Effect of diabetic duration on hemorheological properties and platelet aggregation in streptozotocin-induced diabetic rats

Investigation of Zinc on hemorheological parameters in a rat model of diabetes

Diabetes mellitus (DM) is a complex, chronic metabolic disorder characterized by impaired regulation of blood glucose levels. Zinc (Zn) is an essential trace elements that plays a role in various physiological processes within the body, including those related to diabetes. The current study was investigated the effect of Zn supplementation on hemorheological parameters in a rat model of DM. After induction of DM, 32 male Wistar albino rats were divided into four groups: control, Zn, DM, and Zn+DM. Whole blood viscosity (WBV) was determined by using digital cone and plate viscometer and plasma viscosity (PV) was determined by a Coulter Harkness capillary viscometer. The rats in the DM Group showed a decrease in both Zn levels and body weight, as well as an increase in glucose levels when compared to the control group. Diabetic rats supplemented with Zn displayed lower blood glucose levels and higher concentrations of Zn compared to the DM Group. The higher PV and lower hematocrit level were measured in DM Group than control group and lower PV, higher hematocrit level were measured in Zn+DM group than DM Group. The WBV was measured at four different shear rates (57.6-115.2 - 172.8-230.4 s -1). A statistically significant increase was observed in the DM group compared to the control group. Additionally, a statistically significant decrease was observed in the Zn+DM Group compared to the DM Group at a shear rate of 230.4 s-1. Erythrocyte rigidity index (Tk) and oxygen delivery index (ODI) were computed under conditions of high shear rate. The rats in the DM group exhibited a reduction in ODI and an elevation in Tk in comparison to the control group. Conversely, the diabetic rats supplemented with Zn exhibited decreased Tk and increased ODI compared to the DM Group. Zn supplementation seems to have a potential beneficial effect for protecting adverse affect of diabetes on hemorheogical parameters and for maintaining vascular health.

Duration of the diabetic state altered platelet indices from baseline values in a streptozotocin-induced rat model for type 1 diabetes mellitus

BACKGROUND

Changes in platelet indices in naturally occurring type I diabetes mellitus (T1DM) have been described in several studies. In this study, platelet indices such as platelet count (PLT), plateletcrit (PCT), mean platelet volume (MPV), platelet distribution width (PDW), and MPV to PLT ratio were investigated according to diabetic duration after streptozotocin (STZ)-induced T1DM, as well as for their correlation with glucose.

METHODS

Forty healthy adult Wistar rats were randomly assigned to four experimental groups of ten (5 rats of each sex), including the control group, the 7, 14, and 28 days diabetic groups (D7, D14, and D28, respectively).

RESULTS

In diabetic groups, plasma glucose was significantly higher than in control (P < 0.01). D7, D14, and D28 groups presented significantly lower PLT than the control (P < 0. 01). A significant decrease in PCT was observed in D14 and D28 females (P < 0.05). Mean platelet volume was significantly higher in the D28 group than in to control. D28 females also showed a significant difference in PLT, MPV, and the MPV-to-PLT ratio compared with D7 females (P < 0.05). A comparison between D28 females and males showed a significant difference in PDW (P < 0.05). Both females and males showed a significant correlation between glucose and PLT, PCT, MPV, and the MPV-to-PLT ratio.

CONCLUSIONS

Platelet indices change significantly with the duration of diabetes compared with the baseline values, and female and male rats did not have significant differences in platelet indices in any period except the 28 days.

Recent advances of the nanocomposite hydrogel as a local drug delivery for diabetic ulcers

Diabetic ulcer is a serious complication of diabetes. Compared with that of healthy people, the skin of patients with a diabetic ulcer is more easily damaged and difficult to heal. Without early intervention, the disease will become increasingly serious, often leading to amputation or even death. Most current treatment methods cannot achieve a good wound healing effect. Numerous studies have shown that a nanocomposite hydrogel serves as an ideal drug delivery method to promote the healing of a diabetic ulcer because of its better drug loading capacity and stability. Nanocomposite hydrogels can be loaded with one or more drugs for application to chronic ulcer wounds to promote rapid wound healing. Therefore, this paper reviews the latest progress of delivery systems based on nanocomposite hydrogels in promoting diabetic ulcer healing. Through a review of the recent literature, we put forward the shortcomings and improvement strategies of nanocomposite hydrogels in the treatment of diabetic ulcers.

