Population and public health ethics in Canada: a snapshot of current national initiatives and future issues.

To date, some work has been undertaken to define a code and stewardship framework for public health ethics. However, gaps in our understanding and application of ethics to the field of population and public health (PPH) remain. This paper presents the approach to building capacity for PPH ethics by three national-level organizations: the Canadian Institutes of Health Research-Institute of Population and Public Health, the National Collaborating Centre for Healthy Public Policy, and the Public Health Agency of Canada. By first looking at each of the organizations' respective activities and then across organizations, we synthesize our common approaches, highlight future directions and pose questions aimed at stimulating dialogue about the role of, and challenges confronting, the emerging field of PPH ethics in Canada.

HCMV pUS28 initiates pro-migratory signaling via activation of Pyk2 kinase.

BACKGROUND: Human Cytomegalovirus (HCMV) has been implicated in the acceleration of vascular disease and chronic allograft rejection. Recently, the virus has been associated with glioblastoma and other tumors. We have previously shown that the HCMV-encoded chemokine receptor pUS28 mediates smooth muscle cell (SMC) and macrophage motility and this activity has been implicated in the acceleration of vascular disease. pUS28 induced SMC migration involves the activation of the protein tyrosine kinases (PTKs) Src and Focal adhesion kinase as well as the small GTPase RhoA. The PTK Pyk2 has been shown to play a role in cellular migration and formation of cancer, especially glioblastoma. The role of Pyk2 in pUS28 signaling and migration are unknown. METHODS: In the current study, we examined the involvement of the PTK Pyk2 in pUS28-induced cellular motility. We utilized in vitro migration of SMC to determine the requirements for Pyk2 in pUS28 pro-migratory signaling. We performed biochemical analysis of Pyk2 signaling in response to pUS28 activation to determine the mechanisms involved in pUS28 migration. We performed mass spectrometric analysis of Pyk2 complexes to identify novel Pyk2 binding partners. RESULTS: Expression of a mutant form of Pyk2 lacking the autophosphorylation site (Tyr-402) blocks pUS28-mediated SMC migration in response to CCL5, while the kinase-inactive Pyk2 mutant failed to elicit the same negative effect on migration. pUS28 stimulation with CCL5 results in ligand-dependent and calcium-dependent phosphorylation of Pyk2 Tyr-402 and induced the formation of an active Pyk2 kinase complex containing several novel Pyk2 binding proteins. Expression of the autophosphorylation null mutant Pyk2 F402Y did not abrogate the formation of an active Pyk2 kinase complex, but instead prevented pUS28-mediated activation of RhoA. Additionally, pUS28 activated RhoA via Pyk2 in the U373 glioblastoma cells. Interestingly, the Pyk2 kinase complex in U373 contained several proteins known to participate in glioma tumorigenesis. CONCLUSIONS: These findings represent the first demonstration that pUS28 signals through Pyk2 and that this PTK participates in pUS28-mediated cellular motility via activation of RhoA. Furthermore, these results provide a potential mechanistic link between HCMV-pUS28 and glioblastoma cell activation.

Differential ligand binding to a human cytomegalovirus chemokine receptor determines cell type-specific motility.

While most chemokine receptors fail to cross the chemokine class boundary with respect to the ligands that they bind, the human cytomegalovirus (HCMV)-encoded chemokine receptor US28 binds multiple CC-chemokines and the CX(3)C-chemokine Fractalkine. US28 binding to CC-chemokines is both necessary and sufficient to induce vascular smooth muscle cell (SMC) migration in response to HCMV infection. However, the function of Fractalkine binding to US28 is unknown. In this report, we demonstrate that Fractalkine binding to US28 not only induces migration of macrophages but also acts to inhibit RANTES-mediated SMC migration. Similarly, RANTES inhibits Fractalkine-mediated US28 migration in macrophages. While US28 binding of both RANTES and Fractalkine activate FAK and ERK-1/2, RANTES signals through Galpha12 and Fractalkine through Galphaq. These findings represent the first example of differential chemotactic signaling via a multiple chemokine family binding receptor that results in migration of two different cell types. Additionally, the demonstration that US28-mediated chemotaxis is both ligand-specific and cell type-specific has important implications in the role of US28 in HCMV pathogenesis.

Race, science and a novel: an interdisciplinary dialogue.

In the novel Racists by Kunal Basu (2006), two competing scientists initiate an experiment that they believe will prove which race is superior. The research subjects, one white and one black infant, are sequestered on an isolated island in the care of a mute nurse. The contest must be waged in a 'natural laboratory' with no artificial interventions and with the prospect that one will die at the hands of the other. The politics of empire, the slave trade and the advent of a new scientific way of viewing life, Darwinism, set the stage for the fictional experiment, but the ramifications of such thinking extend into the present. Coming from the disciplines of nursing, philosophy and science, we discuss how a novel can illuminate the moral dimensions of science and healthcare. The critical distance afforded by the novel provides a rich terrain for the examination of issues such as race, care and the purity of science. Despite the recent dominance of social explanations of race, science requires the examination of the differences between human beings at the biological level. The view that biology is destiny is a powerful one with dangerous consequences, especially since the belief that certain human beings' destinies are far worthier than others is a corollary of such a view. In this paper, we present the cross-disciplinary conversation, which has been facilitated by this novel. We hope this will inform ethics educators of the rich potential of using fiction as a pedagogical tool.

When is it permissible to dismiss a family who refuses vaccines? Legal, ethical and public health perspectives.

