Rationale Exercise training confers sustainable protection against ischemia-reperfusion injury in animal models and has been associated with improved survival following a heart attack in humans. It is still unclear how exercise protects the heart, but it is apparent that endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) play a role. Objective To determine the role of β3-adrenergic receptors (β3-ARs), eNOS activation, and NO metabolites (nitrite and nitrosothiols) in the sustained cardioprotective effects of exercise Methods and Results Here we show that voluntary exercise reduces myocardial injury in mice following a 4-week training period and that these protective effects can be sustained for at least 1 week following the cessation of the training. The sustained cardioprotective effects of exercise are mediated by alterations in the phosphorylation status of eNOS (increase in serine 1177 and decrease in threonine 495) leading to an increase in NO generation and storage of NO metabolites (nitrite and nitrosothiols) in the heart. Further evidence revealed that the alterations in eNOS phosphorylation status and NO generation were mediated by β3-AR stimulation and that in response to exercise a deficiency of β3-ARs leads to an exacerbation of myocardial infarction following ischemia-reperfusion injury. Conclusions Our findings clearly demonstrate that exercise protects the heart against myocardial ischemia-reperfusion injury by stimulation of β3-ARs and increased cardiac storage of nitric oxide metabolites (i.e., nitrite and nitrosothiols).

Condit ME, Lefer DJ. The polysulfide diallyl trisulfide protects the ischemic myocardium by preservation of endogenous hydrogen sulfide and increasing nitric oxide bioavailability. Am J Physiol Heart Circ Physiol 302: H2410-H2418, 2012. First published March 30, 2012 doi:10.1152/ajpheart.00044.2012.-Diallyl trisulfide (DATS), a polysulfide constituent found in garlic oil, is capable of the release of hydrogen sulfide (H 2S). H2S is a known cardioprotective agent that protects the heart via antioxidant, antiapoptotic, anti-inflammatory, and mitochondrial actions. Here, we investigated DATS as a stable donor of H 2S during myocardial ischemiareperfusion (MI/R) injury in vivo. We investigated endogenous H 2S levels, infarct size, postischemic left ventricular function, mitochondrial respiration and coupling, endothelial nitric oxide (NO) synthase (eNOS) activation, and nuclear E2-related factor (Nrf2) translocation after DATS treatment. Mice were anesthetized and subjected to a surgical model of MI/R injury with and without DATS treatment (200 g/kg). Both circulating and myocardial H 2S levels were determined using chemiluminescent gas chromatography. Infarct size was measured after 45 min of ischemia and 24 h of reperfusion. Troponin I release was measured at 2, 4, and 24 h after reperfusion. Cardiac function was measured at baseline and 72 h after reperfusion by echocardiography. Cardiac mitochondria were isolated after MI/R, and mitochondrial respiration was investigated. NO metabolites, eNOS phosphorylation, and Nrf2 translocation were determined 30 min and 2 h after DATS administration. Myocardial H 2S levels markedly decreased after I/R injury but were rescued by DATS treatment (P Ͻ 0.05). DATS administration significantly reduced infarct size per area at risk and per left ventricular area compared with control (P Ͻ 0.001) as well as circulating troponin I levels at 4 and 24 h (P Ͻ 0.05). Myocardial contractile function was significantly better in DATS-treated hearts compared with vehicle treatment (P Ͻ 0.05) 72 h after reperfusion. DATS reduced mitochondrial respiration in a concentration-dependent manner and significantly improved mitochondrial coupling after reperfusion (P Ͻ 0.01). DATS activated eNOS (P Ͻ 0.05) and increased NO metabolites (P Ͻ 0.05). DATS did not appear to significantly induce the Nrf2 pathway. Taken together, these data suggest that DATS is a donor of H 2S that can be used as a cardioprotective agent to treat MI/R injury. cardioprotection; nitrite; left ventricular function; nitrosothiols; reperfusion injury; endothelial nitric oxide synthase

Objectives This paper examined whether nebivolol protects the heart via nitric oxide (NO) synthase and NO-dependent signaling in an in vivo model of acute myocardial infarction. Background Beta3-adrenergic receptor (AR) activation promotes endothelial nitric oxide synthase (eNOS) activity and NO bioavailability. We hypothesized that specific beta3-AR agonists would attenuate myocardial ischemia-reperfusion (MI/R) injury via eNOS activation and increased NO bioavailability. Methods Mice were subjected to 45 min of myocardial ischemia in vivo followed by 24 h of reperfusion (R). Nebivolol (500 ng/kg), CL 316243 (1 μg/kg), BRL-37344 (1 μg/kg), or vehicle (VEH) was administered at the time of R. Myocardial area-at-risk (AAR) and infarct size (INF)/AAR was measured at 24 h of R. Cardiac tissue and plasma were collected to evaluate eNOS phosphorylation, neuronal nitric oxide synthase (nNOS), inducible nitric oxide synthase expression, and nitrite and nitrosothiol levels. Results Nebivolol (500 ng/kg) reduced INF/AAR by 37% (p < 0.001 vs. VEH) and serum troponin-I levels from 41 ± 4 ng/ml to 25 ± 4 ng/ml (p < 0.05 vs. VEH). CL 316243 and BRL-37344 reduced INF by 39% and 42%, respectively (p < 0.001 vs. VEH). Nebivolol and CL 316243 increased eNOS phosphorylation at Ser-1177 (p < 0.05 vs. VEH) and increased nitrite and total nitrosylated protein levels. Nebivolol and CL 316243 significantly increased myocardial nNOS expression. Nebivolol failed to reduce INF after MI/R in beta3-AR−/−, eNOS−/−, and in nNOS−/− mice. Conclusions Our results indicate that beta3-AR agonists protect against MI/R injury. Furthermore, the cardioprotective effects of beta3-AR agonists are mediated by rapid eNOS and nNOS activation and increased NO bioavailability.