Contributions of Red Blood Cell Sedimentation in a Driving Syringe to Blood Flow in Capillary Channels

The erythrocyte sedimentation rate (ESR), which has been commonly used to detect physiological and pathological diseases in clinical settings, has been quantified using an interface in a vertical tube. However, previous methods do not provide biophysical information on blood during the ESR test. Therefore, it is necessary to quantify the individual contributions in terms of viscosity and pressure. In this study, to quantify RBC sedimentation, the image intensity (Ib) and interface (β) were obtained by analyzing the blood flow in the microfluidic channels. Based on threshold image intensity, the corresponding interfaces of RBCs (Ib > 0.15) and diluent (Ib < 0.15) were employed to obtain the viscosities (µb, µ0) and junction pressures (Pb, P0). Two coefficients (CH1, CH2) obtained from the empirical formulas (µb = µ0 [1 + CH1], Pb = P0 [1 + CH2]) were calculated to quantify RBC sedimentation. The present method was then adopted to detect differences in RBC sedimentation for various suspended blood samples (healthy RBCs suspended in dextran solutions or plasma). Based on the experimental results, four parameters (µ0, P0, CH1, and CH2) are considered to be effective for quantifying the contributions of the hematocrit and diluent. Two coefficients exhibited more consistent trends than the conventional ESR method. In conclusion, the proposed method can effectively detect RBC sedimentation.

Blood rheometer based on microflow manipulation of continuous blood flows using push-and-back mechanism

To understand the contributions of rheological properties to microcirculation, the simultaneous measurement of multiple rheological properties under continuous blood flows has been emphasized. However, existing methods exhibit limitations in terms of continuous and simultaneous monitoring. In this study, a simple method is suggested for simultaneously measuring four rheological properties (i.e., red blood cell (RBC) aggregation, blood viscosity, blood junction pressure, and RBC sedimentation) under a continuous blood flow. Using the push-and-back mechanism, which comprises a co-flowing channel, a test chamber, and an air compliance unit (ACU), blood is supplied to the test chamber and restored into the co-flowing channel periodically and reversely. First, RBC aggregation is quantified based on the intensity of the blood image in the test chamber. Second, blood viscosity and blood junction pressure are determined by analyzing the interface in the co-flowing channel. Lastly, RBC sedimentation is evaluated by analyzing the intensity of the blood image in the blood chamber. Based on quantitative studies involving several vital factors, the tubing length of ACU is set to L = 30 mm. The reference fluid (glycerin [20%]) is controlled in a periodic on-off manner (period = 240 s, and flow rate = 1 mL h^-1). The blood flow rate is maintained at 1 mL h^-1. Subsequently, the present method is used to determine the rheological properties of several blood samples with different hematocrits or diluents. Compared with previous studies, the present method yields sufficiently consistent trends with respect to the hematocrit level or concentration of dextran solution. The experimental results imply that the present method enables simultaneous and consistent measurements of four rheological properties of blood under continuous blood flows. This method can be regarded as a promising method for monitoring multiple rheological properties of blood circulating under an in vitro closed fluidic circuit.

