necked pheasants and chukar partridges

We investigated the replication and transmission of avian influenza A viruses in two species thought to be intermediate hosts in the spread of influenza A viruses in live poultry markets: Chinese ring-necked pheasants and chukar partridges. All 15 hemagglutinin subtypes replicated in pheasants, and most subtypes transmitted to na?ve contact pheasants, primarily via the fecal-oral route. Many viruses were shed from the gastrointestinal tract of experimentally inoculated pheasants for 14 days or longer. Virus was isolated from the cloacal swabs of one contact pheasant for an unprecedented 45 days. Chukar partridges were less susceptible to infection with avian influenza viruses. The viruses that replicated in chukar partridges were isolated for 7 days after experimental inoculation, predominantly from the respiratory tract. We detected high neutralizing antibody titers with correspondingly low levels of serum hemagglutination inhibition antibody titers in pheasants and chukar partridges when chicken red blood cells were used in serological analyses. When horse erythrocytes were used, antibody titers were comparable to those obtained by using the neutralization assay. More importantly, the results suggested that pheasants can serve as a reservoir of influenza virus. Because of their continuous asymptomatic infection and longer stay in the markets, pheasants are ideal "carriers" of influenza A viruses. Their continued presence in live markets contributes to the perpetuation and genetic interaction of influenza viruses there. On the basis of our findings, it does not make good sense to ban quail but not pheasants from the live markets.     

Avian Egg Odour Encodes Information on Embryo Sex,Fertility and Development

Avian chemical communication is a rapidly emerging field, but has been hampered by a critical lack of information on volatile chemicals that communicate ecologically relevant information (semiochemicals). A possible, but as yet unexplored, function of olfaction and chemical communication in birds is in parent-embryo and embryo-embryo communication. Communication between parents and developing embryos may act to mediate parental behaviour, while communication between embryos can control the synchronicity of hatching. Embryonic vocalisations and vibrations have been implicated as a means of communication during the later stages of development but in the early stages, before embryos are capable of independent movement and vocalisation, this is not possible. Here we show that volatiles emitted from developing eggs of Japanese quail (Coturnix japonica) convey information on egg fertility, along with the sex and developmental status of the embryo. Specifically, egg volatiles changed over the course of incubation, differed between fertile and infertile eggs, and were predictive of embryo sex as early as day 1 of incubation. Egg odours therefore have the potential to facilitate parent-embryo and embryo-embryo interactions by allowing the assessment of key measures of embryonic development long before this is possible through other modalities. It also opens up the intriguing possibility that parents may be able to glean further relevant information from egg volatiles, such as the health, viability and heritage of embryos. By determining information conveyed by egg-derived volatiles, we hope to stimulate further investigation into the ecological role of egg odours.