Signal transduction with the diatomic radical nitric oxide (NO) is involved in a number of important physiological processes, including smooth muscle relaxation and neurotransmission. Soluble guanylate cyclase (sGC), a heterodimeric enzyme that converts guanosine triphosphate to cyclic guanosine monophosphate, is a critical component of this signaling pathway. sGC is a hemoprotein; it is through the specific interaction of NO with the sGC heme that sGC is activated. Over the last decade, much has been learned about the unique heme environment of sGC and its interaction with ligands like NO and carbon monoxide. This review will focus on the role of sGC in signaling, its relationship to the other nucleotide cyclases, and on what is known about sGC genetics, heme environment and catalysis. The latest understanding in regard to sGC will be incorporated to build a model of sGC structure, activation, catalytic mechanism and deactivation.

Exposure to psychosocial stress is a risk factor for many diseases, including atherosclerosis1,2. While incompletely understood, interaction between the psyche and the immune system provides one potential mechanism linking stress and disease inception and progression. Known crosstalk between the brain and immune system includes the hypothalamic–pituitary–adrenal axis, which centrally drives glucocorticoid production in the adrenal cortex, and the sympathetic–adrenal–medullary axis, which controls stress–induced catecholamine release in support of the fight–or–flight reflex3,4. It remains unknown however if chronic stress changes hematopoietic stem cell activity. Here we show that stress increases proliferation of these most primitive progenitors, giving rise to higher levels of disease–promoting inflammatory leukocytes. We found that chronic stress induced monocytosis and neutrophilia in humans. While investigating the source of leukocytosis in mice, we discovered that stress activates upstream hematopoietic stem cells. Sympathetic nerve fibers release surplus noradrenaline, which uses the β3 adrenergic receptor to signal bone marrow niche cells to decrease CXCL12 levels. Consequently, elevated hematopoietic stem cell proliferation increases output of neutrophils and inflammatory monocytes. When atherosclerosis–prone ApoE−/− mice encounter chronic stress, accelerated hematopoiesis promotes plaque features associated with vulnerable lesions that cause myocardial infarction and stroke in humans.

Background Burnout is characterized by physical and emotional exhaustion from long-term exposure to emotionally demanding work. Burnout affects interpersonal skills, job performance, career satisfaction, and psychological health. However, little is known about the burden of burnout among healthcare providers in sub-Saharan Africa. Methods Relevant articles were identified through a systematic review of PubMed, Web of Science (Thomson Reuters), and PsycINFO (EBSCO). Studies were selected for inclusion if they examined a quantitative measure of burnout among healthcare providers in sub-Saharan Africa. Results A total of 65 articles met our inclusion criteria for this systematic review. Previous studies have examined burnout in sub-Saharan Africa among physicians (N = 12 articles), nurses (N = 26), combined populations of healthcare providers (N = 18), midwives (N = 2), and medical or nursing students (N = 7). The majority of studies assessed burnout using the Maslach Burnout Inventory. The highest levels of burnout were reported among nurses, although all healthcare providers showed high burnout. Burnout among healthcare providers is associated with their work environments, interpersonal and professional conflicts, emotional distress, and low social support. Conclusions Available studies on this topic are limited by several methodological challenges. More rigorously designed epidemiologic studies of burnout among healthcare providers are warranted. Health infrastructure improvements will eventually be essential, though difficult to achieve, in under-resourced settings. Programs aimed at raising awareness and coping with burnout symptoms through stress management and resilience enhancement trainings are also needed.

The relaxation response (RR) is the counterpart of the stress response. Millennia-old practices evoking the RR include meditation, yoga and repetitive prayer. Although RR elicitation is an effective therapeutic intervention that counteracts the adverse clinical effects of stress in disorders including hypertension, anxiety, insomnia and aging, the underlying molecular mechanisms that explain these clinical benefits remain undetermined. To assess rapid time-dependent (temporal) genomic changes during one session of RR practice among healthy practitioners with years of RR practice and also in novices before and after 8 weeks of RR training, we measured the transcriptome in peripheral blood prior to, immediately after, and 15 minutes after listening to an RR-eliciting or a health education CD. Both short-term and long-term practitioners evoked significant temporal gene expression changes with greater significance in the latter as compared to novices. RR practice enhanced expression of genes associated with energy metabolism, mitochondrial function, insulin secretion and telomere maintenance, and reduced expression of genes linked to inflammatory response and stress-related pathways. Interactive network analyses of RR-affected pathways identified mitochondrial ATP synthase and insulin (INS) as top upregulated critical molecules (focus hubs) and NF-κB pathway genes as top downregulated focus hubs. Our results for the first time indicate that RR elicitation, particularly after long-term practice, may evoke its downstream health benefits by improving mitochondrial energy production and utilization and thus promoting mitochondrial resiliency through upregulation of ATPase and insulin function. Mitochondrial resiliency might also be promoted by RR-induced downregulation of NF-κB-associated upstream and downstream targets that mitigates stress.