Integrating blood cell mechanics, platelet adhesive dynamics and coagulation cascade for modelling thrombus formation in normal and diabetic blood

Normal haemostasis is an important physiological mechanism that prevents excessive bleeding during trauma, whereas the pathological thrombosis especially in diabetics leads to increased incidence of heart attacks and strokes as well as peripheral vascular events. In this work, we propose a new multiscale framework that integrates seamlessly four key components of blood clotting, namely transport of coagulation factors, coagulation kinetics, blood cell mechanics and platelet adhesive dynamics, to model the development of thrombi under physiological and pathological conditions. We implement this framework to simulate platelet adhesion due to the exposure of tissue factor in a three-dimensional microchannel. Our results show that our model can simulate thrombin-mediated platelet activation in the flowing blood, resulting in platelet adhesion to the injury site of the channel wall. Furthermore, we simulate platelet adhesion in diabetic blood, and our results show that both the pathological alterations in the biomechanics of blood cells and changes in the amount of coagulation factors contribute to the excessive platelet adhesion and aggregation in diabetic blood. Taken together, this new framework can be used to probe synergistic mechanisms of thrombus formation under physiological and pathological conditions, and open new directions in modelling complex biological problems that involve several multiscale processes.

Effects of Diabetes on Microcirculation and Leukostasis in Retinal and Non-Ocular Tissues: Implications for Diabetic Retinopathy

Changes in retinal microcirculation are associated with the development of diabetic retinopathy (DR). However, it is unclear whether such changes also develop in capillary beds of other non-retinal tissues. Here, we investigated microcirculatory changes involving velocity of rolling neutrophils, adherence of neutrophils, and leukostasis during development of retinal vascular lesions in diabetes in other non-retinal tissues. Intravital microscopy was performed on post-capillary venules of cremaster muscle and ear lobe of mice with severe or moderate diabetes and compared to those of non-diabetic mice. Additionally, number and velocity of rolling leukocytes, number of adherent leukocytes, and areas of leukostasis were quantified, and retinal capillary networks were examined for acellular capillaries (AC) and pericyte loss (PL), two prominent vascular lesions characteristic of DR. The number of adherent neutrophils and areas of leukostasis in the cremaster and ear lobe post-capillary venules of diabetic mice was increased compared to those of non-diabetic mice. Similarly, a significant increase in the number of rolling neutrophils and decrease in their rolling velocities compared to those of non-diabetic control mice were observed and severity of diabetes exacerbated these changes. Understanding diabetes-induced microcirculatory changes in cremaster and ear lobe may provide insight into retinal vascular lesion development in DR.

Microfluidic Quantification of Blood Pressure and Compliance Properties Using Velocity Fields under Periodic On–Off Blood Flows

To monitor variations of blood samples effectively, it is required to quantify static and dynamic properties simultaneously. With previous approaches, the viscosity and elasticity of blood samples are obtained for static and transient flows with two syringe pumps. In this study, simultaneous measurement of pressure and equivalent compliance is suggested by analyzing the velocity fields of blood flows, where a blood sample is delivered in a periodic on-off fashion with a single syringe pump. The microfluidic device is composed of a main channel (mc) for quantifying the equivalent compliance and a pressure channel (pc) for measuring the blood pressure. Based on the mathematical relation, blood pressure at junction (Px) is expressed as Px = kβ. Here, β is calculated by integrating the averaged velocity in the pressure channel (<Upc>). The equivalent compliance (Ceq) is then quantified as Ceq = λoff · Q0/Px with a discrete fluidic model. The time constant (λoff ) is obtained from the transient behavior of the averaged blood velocity in the main channel (<Umc>). According to results, Px and Ceq varied considerably with respect to the hematocrit and flow rate. The present method (i.e., blood pressure, compliance) shows a strong correlation with the previous method (i.e., blood viscosity, elasticity). In conclusion, the present method can be considered as a potential tool for monitoring the mechanical properties of blood samples supplied periodically from a single syringe pump.

