Hemodynamic responses to acute carboxyhemoglobinemia in the rat

Update on prevalence and distribution pattern of tick-borne diseases among humans in India: a review

In the present scenario, tick-borne diseases (TBDs) are well known for their negative impacts on humans as well as animal health in India. The reason lies in their increased incidences due to global warming, environmental and ecological changes, and availability of suitable habitats. On a global basis, they are now considered a serious threat to human as well as livestock health. The major tick-borne diseases in India include Kyasanur forest disease (KFD), Crimean-congo hemorrhagic fever (CCHF), Lyme disease (LD), Q fever (also known as coxiellosis), and Rickettsial infections. In recent years, other tick-borne diseases such as Babesiosis, Ganjam virus (GANV), and Bhanja virus (BHAV) infections have also been reported in India. The purpose of this paper is to review the history and the current state of knowledge of tick-borne diseases in the country. The conclusion of this review is extending the requirement of greater efforts in research and government management for the diagnosis and treatment and as well as prevention of these diseases so that tick-borne disease burden should be minimizing in India.

Short-term effects of air pollution on blood pressure

Elevated blood pressure (BP) has been proposed as a possible pathophysiological mechanism linking exposure to ambient air pollution and the increased risk of cardiovascular mortality and morbidity. In this study, we investigated the hourly relationship between ambient air pollutants and BP. BP measurements were extracted from the electronic health record database of the Seoul National University Bundang Hospital from February 2015 to June 2017. A total of 98,577 individual BP measurements were matched to the hourly levels of air pollutants. A generalized additive model was constructed for hour lags of 0–8 of air pollutants adjusting for age, sex, meteorological variables, and time trend. Systolic BP was shown to be significantly lower at 2–4 hours and 3–5 hours after increased levels of SO₂ and CO, respectively (0.24 mmHg and 0.26 mmHg for an interquartile range, respectively). In contrast, O₃ and NO₂ were associated with significantly increased systolic BP at 3–5 lag hours and at 0–2 lag hours, respectively. BP elevation in association with O₃ and NO₂ was shown to be significantly greater in hypertensive patients than normotensive subjects. Our findings suggest that short-term exposure to air pollution may be associated with elevated BP.

Myocardial dysfunction and potential cardiac hypoxia in rats induced by carbon monoxide inhalation

BACKGROUND

Results from both animal and human being studies provide evidence that inhalation of concentrations of carbon monoxide (CO) at around 100 ppm has antiinflammatory effects. These low levels of CO are incriminated in ischemic heart diseases experienced by cigarette smokers and, in some cases, from air pollution. Although neurologic mechanisms have been investigated, the effects of CO on cardiovascular function are still poorly understood.

METHODS AND RESULTS

The effects of CO (250 ppm; 90 min) inhalation on myocardial function were investigated in isolated heart of rats killed immediately, and 3, 24, 48, and 96 h after CO exposure. CO exposure at 250 ppm resulted in an arterial carboxyhemoglobin (HbCO) level of approximately 11%, which was not associated with changes in mean arterial pressure and heart rate. CO exposure induced coronary perfusion pressure increases, which were associated with endothelium-dependent and -independent vascular relaxation abnormalities. CO-induced coronary vascular relaxation perturbations were observed in the presence of increased heart contractility. Spontaneous peak to maximal Ca(2+)-activated left ventricular pressure ratio was markedly increased in CO-exposed rats, indicating increases in myofilament calcium sensitivity. Heart cyclic guanosine monophosphate/cAMP ratio and myocardial permeabilized fiber respiration (complex intravenous activity) were reduced in CO-exposed rats, which lasted after 48 h of reoxygenation in air.

CONCLUSIONS

These findings suggest that CO deteriorates heart oxygen supply to utilization and potentially may induce myocardial hypoxia through mechanisms that include increased oxygen demand due to increased contractility, reduced coronary blood flow reserve, and cardiomyocyte respiration inhibition.

Carbon monoxide attenuates aeroallergen-induced inflammation in mice

Carbon monoxide (CO) generated by catalysis of heme by heme oxygenase is increased in the exhaled air of asthmatic patients. Based on recent studies demonstrating that asthma is an inflammatory disease associated with increased oxidants and that CO confers cytoprotection in oxidant-induced lung injury and inflammation, we sought to better understand the functional role of CO in asthma by using an aeroallergen model. Mice were sensitized to ovalbumin, challenged with aerosolized ovalbumin, and maintained in either CO (250 parts/million) or room air for 48 h. The differential effects of CO on bronchoalveolar lavage (BAL) fluid cell types were observed, with a marked attenuation of BAL fluid eosinophils in the CO-treated animals at 24 and 48 h. A marked reduction of the proinflammatory cytokine interleukin-5 was observed in the CO-treated mice, with no significant changes for other proinflammatory cytokines. These differential effects of CO were also observed with leukotrienes (LTs) and prostaglandins in that CO significantly decreased BAL fluid PGE2, and LTB4 but exerted negligible effect on thromboxane B2 or LTC4/D4/E4. Our data suggest a putative immunoregulatory role for CO in aeroallergen-induced inflammation in mice.

Exercising skeletal muscle blood flow in humans responds to reduction in arterial oxyhaemoglobin, but not to altered free oxygen

We hypothesised that reducing arterial oxyhaemoglobin (O2Hba) with carbon monoxide (CO) in both normoxia and hyperoxia, or acute hypoxia would cause similar compensatory increases in human skeletal muscle blood flow and vascular conductance during submaximal exercise, despite vast differences in arterial free oxygen partial pressure (Pa,O2). Seven healthy males completed four 5 min one-legged knee-extensor exercise bouts in the semi-supine position (30 +/- 3 W, mean +/- S.E.M.), separated by approximately 1 h of rest, under the following conditions: (a) normoxia (O2Hba = 195 ml l-1; Pa,O2 = 105 mmHg); (b) hypoxia (163 ml l-1; 47 mmHg); (c) CO + normoxia (18% COHba; 159 ml l-1; 119 mmHg); and (d) CO + hyperoxia (19% COHba; 158 ml l-1; 538 mmHg). CO + normoxia, CO + hyperoxia and systemic hypoxia resulted in a 29-44% higher leg blood flow and leg vascular conductance compared to normoxia (P < 0.05), without altering blood pH, blood acid-base balance or net leg lactate release. Leg blood flow and leg vascular conductance increased in association with reduced O2Hba (r2 = 0.92-0.95; P < 0.05), yet were unrelated to altered Pa,O2. This association was further substantiated in two subsequent studies with graded increases in COHba (n = 4) and NO synthase blockade (n = 2) in the presence of normal Pa,O2. The elevated leg blood flow with CO + normoxia and CO + hyperoxia allowed a approximately 17% greater O2 delivery (P < 0.05) to exercising muscles, compensating for the lower leg O2 extraction (61%) compared to normoxia and hypoxia (69%; P < 0.05), and thereby maintaining leg oxygen uptake constant. The compensatory increases in skeletal muscle blood flow and vascular conductance during exercise with both a CO load and systemic hypoxia are independent of pronounced alterations in Pa,O2 (47-538 mmHg), but are closely associated with reductions in O2Hba. These results suggest a pivotal role of O2 bound to haemoglobin in increasing skeletal muscle vasodilatation during exercise in humans.