No abstract

Natural killer (NK) cells have been reported to control adaptive immune responses that occur in lymphoid organs at the early stages of immune challenge. The physiological purpose of such regulatory activity remains unclear, because it generally does not confer a survival advantage. We found that NK cells specifically eliminated activated CD4(+) T cells in the salivary gland during chronic murine cytomegalovirus (MCMV) infection. This was dependent on TNF-related apoptosis inducing ligand (TRAIL) expression by NK cells. Although NK cell-mediated deletion of CD4(+) T cells prolonged the chronicity of infection, it also constrained viral-induced autoimmunity. In the absence of this activity, chronic infection was associated with a Sjogren's-like syndrome characterized by focal lymphocytic infiltration into the glands, production of autoantibodies, and reduced saliva and tear secretion. Thus, NK cells are an important homeostatic control that balances the efficacy of adaptive immune responses with the risk of developing autoimmunity.

Integrative Physiology B lood vessels consist of 2 major cell types, endothelial and mural cells, such as pericytes and vascular smooth muscle cells (VSMC), which surround the endothelium. Regulator of G-protein signaling 5 (RGS5) is expressed in mural cells and has emerged as a crucial modulator of vascular pathology in cancer. For instance, we have demonstrated that RGS5 is highly upregulated in angiogenic tumor pericytes.1 Loss of RGS5 results in pericyte maturation and normalization of tumor vasculature.2,3 Moreover, we showed a crucial role for RGS5 in regulating vascular barrier function in tumors and in brain capillaries during ischemia, and also provided the first genetic evidence that RGS5 is involved in vascular wall remodeling in adults. 2A striking feature of RGS5 expression is its dynamic nature in various physiological and pathological states, which indicates a role in adaptive processes. 1,[4][5][6] This is consistent with RGS5 being a member of the extended family of RGS molecules, which are modulators of G-protein-coupled receptors (GPCRs). G-protein signaling pathways rely on rapid on-off kinetics, and RGS molecules act as GTPaseactivating proteins (GAP) for heterotrimeric G proteins and, as such, regulate duration and intensity of signaling events. They contain a highly conserved carboxyl-terminal RGS domain that confers the catalytic function for active Gα subunits. Members of the R4/B subfamily, which include, among others, RGS 2, 4, and 5, are the smallest RGS Original received September 21, 2012; revision received January 7, 2013; accepted January 9, 2013. In December 2012, the average time from submission to first decision for all original research papers submitted to Circulation Research was 14.5 days.

The evolutionary survival of viruses relies on their ability to disseminate infectious progeny to sites of transmission. The capacity to subvert apoptosis is thought to be crucial for ensuring efficient viral replication in permissive cells, but its role in viral dissemination in vivo has not been considered. We show here that the murine cytomegalovirus (MCMV) m38.5 protein specifically counters the action of Bax. As predicted from our biochemical data, the capacity of m38.5 to inhibit apoptosis is only apparent in cells unable to activate Bak. Deletion of m38.5 resulted in an attenuated growth of MCMV in vitro. In vivo replication of the Deltam38.5 virus was not significantly impaired in visceral organs. However, m38.5 played a central role in protecting leukocytes from Bax-mediated apoptosis, thereby promoting viral dissemination to the salivary glands, the principal site of transmission. These results establish that in vivo MCMV replication induces the activation of Bax in leukocytes, but not other permissive cells, and that MCMV interferes with this process to attain maximum dissemination.

A double-blind randomized controlled trial with a paired split-scar design compared verapamil, an L-type Ca2+ channel antagonist, and triamcinolone for prevention of keloid recurrence after excision. Ca2+ channel blocking activity of verapamil in keloid cells was explored. One keloid was excised per subject and each wound half randomized to receive intralesional injections of triamcinolone (10 mg/ml) or verapamil (2.5 mg/ml) at monthly intervals (4 doses). Interim analysis was performed after 14 subjects were completed. Survival analysis demonstrated significantly higher keloid recurrence with verapamil compared to triamcinolone 12 months post-surgery (log-rank test, p = 0.01) and higher overall risk of recurrence with verapamil (hazard ratio 8.44, 95% CI 1.62-44.05). The study was terminated early according to the stopping guideline (p < 0.05). Verapamil is safe but not as effective as triamcinolone in preventing keloid recurrence after excision. Further study is necessary to determine if clinical response to verapamil is linked to modulation of intracellular Ca2+.

No abstract

SummaryThe NK gene complex (NKC) on mouse chromosome 6 encodes receptors that are expressed on NK cells, such as Ly49H, and is involved in regulating NK cell control of virus infections, such as murine cytomegalovirus (MCMV). In the present study, we investigated the level of allelic heterogeneity in NKC loci in populations of outbred wild mice. This work revealed extensive levels of heterogeneity within two wild mouse populations. Analysis of MCMV replication in a population of specific pathogen-free outbred wild mice revealed that low viral titres, which are normally associated with the Cmv1 r allele of the Cmv1 host resistance locus, were not prevalent in the mice tested. Hence, NKC-mediated resistance associated with Cmv1 r /Ly49H-like effects was rare in this population. Overall, these data indicate that the NKC region is highly polymorphic and thus it is very likely that it confers on mice sufficient variability to cope with infection by a range of pathogens.

Infection with murine cytomegalovirus (MCMV) has contributed to understanding many aspects of human infection and, additionally, has provided important insight to understanding complex cellular responses. Dendritic cells (DCs) are a major target for MCMV infection. Here, we analyze the effects of MCMV infection on DC viability, and show that infected DCs become resistant to apoptosis induced by growth factor deprivation. The precise contribution of changes in the expression of Bcl-2 family proteins has been assessed and a new checkpoint in the apoptotic pathway identified. Despite their resistance to apoptosis, MCMV-infected DCs showed Bax to be tightly associated with mitochondria and, together with Bak, forming high molecular weight oligomers, changes normally associated with apoptotic cell death. Exposure of a constitutively occluded Bax NH2-terminal epitope was blocked after infection. These results suggest that MCMV has evolved a novel strategy for inhibiting apoptosis and provide evidence that apoptosis can be regulated after translocation, integration, and oligomerization of Bax at the mitochondrial membrane.