Blood Viscoelasticity Measurement Using Interface Variations in Coflowing Streams under Pulsatile Blood Flows

Blood flows in microcirculation are determined by the mechanical properties of blood samples, which have been used to screen the status or progress of diseases. To achieve this, it is necessary to measure the viscoelasticity of blood samples under a pulsatile blood condition. In this study, viscoelasticity measurement is demonstrated by quantifying interface variations in coflowing streams. To demonstrate the present method, a T-shaped microfluidic device is designed to have two inlets (a, b), one outlet (a), two guiding channels (blood sample channel, reference fluid channel), and one coflowing channel. Two syringe pumps are employed to infuse a blood sample at a sinusoidal flow rate. The reference fluid is supplied at a constant flow rate. Using a discrete fluidic circuit model, a first-order linear differential equation for the interface is derived by including two approximate factors (F₁ = 1.094, F₂ = 1.1087). The viscosity and compliance are derived analytically as viscoelasticity. The experimental results showed that compliance is influenced substantially by the period. The hematocrit and diluent contributed to the varying viscosity and compliance. The viscoelasticity varied substantially for red blood cells fixed with higher concentrations of glutaraldehyde solution. The experimental results showed that the present method has the ability to monitor the viscoelasticity of blood samples under a sinusoidal flow-rate pattern.

Type 2 diabetes differentially affects the substrate saturation kinetic attributes of erythrocyte hexokinase and phosphofructokinase

The substrate kinetic parameters of hexokinase (HK) and phosphofructokinase (PFK)-the key irreversible enzymes of glycolysis-in erythrocytes from type 2 diabetic subjects were examined in comparison with control subjects. It was observed that the kinetic parameters such as K_m , V_max , Apparent K_cat , K_cat /K_m , and substrate (ATP) inhibition kinetic and substrate binding characteristics are significantly altered in the diabetic group. The observed changes are suggestive of compositional changes in the subunit makeup of HK and PFK. The implication of these findings in relation to energy status of the diabetic erythrocyte and its interrelationship with loss of cell deformability are discussed here.

Altered function and expression of the orphan GPR135 at the cardiovascular level in diabetic Wistar rats

Cardiovascular complications are the main cause of mortality in patients with diabetes, these have been associated with changes in function and expression of receptors coupled to G proteins (GPCR), which include orphan receptors which some of them tend to modify in diabetes, although others are not known, such as GPR135. For this reason, the objective of this work was to study the expression of the orphan receptor GPR135 in brain, heart, kidney, aorta, lung, spleen and liver of diabetic rats, as well as its function by the administration of siRNA (small interfering RNA) and curves to isoproterenol. Our results showed that GPR135 is expressed in all tissues analyzed and its expression is modified due to diabetes, we also observed that the responses to isoproterenol increase in diabetic rats administered with siRNA. Therefore, we conclude that the orphan receptor GPR135 is expressed in different tissues and its expression tends to be modified due to diabetes, besides that it is functional and that it seems to be coupled to Gi/o protein which has negative chronotropic and inotropic effects, therefore, we do not rule out that it participates in the cardiovascular complications associated with diabetes.

Microfluidic-Based Biosensor for Sequential Measurement of Blood Pressure and RBC Aggregation Over Continuously Varying Blood Flows

Aggregation of red blood cells (RBCs) varies substantially depending on changes of several factors such as hematocrit, membrane deformability, and plasma proteins. Among these factors, hematocrit has a strong influence on the aggregation of RBCs. Thus, while measuring RBCs aggregation, it is necessary to monitor hematocrit or, additionally, the effect of hematocrit (i.e., blood viscosity or pressure). In this study, the sequential measurement method of pressure and RBC aggregation is proposed by quantifying blood flow (i.e., velocity and image intensity) through a microfluidic device, in which an air-compressed syringe (ACS) is used to control the sample injection. The microfluidic device used is composed of two channels (pressure channel (PC), and blood channel (BC)), an inlet, and an outlet. A single ACS (i.e., air suction = 0.4 mL, blood suction = 0.4 mL, and air compression = 0.3 mL) is employed to supply blood into the microfluidic channel. At an initial time (t < 10 s), the pressure index (PI) is evaluated by analyzing the intensity of microscopy images of blood samples collected inside PC. During blood delivery with ACS, shear rates of blood flows vary continuously over time. After a certain amount of time has elapsed (t > 30 s), two RBC aggregation indices (i.e., S_EAI: without information on shear rate, and erythrocyte aggregation index (EAI): with information on shear rate) are quantified by analyzing the image intensity and velocity field of blood flow in BC. According to experimental results, PI depends significantly on the characteristics of the blood samples (i.e., hematocrit or base solutions) and can be used effectively as an alternative to blood viscosity. In addition, S_EAI and EAI also depend significantly on the degree of RBC aggregation. In conclusion, on the basis of three indices (two RBC aggregation indices and pressure index), the proposed method is capable of measuring RBCs aggregation consistently using a microfluidic device.