The regulon controlled by the leucine-responsive regulatory protein (Lrp) of Escherichia coli consists of over 40 genes and proteins whose expression is regulated, either positively or negatively, by Lrp. The gltBDF operon, encoding glutamate synthase, was originally identified as a member of the Lrp regulon through a twodimensional electrophoretic analysis of polypeptides from isogenic strains containing or lacking a functional Lrp protein. We have now demonstrated that Lrp regulates the transcription of gltBDF::lacZ operon fusions. Relative to expression in glucose minimal 3-(N-morpholino)propanesulfonic acid (MOPS) medium, gltBDF::lacZ expression in an lrp+ strain is repressed 2.2-fold in the presence of 10 mM exogenous leucine and 16-fold in Luria broth. Repression of gltBDF::lacZ expression by leucine or Luria broth is not seen for an isogenic strain containing a TnlO insertion in lrp, and expression of gItBDF::lacZ is 44-fold lower than in the lrp+ strain when both are grown in glucose minimal MOPS medium. Lrp binds specifically to DNA fragments containing the gltBDF promoter region. Saturating levels of leucine do not abolish binding of Lrp upstream of glBDF but merely increase its apparent dissociation constant from 2.0 to 6.9 nM. Electrophoretic analysis of the Lrp regulon established that target proteins differ greatly in the degree to which the effect of Lrp on their expression is antagonized by leucine. On the basis of our present results, we present a model for positive regulation of target genes by Lrp. Insensitivity to leucine would be expected when the effective intracellular concentration of Lrp is high relative to the affinity of Lrp binding sites required for transcription of the target gene. At lower concentrations of Lrp, transcription of the target gene should be sensitive to leucine. This model suggests that regulation of the concentration of active Lrp is critical to control of the Lrp regulon.The Lrp (leucine-responsive regulatory protein) regulon of K-12 strains of Escherichia coli consists of over 40 polypeptides whose expression is regulated, either positively or negatively, by Lrp (2,6,8,11,12,17,20,21). The first genes and operons of the Lrp regulon to be recognized were regulated in response to the presence or absence of exogenous leucine. For these leucine-sensitive genes and operons, Lrp can be a positive or a negative regulator of expression, and the effect of Lrp is antagonized in the presence of exogenous leucine. The best studied of these operons is the ilvIH operon, encoding acetohydroxy acid synthase form III (5). Lrp is a transcriptional activator of ilvIH expression (29), and the presence of leucine in the medium reduces this activation 5-to 10-fold (9). Two-dimensional gel electrophoretic analysis of net protein synthesis in strains containing or lacking a functional lrp gene and grown in the presence and absence of leucine detected a number of known and unknown proteins regulated by Lrp in a leucine-sensitive manner. That study also revealed an even larger number of p...

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Objective: The objective was to assess the feasibility and acceptability of nine positive psychology exercises delivered to patients hospitalized for suicidal thoughts or behaviors, and to secondarily explore the relative impact of the exercises. Method: Participants admitted to a psychiatric unit for suicidal ideation or behavior completed daily positive psychology exercises while hospitalized. Likert-scale ratings of efficacy (optimism, hopelessness, perceived utility) and ease of completion were consolidated and compared across exercises using mixed models accounting for age, missing data and exercise order. Overall effects of exercise on efficacy and ease were also examined using mixed models. Results: Fifty-two (85.3%) of 61 participants completed at least one exercise, and 189/213 (88.7%) assigned exercises were completed. There were overall effects of exercise on efficacy (χ 2 =19.39; P=.013) but not ease of completion (χ 2 =11.64; P=.17), accounting for age, order and skipped exercises. Effect (Cohen's d) of exercise on both optimism and hopelessness was moderate for the majority of exercises. Exercises related to gratitude and personal strengths ranked highest. Both gratitude exercises had efficacy scores that were significantly (P=.001) greater than the lowest-ranked exercise (forgiveness). Conclusion: In this exploratory project, positive psychology exercises delivered to suicidal inpatients were feasible and associated with short-term gains in clinically relevant outcomes.

The enzyme-soluble guanylate cyclase (sGC), which converts GTP to cGMP, is a receptor for the signaling agent nitric oxide (NO). YC-1, a synthetic benzylindazole derivative, has been shown to activate sGC in an NO-independent fashion. In the presence of carbon monoxide (CO), which by itself activates sGC approximately 5-fold, YC-1 activates sGC to a level comparable to stimulation by NO alone. We have used kinetic analyses and resonance Raman spectroscopy (RR) to investigate the interaction of YC-1 and CO with guanylate cyclase. In the presence of CO and 200 microM YC-1, the V(max)/K(m GTP) increases 226-fold. While YC-1 does not perturb the RR spectrum of the ferrous form of baculovirus/Sf9 cell expressed sGC, it induces a shift in the Fe-CO stretching frequency for the CO-bound form from 474 to 492 cm(-1). Similarly, YC-1 has no effect on the RR spectrum of ferrous beta1(1-385), the isolated sGC heme-binding domain, but shifts the nu(Fe-CO) of CO-beta1(1-385) from 478 to 491 cm(-1), indicating that YC-1 binds in heme-binding region of sGC. In addition, the CO-bound forms of sGC and beta1(1-385) in the presence of YC-1 lie on the nu(Fe-CO) vs nu(C-O) correlation curve for proximal ligands with imidazole character, which suggests that histidine remains the heme proximal ligand in the presence of YC-1. Interestingly, YC-1 does not shift nu(Fe-CO) for the CO-bound form of H105G(Im), the imidazole-rescued heme ligand mutant of beta1(1-385). The data are consistent with binding of CO and YC-1 to the sGC heme-binding domain leading to conformational changes that give rise to an increase in catalytic turnover and a change in the electrostatic environment of the heme pocket.