Single-night continuous positive airway pressure treatment improves blood fluid properties in individuals recently diagnosed with obstructive sleep apnoea.

Obstructive sleep apnoea (OSA) is a prevalent disorder that causes repetitive, temporary collapses of the upper airways during sleep, resulting in intermittent hypoxaemia and sleep fragmentation. Given those with OSA also exhibit decreased blood fluidity, this clinical population is at heightened risk for cardiovascular disease (CVD) development. Continuous positive airway pressure (CPAP) remains a primary therapy in OSA, which improves sleep quality and limits sleep fragmentation. While CPAP effectively ameliorates nocturnal hypoxic events and associated arousals, it remains unclear whether CVD risk factors are positively impacted. The aim of the present study was thus to assess the effects of an acute CPAP therapy on sleep quality and the physical properties of blood that determine blood fluidity. Sixteen participants with suspected OSA were recruited into the current study. Participants attended the sleep laboratory for two visits: an initial diagnostic visit that included confirmation of OSA severity and comprehensive assessments of blood parameters, followed by a subsequent visit where participants were administered an individualised, acute CPAP therapy session and had their blood assessments repeated. Holistic appraisal of blood rheological properties included assessment of blood and plasma viscosity, red blood cell (RBC) aggregation, deformability, and osmotic gradient ektacytometry. Acute CPAP treatment significantly improved sleep quality parameters, which were associated with decreased nocturnal arousals and improved blood oxygen saturation. Whole blood viscosity was significantly decreased following acute CPAP treatment, which might be explained by the improved RBC aggregation during this visit. Although an acute increase in plasma viscosity was observed, it appears that the alterations in RBC properties that mediate cell-cell aggregation, and thus blood viscosity, overcame the increased plasma viscosity. While deformability of RBC was unaltered, CPAP therapy had mild effects on the osmotic tolerance of RBC. Collectively, novel observations demonstrate that a single CPAP treatment session acutely improved sleep quality, which was accompanied by improved rheological properties.

Accurate prediction of drug-induced heterogeneous response of red cell in vivo using a gravity-driven flow cytometry based on a microfluidic chip.

The drug-induced diverse response among patients is a severe problem for improving hemorheological character. However, there is no validated method for personalized therapy to the best of our knowledge. Here, we apply a gravity-driven deformability cytometry platform (GD-DCP) to profile the drug response of the red cell deformability (RCD) at the single-cell level using pentoxifylline (PTX) as a model drug, the effect of different concentrations of PTX (0, 2, 20, 200 µg mL-1, the clinical dosage of PTX is 20 µg mL-1) on RCD in patients with cardiovascular disease was explored. Based on the GD-DCP, about 38 and 56% of the acute phase of acute myocardial infarction (AMI) patients in the acute phase and coronary heart disease (CHD) patients respond positively to PTX, respectively, indicating that PTX has a strong patient dependency on RCD. Moreover, RCD is observed to be significantly inversely correlated with the activation of membrane protein kinase C (PKC) as well as the concentration of Ca2+ (both P < 0.001). The results of animal experiments show that the protective effects of PTX on myocardial ischemia rats have substantial individual variation, too. It is noted that the effect of PTX is highly consistent between RCD in vitro and in vivo outcomes (blood viscosity, myocardial injury, and electrocardiogram (ECG)) in the same rat. All these new findings suggest that the GD-DCP is a promising method that uses deformability in vitro as one of the important criteria in personalized medicine, and our study provides unique insight into the individual-dependent mechanisms of PTX for improving RCD.

Knowlesi malaria: Human risk factors, clinical spectrum, and pathophysiology.

Plasmodium knowlesi is endemic across Southeast Asia, and is the commonest cause of zoonotic malaria. The spectrum of clinical disease from P. knowlesi infection ranges from asymptomatic infection, through to severe malaria and death. Over 90% of clinical disease occurs in adults, mostly living in forest edge areas undergoing intensive land use change. With a 24-h asexual life cycle in humans, high parasite counts are possible, but most clinical cases of knowlesi malaria are uncomplicated with low parasitaemia. In co-endemic areas, median parasitaemia in knowlesi malaria is lower than that seen in vivax and falciparum malaria, suggesting a lower fever threshold. Severe malaria occurs in 6-9% of symptomatic adults. Manifestations of severe malaria from P. knowlesi are similar to those seen with falciparum malaria, with the notable absence of coma. Age, parasitaemia, cardiovascular comorbidities and delayed diagnosis are risk factors for severe disease and death, which are only seen in adults. Thrombocytopenia is near-universal in adults, likely related to platelet-red cell binding and clearance. Mechanisms underlying the microvascular sludging seen in fatal disease in non-natural primate hosts and the microvascular accumulation of parasites in fatal human disease are not clear. Marked reductions in deformability of both infected and uninfected red blood cells are associated with disease severity in both humans and other non-natural primate hosts, likely contributing to impaired microvascular perfusion and organ dysfunction. Endothelial activation, endothelial dysfunction, glycocalyx degradation and haemolysis are also associated with, and likely contribute to, severe disease and organ dysfunction, particularly acute kidney injury.

How Do Red Blood Cells Die?