In vitro and ex vivo measurement of the biophysical properties of blood using microfluidic platforms and animal models

Haemorheologically impaired microcirculation, such as blood clotting or abnormal blood flow, causes interrupted blood flows in vascular networks. The biophysical properties of blood, including blood viscosity, blood viscoelasticity, haematocrit, red blood bell (RBC) aggregation, erythrocyte sedimentation rate and RBC deformability, have been used to monitor haematological diseases. In this review, we summarise several techniques for measuring haemorheological properties, such as blood viscosity, RBC deformability and RBC aggregation, using in vitro microfluidic platforms. Several methodologies for the measurement of haemorheological properties with the assistance of an extracorporeal rat bypass loop are also presented. We briefly discuss several emerging technologies for continuous, long-term, multiple measurements of haemorheological properties under in vitro or ex vivo conditions.

3D printed microfluidic viscometer based on the co-flowing stream

Considering the role of viscosity in the dynamics of physical, chemical, and biological systems, accurate measurement of viscosity is essential. Although many conventional viscometers have been widely used, these conventional viscometers suffer from some drawbacks. In this study, a three-dimensional (3D) printed microfluidic viscometer was proposed based on the estimation of the pressure between two fluids to easily measure viscosity with small samples. The 3D printed microfluidic viscometer can be fabricated through amine-epoxy bonding on 3D printed blocks. By separately delivering samples and reference fluids into two inlets, an interfacial line could be induced. Based on the relation between the pressure ratio and the width of the reference flow, the viscosity (μ) of the sample can be estimated by measuring the relative width of the reference flow. The relation between the pressure and interfacial width between test samples and reference flows in the 3D printed microfluidic viscometers was analyzed by experiment and simulation to determine the effects of the mesh-like pattern of the 3D printed viscometers on the pressure estimation. To validate the proposed method, the viscosity values of glycerol mixtures measured by the 3D printed viscometer were compared with those measured by a conventional viscometer. As an application of the 3D printed viscometer, the viscosity curves for blood samples collected from diabetic and non-diabetic patients depending on their shear rates were compared. As expected, a high blood viscosity in the diabetic group was observed. Based on the experimental demonstrations, the 3D printed viscometer has strong potential to develop portable viscometers that can be translated to commercial outcomes.

STREPTOZOTOCIN-INDUCED DIABETES MELLITUS - A PARADOX OF HIGH INTRINSIC PLATELET REACTIVITY AND LOW IN VITRO PLATELET AGGREGATION

CONTEXT

Studies of platelet function in diabetics are inconsistent, some studies reporting higher platelet reactivity, while others showed no change.

OBJECTIVE

We aimed to evaluate platelet indices and in vitro platelet aggregation in rats with long-lasting (28 weeks) diabetes mellitus.

DESIGN

Twelve controls and 14 diabetic rats were investigated. Diabetes was induced in 11-week-old rats using streptozotocin (60 mg/kg,i.p.). Platelet indices and in vitro adenosine diphosphate (ADP)-, protease-activated receptor 4 (PAR4) agonist-, and arachidonic acid (AA)-induced platelet aggregation were assessed at the age of 38 weeks.

RESULTS

Compared to controls, diabetic rats presented lower platelet count and plateletcrit (both p≤0.001), and higher mean platelet volume (p<0.01). ADP- (p=0.04) and AA-induced (p<0.01) platelet aggregation were lower in diabetic compared with control rats, whereas PAR4 agonist-induced platelet aggregation was similar between the two groups (p=1.00).