The likely vector was Amblyomma triste, a Neotropical tick species only recently recognized in the United States.

Objective β2-adrenoreceptor activation has been shown to protect cardiac myocytes from cell death. We hypothesized that acute β2-adrenoreceptor stimulation, using arformoterol (ARF), would attenuate myocardial ischemia/reperfusion (R) injury via NO synthase activation and cause a subsequent increase in NO bioavailability. Methods and Results Male C57BL/6J and endothelial NO synthase (eNOS) knockout mice were subjected to 45 minutes of myocardial ischemia and 24 hours of R. ARF or vehicle was administered 5 minutes before R. Serum troponin-I was measured, and infarct size per area-at-risk was evaluated at 24 hours of R. Echocardiography was performed at baseline and 2 weeks after R. Myocardial cAMP, protein kinase A, eNOS/Akt phosphorylation status, and NO metabolite levels were assayed. ARF (1 μg/kg) reduced infarct size per area-at-risk by 53.1% (P<0.001 versus vehicle) and significantly reduced troponin-I levels (P<0.001 versus vehicle). Ejection fraction was significantly preserved in ARF-treated hearts compared with vehicle hearts at 2 weeks of R. Serum cAMP and nuclear protein kinase A C-α increased 5 and 15 minutes after ARF injection, respectively (P<0.01). ARF increased Akt phosphorylation at Thr308 (P<0.001) and Ser473 (P<0.01), and eNOS phosphorylation at Ser1177 (P<0.01). ARF treatment increased heart nitrosothiol levels (P<0.001) at 15 min after injection. ARF failed to reduce infarct size in eNOS−/− mice. Conclusions Our results indicate that β2-adrenoreceptor stimulation activates cAMP, protein kinase A, Akt, and eNOS and augments NO bioavailability. Activation of this prosurvival signaling pathway attenuates myocardial cell death and preserves cardiac function after ischemia/reperfusion.

Background Since 2000, the reported prevalence of tick-borne spotted fever rickettsiosis has increased considerably. We compared the level of antibody reactivity among healthy blood donors from 2 widely separated regions of the United States and evaluated the impact of antibody prevalence on public health surveillance in one of these regions. Methods Donor serum samples were evaluated by indirect immunofluorescence antibody assay to identify immunoglobulin G (IgG) antibodies reactive with Rickettsia rickettsii. The Georgia Department of Public Health (GDPH) analyzed characteristics of cases from 2016 surveillance data to evaluate the utility of laboratory surveillance for case assessment. Results Of the Georgia donors (n = 1493), 11.1% demonstrated antibody titers reactive with R. rickettsii at titers ≥64, whereas 6.3% of donors from Oregon and Washington (n = 1511) were seropositive. Most seropositive donors had a titer of 64; only 3.1% (n = 93) of all donors had titers ≥128. During 2016, GDPH interviewed 243 seropositive case patients; only 28% (n = 69) met inclusion criteria in the national case definition for spotted fever rickettsiosis. Conclusions These findings suggest that a single IgG antibody titer is an unreliable measure of diagnosis and could inaccurately affect surveillance estimates that define magnitude and clinical characteristics of Rocky Mountain spotted fever and other spotted fever rickettsioses.

During 2012-2014, five cases of Rickettsia parkeri rickettsiosis were identified by a single urgent care practice in Georgia, located approximately 40 miles southwest of Atlanta. Symptom onset occurred during June-October, and all patients had a known tick bite. Patients ranged in age from 27 to 72 years (median = 53 years), and all were male. The most commonly reported initial signs were erythema (n = 3) and swelling (n = 2) at the site of the bite. Two patients reported fever and a third patient reported a rash and lymphadenopathy without fever. Other symptoms included myalgia (n = 3), chills (n = 3), fatigue (n = 2), arthralgia (n = 2), and headache (n = 2). Eschar biopsy specimens were collected from each patient using a 4-mm or 5-mm punch and placed in 10% neutral buffered formalin or sterile saline. These specimens were tested by immunohistochemical (IHC) stains, quantitative polymerase chain reaction (qPCR) assays, or cell culture isolation to determine if there was evidence of infection with a Rickettsia species (1). IHC evidence of spotted fever group rickettsiae was found in the eschar biopsy specimens in all five cases. In four cases, the biopsy specimens were also positive for R. parkeri by qPCR. The fifth case (specimen positive only by IHC testing) was considered a probable R. parkeri case based on clinical signs and symptoms. R. parkeri was grown in cell culture from one specimen from which isolation was attempted. All patients were treated with oral doxycycline (100 mg twice daily) for a minimum of 10 days, and all recovered.

African tick bite fever is the most commonly encountered travel-associated rickettsiosis, occurring in as many as 5% of travelers returning from rural subequatorial Africa. This case report illustrates that rifampin represents an effective alternative to doxycycline for treatment of African tick bite fever in some selective situations.