Normal human red blood cells have an average life span of about 120 days in the circulation after which they are engulfed by macrophages. This is an extremely efficient process as macrophages phagocytose about 5 million erythrocytes every second without any significant release of hemoglobin in the circulation. Despite large number of investigations, the precise molecular mechanism by which macrophages recognize senescent red blood cells for clearance remains elusive. Red cells undergo several physicochemical changes as they age in the circulation. Several of these changes have been proposed as a recognition tag for macrophages. Most prevalent hypotheses for red cell clearance mechanism(s) are expression of neoantigens on red cell surface, exposure phosphatidylserine and decreased deformability. While there is some correlation between these changes with aging their causal role for red cell clearance has not been established. Despite plethora of investigations, we still have incomplete understanding of the molecular details of red cell clearance. In this review, we have reviewed the recent data on clearance of senescent red cells. We anticipate recent progresses in in vivo red cell labeling and the explosion of modern proteomic techniques will, in near future, facilitate our understanding of red cell senescence and their destruction.

Cross-sectional distributions of normal and abnormal red blood cells in capillary tubes determined by a new technique.

BACKGROUND: In the microcirculation, red blood cells (RBCs) were observed to be confined to an axial stream surrounded by a marginal RBC depleted layer. This axial accumulation of RBCs is considered to arise from the RBC deformability. OBJECTIVE: To quantitatively evaluate the effect of RBC deformability on their axial accumulation at a flow condition comparable to that in arterioles by developing a new observation system for accurate measurements of radial RBC positions in the cross section of capillary tubes. METHODS: The cross-sectional distributions of normal and hardened RBCs as well as softened RBCs suspended in capillary tube flows were measured with high spatial resolution. A new observation system was developed in which enface views of the cross-section of the tube were obtained at small distances upstream of the outlet at various longitudinal positions in the tube. RESULTS: The radial positions of individual RBCs were detected within 1 µm accuracy. It was found that normal and softened RBCs rapidly migrated away from the wall towards the tube axis, whereas glutaraldehyde-hardened RBCs were dispersed widely over the tube cross-section, depending on the concentration of glutaraldehyde solution. CONCLUSIONS: The newly devised observation system revealed quantitatively the essential role of RBC deformability in their axial accumulation.

Detrimental effects of niacin/laropiprant on microvascular reactivity and red cell deformability in patients with elevated lipoprotein(a) levels.

Several studies have found a beneficial effect of nicotinic acid on lipid profile, but there remains a limitation in the clinical use of nicotinic acid due to its side effects. In this study, 46 (F/M = 22/24, age = 58.74 ± 10.02 years) patients with Lp(a) ≥500 mg/L and with a previous arterial thrombotic event were treated with nicotinic acid/laropiprant (Tredaptive®). We found a significant reduction in the Lp(a) values at T1 (after 12 months), with a decrease of 32.3 % from baseline levels. At T1, 11 patients (23.9 %) showed Lp(a) levels to be <500 mg/L. PAT values were significantly decreased after treatment (2.13 ± 0.81 vs 1.74 ± 0.42, p = 0.001), showing a worsening of endothelial function in 27 (58.6 %) patients. A significantly higher number of patients had RHI <1.5 after the treatment [18 (39.1 %) vs 8 (17.4 %)]. Blood rheology worsened as ED was impaired (p < 0.0001) after 12 months, whereas WHV, plasma viscosity, and red cell aggregation did not show any significant differences in comparison to baseline. Patients with a worsening in microvascular reactivity in comparison to baseline showed a marked impairment in ED (0.3327 ± 0.037 vs 0.3091 ± 0.0351; p < 0.0001), while others showed only a mild, even though significant, reduction (0.3347 ± 0.0299 vs 0.3272 ± 0.0235; p = 0.044). In the light of the results of HPS2-THRIVE study, we may hypothesize that the addition of laropiprant to niacin might be responsible for these negative effects. In turn, these effects might explain, at least in part, the lack of a clinical net benefit of niacin/laropiprant in the trial.

Influence of endurance training and marathon running on red cell deformability in HIV patients.

PURPOSE: This investigation assessed whether endurance training altered the red cell deformability (RCD) of male HIV patients. METHODS: Eight subjects (38 ± 9 years, BMI 23 ± 3.6 kg/m², highly active antiretroviral therapy) trained for a marathon run for the duration of one year. Each subject underwent an acute exercise test on a treadmill at the beginning of this study (baseline) and after four months of training. Blood samples were taken at rest (T0) and at the end (T1) of each exercise test, as well as before (T0) and after the marathon run (T1). RCD was measured using the Laser Assisted Optical Rotational Cell Analyzer (LORCA), the maximal elongation index (EImax) and shear stress at half maximal deformation (SS ½ were determined using the Lineweaver Burke model. RESULTS: No changes were observed in RCD and SS ½ between T0 and T1 in all measurements. EImax significantly increased between T0 baseline and T0 after four months of training (P < 0.05). Measurements prior to the marathon run revealed significantly decreased EImax and SS ½ values (P < 0.05). CONCLUSIONS: The intensity of training in pathophysiological diseases like HIV is dependent for the alterations in RCD and possible improvements in microcirculation.