CONCLUSIONS

This study demonstrates a paradox of high intrinsic platelet reactivity and low in vitro ADP- and AA-induced platelet aggregation in diabetic rats compared with non-diabetic controls. The relevance of in vitro platelet aggregation to the contribution of platelets to in vivo thromboembolic events in diabetic rats remains questionable.

Quantifying Platelet Margination in Diabetic Blood Flow

Patients with type 2 diabetes mellitus (T2DM) develop thrombotic abnormalities strongly associated with cardiovascular diseases. In addition to the changes of numerous coagulation factors such as elevated levels of thrombin and fibrinogen, the abnormal rheological effects of red blood cells (RBCs) and platelets flowing in blood are crucial in platelet adhesion and thrombus formation in T2DM. An important process contributing to the latter is the platelet margination. We employ the dissipative particle dynamics method to seamlessly model cells, plasma, and vessel walls. We perform a systematic study on RBC and platelet transport in cylindrical vessels by considering different cell shapes, sizes, and RBC deformabilities in healthy and T2DM blood, as well as variable flowrates and hematocrit. In particular, we use cellular-level RBC and platelet models with parameters derived from patient-specific data and present a sensitivity study. We find T2DM RBCs, which are less deformable compared to normal RBCs, lower the transport of platelets toward the vessel walls, whereas platelets with higher mean volume (often observed in T2DM) lead to enhanced margination. Furthermore, increasing the flowrate or hematocrit enhances platelet margination. We also investigated the effect of platelet shape and observed a nonmonotonic variation with the highest near-wall concentration corresponding to platelets with a moderate aspect ratio of 0.38. We examine the role of white blood cells (WBCs), whose count is increased notably in T2DM patients. We find that WBC rolling or WBC adhesion tends to decrease platelet margination due to hydrodynamic effects. To the best of our knowledge, such simulations of blood including all blood cells have not been performed before, and our quantitative findings can help separate the effects of hydrodynamic interactions from adhesive interactions and potentially shed light on the associated pathological processes in T2DM such as increased inflammatory response, platelet activation and adhesion, and ultimately thrombus formation.

Synergistic Integration of Laboratory and Numerical Approaches in Studies of the Biomechanics of Diseased Red Blood Cells

In red blood cell (RBC) disorders, such as sickle cell disease, hereditary spherocytosis, and diabetes, alterations to the size and shape of RBCs due to either mutations of RBC proteins or changes to the extracellular environment, lead to compromised cell deformability, impaired cell stability, and increased propensity to aggregate. Numerous laboratory approaches have been implemented to elucidate the pathogenesis of RBC disorders. Concurrently, computational RBC models have been developed to simulate the dynamics of RBCs under physiological and pathological conditions. In this work, we review recent laboratory and computational studies of disordered RBCs. Distinguished from previous reviews, we emphasize how experimental techniques and computational modeling can be synergically integrated to improve the understanding of the pathophysiology of hematological disorders.

Mechanism of retinal pericyte migration through Angiopoietin/Tie-2 signaling pathway on diabetic rats

AIM

To investigate the mechanism of pericyte migration through Angiopoietin-2 (Ang-2)/Tie-2 signaling pathway.

METHODS

We divided the rats into 5 groups. Each diabetic rat model groups injected with Tie-2 inhibitor, ERK1/2 inhibitor, Akt/PKB inhibitor, and DMSO intravitreal. Retinal digest preparation was done to examine the retinal vasculature including pericyte: endothelial ratio, and morphology of pericyte migration. Tie-2, ERK1/2 and Akt/PKB phosporylation were analyzed by confocal laser scanning microscopy.

