Thyroid hormone (TH) is essential for vertebrate development and the homeostasis of most adult tissues, including bone. TH stimulates target gene expression through the nuclear thyroid receptors TRα and TRβ; however, TH also has rapid, transcription-independent (nongenomic) effects. We found a previously uncharacterized plasma membrane-bound receptor that was necessary and sufficient for nongenomic TH signaling in several cell types. We determined that this receptor is generated by translation initiation from an internal methionine of TRα, which produces a transcriptionally incompetent protein that is palmitoylated and associates with caveolin-containing plasma membrane domains. TH signaling through this receptor stimulated a pro-proliferative and pro-survival program by increasing the intracellular concentrations of calcium, nitric oxide (NO), and cyclic guanosine monophosphate (cGMP), which led to the sequential activation of protein kinase G II (PKGII), the tyrosine kinase Src, and extracellular signal-regulated kinase (ERK) and Akt signaling. Hypothyroid mice exhibited a cGMP-deficient state with impaired bone formation and increased apoptosis of osteocytes, which was rescued by a direct stimulator of guanylate cyclase. Our results link nongenomic TH signaling to a previously uncharacterized membrane-bound receptor, and identify NO synthase, guanylate cyclase, and PKGII as TH effectors that activate kinase cascades to regulate cell survival and proliferation.

Most FDA-approved treatments for osteoporosis target osteoclastic bone resorption. Only PTH derivatives improve bone formation, but they have drawbacks, and novel bone-anabolic agents are needed. Nitrates, which generate NO, improved BMD in estrogen-deficient rats and may improve bone formation markers and BMD in post-menopausal women. However, nitrates are limited by induction of oxidative stress and development of tolerance, and may increase cardiovascular mortality after long-term use. Here we studied nitrosyl-cobinamide (NO-Cbi), a novel, direct NO-releasing agent, in a mouse model of estrogen deficiency-induced osteoporosis. In murine primary osteoblasts, NO-Cbi increased intracellular cGMP, Wnt/β-catenin signaling, proliferation, and osteoblastic gene expression, and protected cells from apoptosis. Correspondingly, in intact and ovariectomized (OVX) female C57Bl/6 mice, NO-Cbi increased serum cGMP concentrations, bone formation, and osteoblastic gene expression, and in OVX mice, it prevented osteocyte apoptosis. NO-Cbi reduced osteoclasts in intact mice and prevented the known increase in osteoclasts in OVX mice, partially through a reduction in the RANKL/osteoprotegerin gene expression ratio, which regulates osteoclast differentiation, and partially through direct inhibition of osteoclast differentiation, observed in vitro in the presence of excess RANKL. The positive NO effects in osteoblasts were mediated by cGMP/PKG, but some of the osteoclast-inhibitory effects appeared to be cGMP-independent. NO-Cbi increased trabecular bone mass in both intact and OVX mice, consistent with its in vitro effects on osteoblasts and osteoclasts. NO-Cbi is a novel direct NO-releasing agent that, in contrast to nitrates, does not generate oxygen radicals, and combines anabolic and anti-resorptive effects in bone, making it an excellent candidate for treating osteoporosis.