Although immunization is one of the most important health interventions of the 20th century, cases of infectious disease continue to occur. There are parents who refuse immunization for their children, creating a dilemma for the primary care physician who must consider the best interest of the individual child as well as that of the community. Some physicians, when faced with parents who refuse immunization on behalf of their children, choose to dismiss these families from their practice. Given the existing shortage of primary care physicians across Canada, this decision to dismiss families based on vaccine refusal has far-reaching implications. The present article explores this issue in the Canadian context from a legal, ethical and public health perspective.

The promise of public health: ethical reflections.

Public health is in the spotlight of public and political concern, providing a unique window of opportunity for its revitalization and restoration as a pillar of the Canadian health care system. The establishment of a Federal Public Health Agency is a critical first step. The public health community has identified key challenges toward this renewal. However, public health ethics have received little attention and, when addressed, have focussed almost exclusively on communicable diseases. The ethical issues inherent in public health transcend infectious diseases and are distinct from clinical and research ethics. Identifying and addressing ethical issues at the heart of public health, including the public interest and the common good, as well as fundamental issues related to the core functions of public health will be essential if this revitalization of public health is to be achieved. While legal and regulatory reforms are necessary, they will not be sufficient to adequately address fundamental questions of the valuing of public health or the ethical issues in public health. Elements of a research agenda on the ethical foundations of public health reform are identified here.

Mouse cytomegalovirus M33 is necessary and sufficient in virus-induced vascular smooth muscle cell migration.

Mouse cytomegalovirus (MCMV) encodes two potential seven-transmembrane-spanning proteins with homologies to cellular chemokine receptors, M33 and M78. While these virus-encoded chemokine receptors are necessary for the in vivo pathogenesis of MCMV, the function of these proteins is unknown. Since vascular smooth muscle cell (SMC) migration is of critical importance for the development of atherosclerosis and other vascular diseases, the ability of M33 to promote SMC motility was assessed. Similar to human CMV, MCMV induced the migration of mouse aortic SMCs but not mouse fibroblasts. To demonstrate whether M33 was required for MCMV-induced SMC migration, we employed interfering-RNA technology to specifically knock down M33 expression in the context of viral infection. The knockdown of M33 resulted in the specific reduction of M33 protein expression and ablation of MCMV-mediated SMC migration but failed to reduce viral growth in cultured cells. Adenovirus vector expression of M33 was sufficient to promote SMC migration, which was enhanced in the presence of recombinant mouse RANTES (mRANTES). In addition, M33 promoted the activation of Rac1 and extracellular signal-related kinase 1/2 upon stimulation with mRANTES. These findings demonstrate that mRANTES is a ligand for this chemokine receptor and that the activation of M33 occurs in a ligand-dependent manner. Thus, M33 is a functional homologue of US28 that is required for MCMV-induced vascular SMC migration.

Human cytomegalovirus-encoded G protein-coupled receptor US28 mediates smooth muscle cell migration through Galpha12.

Coupling of G proteins to ligand-engaged chemokine receptors is the paramount event in G-protein-coupled receptor signal transduction. Previously, we have demonstrated that the human cytomegalovirus-encoded chemokine receptor US28 mediates human vascular smooth muscle cell (SMC) migration in response to either RANTES or monocyte chemoattractant protein 1. In this report, we identify the G proteins that couple with US28 to promote vascular SMC migration and identify other signaling molecules that play critical roles in this process. US28-mediated cellular migration was enhanced with the expression of the G-protein subunits Galpha12 and Galpha13, suggesting that US28 may functionally couple to these G proteins. In correlation with this observation, US28 was able to activate RhoA, a downstream effector of Galpha12 and Galpha13 in cell types with these G proteins but not in those without them and activation of RhoA was dependent on US28 stimulation with RANTES. In addition, inactivation of RhoA or the RhoA-associated kinase p160ROCK with a dominant-negative mutant of RhoA or the small molecule inhibitor Y27632, respectively, abrogated US28-induced SMC migration. The data presented here suggest that US28 functionally signals through Galpha12 family G proteins and RhoA in a ligand-dependent manner and these signaling molecules are important for the ability of US28 to induce cellular migration.

Human cytomegalovirus chemokine receptor US28-induced smooth muscle cell migration is mediated by focal adhesion kinase and Src.

The human cytomegalovirus-encoded chemokine receptor US28 induces arterial smooth muscle cell (SMC) migration; however, the underlying mechanisms involved in this process are unclear. We have previously shown that US28-mediated SMC migration occurs by a ligand-dependent process that is sensitive to protein-tyrosine kinase inhibitors. We demonstrate here that US28 signals through the non-receptor protein-tyrosine kinases Src and focal adhesion kinase (FAK) and that this activity is necessary for US28-mediated SMC migration. In the presence of RANTES (regulated on activation normal T cell expressed and secreted), US28 stimulates the production of a FAK.Src kinase complex. Interestingly, Src co-immunoprecipitates with US28 in a ligand-dependent manner. This association occurs earlier than the formation of the FAK.Src kinase complex, suggesting that US28 activates Src before FAK. US28 binding to RANTES also promotes the formation of a Grb2.FAK complex, which is sensitive to treatment with the Src inhibitor PP2, further highlighting the critical role of Src in US28 activation of FAK. Human cytomegalovirus US28-mediated SMC migration is inhibited by treatment with PP2 and through the expression of either of two dominant negative inhibitors of FAK (F397Y and NH2-terminal amino acids 1-401). These findings demonstrate that activation of FAK and Src plays a critical role in US28-mediated signaling and SMC migration.