RESULTS

There was a correlation between pericyte migration with increasing Ang-2 (P<0.05). Pericyte number reduced by 40% (1:2.4) after 5wk diabetes on diabetic rats. The pericyte: endothelial ratio on group with Tie-2 inhibitor were 1:1.8. The same result shows on group with Akt/PKB inhibition. ERK1/2 inhibitor group shows the best results of pericyte: endothelial ratio (1:1.7). Inhibition on Tie-2 receptor decreased the phosphorylation activity of Tie-2, ERK1/2 and Akt/PKB pathway. ERK1/2 inhibition also decreasing the phosphorylation of Tie-2 and Akt/PKB. But on Akt/PKB inhibition, the phosphorylation of Tie-2 and ERK1/2 were relative the same.

CONCLUSION

Ang-2 has a role for pericyte migration on diabetic rats through Tie-2 receptor, ERK1/2 and Akt/PKB pathways. ERK1/2 is a dominant pathway based on the ability to supress another pathway activity and decreasing pericyte migration on diabetic rats.

Effects of kisspeptin on diabetic rat platelets

Hyperglycemia, hyperlipidemia, and free radicals result in platelet activation and atherogenesis. Kisspeptin (KP) is able to regulate metabolism, hemostasis, and the development of atherosclerosis. We examined whether platelet aggregation of streptozotocin-induced diabetic rats depends on the inducer type and if KP-13 and RF-9 (a kisspeptin receptor modifier) can influence platelet function. We measured the speed and the maximum of aggregation, along with the area under the curve. Serum glucose and calcium levels and urine formation of diabetic animals increased, while the body mass and platelet count decreased. Collagen was the most effective inducer of platelet aggregation. The aggregability of nondiabetic platelets was elevated in the presence of 5 × 10−8 mol/L KP-13. This effect was less expressed in diabetic animals. The effectivity of RF-9 was stronger than that of KP-13 in nondiabetic platelets, however it was ineffective in diabetic animals. RF-9 pre-treatment did not change the effects of 5 × 10−8 mol/L KP-13 in either animal group. The in vivo activation of diabetic platelets, which may be due to elevated serum calcium, induces thrombocytopenia and may lead to reduced in vitro aggregability. We could not demonstrate the antagonistic effect of RF-9 against KP-13 in isolated platelets.

Enhanced adhesion of blood platelets to intact endothelium of mesenteric vascular bed in mice with streptozotocin-induced diabetes is mediated by an up-regulated endothelial surface deposition of VWF - In vivo study

Numerous in vitro experiments have confirmed that a dysfunctional endothelium is characterized by, inter alia, a higher affinity for binding of platelets and leukocytes. However, there is still no direct evidence for greater interaction between platelets and intact endothelium in in vivo animal models of diabetes. Therefore, the present study examines the pro-adhesive properties of endothelium change in vivo as an effect of streptozotocin (STZ)-induced diabetes and the role of two key platelet receptors: GPIb-IX-V and GPIIb/IIIa. Mice of C57BL strain with streptozotocin-induced diabetes were used in the study. Flow cytometry was used to assess basal activation and reactivity of platelets. Adhesion of platelets to the vascular wall was visualized with the use of intravital microscopy in mesentery. The contribution of GPIIb/IIIa and GPIb-IX-V was evaluated by the injection of Fab fragments of respective antibodies. The integrity of the endothelium and vWf expression were evaluated histochemically. Basal activation and reactivity of platelets in streptozotocin-diabetic mice were elevated. Blood platelets adhered more often to the vascular wall of diabetic mice than nondiabetic animals: 11.9 (6.4; 32.8) plt/min/mm² (median [IQR]) vs 2.7 (1.3; 6.4) plt/min/mm². The injection of anti-GPIbα antibodies decreased the number of adhering platelets from 89.5 (34.0; 113.1) plt/min/mm² (median [IQR]) in mice treated with isotype antibodies to 3.1 (1.7; 5.6) plt/min/mm² in mice treated with blocking antibodies. The effect of GPIIb/IIIa blockage was not significant. Immunohistochemistry revealed a higher expression of vWF in the endothelium of STZ mice, but no substantial changes in endothelial morphology were detected. To conclude, the study shows that the platelets interact more frequently with the mesenteric vascular bed in mice with 1-month STZ-induced diabetes than in healthy mice. These interactions are mediated via platelet GPIb-IX-V and are driven by increased expression of vWF in endothelial cells.