Osteoporosis is a major health problem leading to fractures that cause substantial morbidity and mortality. Current osteoporosis therapies have significant drawbacks, creating a need for novel bone-anabolic agents. We previously showed that the nitric oxide/cyclic GMP (cGMP)/protein kinase G pathway mediates some of the anabolic effects of estrogens and mechanical stimulation in osteoblasts and osteocytes, leading us to hypothesize that cGMP-elevating agents may have bone-protective effects. We tested cinaciguat, a prototype of a novel class of soluble guanylate cyclase activators, in a mouse model of estrogen deficiency-induced osteoporosis. Compared with sham-operated mice, ovariectomized mice had lower serum cGMP concentrations, which were largely restored to normal by treatment with cinaciguat or low-dose 17β-estradiol. Microcomputed tomography of tibiae showed that cinaciguat significantly improved trabecular bone microarchitecture in ovariectomized animals, with effect sizes similar to those obtained with estrogen replacement therapy. Cinaciguat reversed ovariectomy-induced osteocyte apoptosis as efficiently as estradiol and enhanced bone formation parameters in vivo, consistent with in vitro effects on osteoblast proliferation, differentiation, and survival. Compared with 17β-estradiol, which completely reversed the ovariectomy-induced increase in osteoclast number, cinaciguat had little effect on osteoclasts. Direct guanylate cyclase stimulators have been extremely well tolerated in clinical trials of cardiovascular diseases, and our findings provide proof-of-concept for this new class of drugs as a novel, anabolic treatment strategy for postmenopausal osteoporosis, confirming an important role of nitric oxide/cGMP/protein kinase G signaling in bone.

Rationale: Neurocognitive outcome after out-of-hospital cardiac arrest (OHCA) is often poor, even when initial resuscitation succeeds. Lower tidal volumes (VTs) attenuate extrapulmonary organ injury in other disease states and are neuroprotective in preclinical models of critical illness.Objective: To evaluate the association between VT and neurocognitive outcome after OHCA.Methods: We performed a propensity-adjusted analysis of a twocenter retrospective cohort of patients experiencing OHCA who received mechanical ventilation for at least the first 48 hours of hospitalization. VT was calculated as the time-weighted average over the first 48 hours, in milliliters per kilogram of predicted body weight (PBW). The primary endpoint was favorable neurocognitive outcome (cerebral performance category of 1 or 2) at discharge.Measurements and Main Results: Of 256 included patients, 38% received time-weighted average VT greater than 8 ml/kg PBW during the first 48 hours. Lower VT was independently associated with favorable neurocognitive outcome in propensityadjusted analysis (odds ratio, 1.61; 95% confidence interval [CI], 1.13-2.28 per 1-ml/kg PBW decrease in VT; P = 0.008). This finding was robust to several sensitivity analyses. Lower VT also was associated with more ventilator-free days (b = 1.78; 95% CI, 0.39-3.16 per 1-ml/kg PBW decrease; P = 0.012) and shockfree days (b = 1.31; 95% CI, 0.10-2.51; P = 0.034). VT was not associated with hypercapnia (P = 1.00). Although the propensity score incorporated several biologically relevant covariates, only height, weight, and admitting hospital were independent predictors of VT less than or equal to 8 ml/kg PBW.Conclusions: Lower VT after OHCA is independently associated with favorable neurocognitive outcome, more ventilator-free days, and more shock-free days. These findings suggest a role for low-VT ventilation after cardiac arrest.

Oral anticoagulation therapy is affected by the drug used, intensity of anticoagulation, physician's experience, patient compliance, laboratory testing and patient education. Patient education is a key factor in optimal anticoagulation and safety in patients on oral anticoagulant therapy. This study was done to assess the knowledge of patients regarding oral anticoagulant therapy in the outpatient setting. This prospective study was done over 2 months in 101 patients on outpatient oral anticoagulant therapy. A 20-point questionnaire on various aspects of oral anticoagulation therapy was administered to assess their knowledge. The answers were graded on a scale of 0-1. Scores were then added up to quantify the knowledge status in each patient. Descriptive statistics and Student's t test was used to analyse the data. The mean knowledge score among patients was 9.4/18 (52.2 %). More than half (52.8 %) of the patients had a score of <9. More than half (54.4 %) of the patients had adequate knowledge-(>80 % score-5.5/7) about the critical (must know) questions regarding OAT. Patients with age ≥60 years had lower mean scores compared to those <60 years of age (p = 0.028). Illiteracy was also associated (p < 0.0001) with poor scores. There are significant lacunae in the knowledge about oral anticoagulation among patients on outpatient treatment. Older age and illiteracy were associated with poor knowledge among patients. More emphasis needs to be given to the vital aspect of patient education to make this therapy safer for patients.