Microfluidic system for monitoring temporal variations of hemorheological properties and platelet adhesion in LPS-injected rats

Sepsis causes multiple organs failures and eventually death. Changes in blood constituents due to sepsis lead to alterations in hemorheological properties, and cell adhesiveness. In this study, a new microfluidic system is proposed to measure temporal variations in biophysical properties of blood after injecting lipopolysaccharide (LPS) into a rat extracorporeal model under ex vivo condition. To measure blood viscosity, the interfacial line between blood and a reference fluid is formed in a Y-shaped channel. Based on the relation between interfacial width and pressure ratio, the temporal variation in blood viscosity is estimated. Optical images of blood flows are analyzed by decreasing flow rate for examination of red blood cell (RBC) aggregation. Platelets initiated by shear acceleration around the stenosis adhere to the post-stenosed region. By applying a correlation map that visualizes the decorrelation of the streaming blood flow, the area of adhered platelets can be quantitatively attained without labeling of platelets. To assess sepsis inflammation, conventional biomarkers (PCT and IL-8) are also monitored. The increasing tendency for blood viscosity, RBC aggregation, platelet adhesion, and septic biomarkers are observed after LPS injection. This microfluidic system would be beneficial for monitoring the changes in hemorheological properties and platelet activation caused by sepsis.

Blood oxidative stress (BLOS) is a secondary host defense system responding normally to anaerobic wound infection and inadvertently to dietary ultra-exogenous sulfide formation (USF)

Blood oxidative stress (BLOS) is the presence of white blood cells and platelets that are generating high levels of reactive oxygen species (ROS). A mathematical model links the level of BLOS or BLOS# and plasma sulfide concentration. An increase in the BLOS# reduces the plasma sulfide concentration. The reported maximum plasma sulfide concentration for defined health conditions were used to calculate the minimum BLOS#. Elevated BLOS generates high plasma concentration of ROS, which triggers multiple responses in the body that protect the host. First, insulin production by the pancreas is inhibited, which results in elevated blood glucose levels. This results in advanced glycation end products (AGE), which thicken the blood vessel wall. Elevated blood glucose levels also increases urination, which reduces the availability of substrates for infectious bacteria. Second, one or more signaling molecules are stimulated to produce vascular hypertrophy resulting in hypertension. Third, the initial stage of atherosclerosis thickens the blood vessel wall while also protecting the inner surface of the blood vessels from localized infection. The first three mechanisms provide added protection against pathogen migration through the blood vessel wall and reduce the cross-sectional area of blood vessels, which increases the retention time (RT) for improved ROS inactivation of pathogens. Fourth, genes expressed in the liver, which are associated with drug oxidation and uptake transport, are inhibited. This inhibition protects the host from any toxins produced by an anaerobic infection. Elevated BLOS also reduces plasma sulfide concentration, which inhibits wound healing and extends aerobic conditions of the wound. The normal induction of BLOS offers a short-term, cascade of several primary mechanisms for secondary defense against anaerobic infection of a wound. Normal induction of BLOS is due to ultra-exogenous sulfide formation (USF) generated by a local anaerobic infection of a wound in the natural environment. The presence of BLOS without infection is indicative of inadvertent dietary induction. Long-term dietary BLOS results in many severe inflammatory diseases and cancers that are common in an ageing population. Glands were identified as more susceptible to cancers caused by long-term dietary BLOS. Variable BLOS levels in patients of clinical trials may also be reducing effectiveness of experimental drugs and causing drug toxicity. If BLOS is confirmed as a secondary defense against infection that is inadvertently triggered by diet, then a large number of common health problems may be treated and managed by apheresis and dietary changes.