Vitamin E in young and old human red blood cells

Antioxidant Supplementation Protects Elite Athlete Muscle Integrity During Submaximal Training

PURPOSE

To determine (1) the effect of a 40-minute steady-state run on muscle membrane integrity of elite athletes as reflected by serum creatine kinase (CK), (2) whether antioxidant supplementation (AS) with vitamins E and C has a protective effect, and (3) if a minimal blood concentration of vitamin E or C is required for any such protection.

METHODS

Fifteen elite-level endurance athletes (V˙O2max=71.5±1.2 mL·kg-1 min-1) were randomly assigned to 6 weeks AS (1000 IU·d-1 natural vitamin E and 1000 mg·d-1 vitamin C) or placebo. Using a double-blind crossover design and 4-week washout period, each treatment was followed by a 40-minute steady-state run at 3 mM blood lactate. Blood samples before and 0 and 24 hours after the run were assayed for serum and red cell α-tocopherol (α-TOH), serum ascorbate, and CK.

RESULTS

The AS produced a 2.5-fold, well-correlated (r = .84) increase in serum and red cell α-TOH (P < .001) that attenuated the increase in postrun CK (P = .01). There was no change in serum ascorbate with AS and no relationship with CK (P > .1). Curvilinear regression revealed some evidence that a critical level of serum α-TOH in the vicinity of 12 mg·L-1 was required to attenuate CK efflux, a level only achieved with AS.

CONCLUSION

The muscle membrane integrity of elite-level athletes is compromised even during steady-state running of moderate intensity and duration. The AS provided a protective effect, with evidence that a serum α-TOH concentration of around 12 mg·L-1 is required.

The Role of Haptoglobin Polymorphism in Cardiovascular Disease in the Setting of Diabetes

Atherosclerotic cardiovascular disease (CVD) is the major cause of morbidity and mortality in individuals with diabetes mellitus (DM). Preclinical models have suggested that excessive oxidative stress and hyperglycemia are directly responsible for this pathological association. However, numerous clinical trials involving the administration of high doses of the antioxidant vitamin E or attempts at strict glycemic control have failed to show a significant reduction of CVD in DM patients. We describe here a possible explanation for the failure of these trials, that being their lack of proper patient selection. The haptoglobin (Hp) genotype is a major determinant of the risk of CVD in the setting of DM. Treatment of individuals with the high-risk Hp genotype with antioxidants or aggressive glycemic control has shown benefit in several small studies. These studies suggest a precision medicine-based approach to preventing diabetes complications. This approach would have a profound effect on the costs of diabetes care and could dramatically reduce morbidity from diabetes.

Meta-analysis of the association of the haptoglobin genotype with cardiovascular outcomes and the pharmacogenomic interactions with vitamin E supplementation

Objectives

The objectives of the study were to compile and summarize the data from all of the clinical trials designed to examine the association between haptoglobin (Hp) genotype and incidence of cardiovascular (CV) events in patients with diabetes mellitus (DM) and to assess the impact of vitamin E treatment on CV outcomes according to the Hp genotype.

Background

The Hp genotype could serve as a predictive biomarker to DM patients who may benefit from vitamin E therapy.

Methods

The electronic databases MEDLINE, PubMed, EMBASE and the Cochrane Library for Central Register of Clinical Trials were searched systematically using the following MESH terms: "haptoglobin genotype", "diabetes mellitus" and "cardiovascular events".

Results

Overall, 13 studies fit the inclusion criteria for this analysis, yielding a large study population that included 6,161 patients without Hp 2-2 and 4,684 patients with Hp 2-2. The analysis of these studies showed that the incidence of CV events in DM patients with the Hp 2-2 genotype was significantly increased as compared to non-Hp 2-2 patients in all three subgroups of case-control (OR: 2.2, 95% CI: 1.3-3.6; P=0.003), cohort (OR: 1.3, 95% CI: 1.2-1.5; P=0.001) and randomized controlled trials (OR: 1.6, 1.2-2.2; P=0.005). Among patients with the Hp 2-2 genotype, administration of vitamin E was associated with lower rates of CV events (OR: 0.66, 95% CI: 0.45-0.95; P=0.025). Further investigation into the association between Hp 2-2 and myocardial infarction, stroke, mortality and end-stage renal disease was also performed.

Conclusion

The Hp genotype is a risk factor for CV events in patients with DM, and administration of vitamin E appears to offer a low cost and accessible means of reducing CV events and mortality in this population.

Interaction Between the Haptoglobin Genotype and Vitamin E on Cardiovascular Disease in Diabetes

PURPOSE OF REVIEW

Despite compelling evidence regarding the importance of oxidant stress in the development of vascular complications and observational studies suggesting that vitamin E may be protective from these complications, multiple clinical trials have failed to show benefit from vitamin E supplementation in the prevention of vascular complications in diabetes. One possible explanation for this failure of vitamin E may have been inappropriate patient selection. This review seeks to provide the clinical evidence and mechanistic basis for why a subset of individuals defined by their haptoglobin (Hp) genotype may derive cardiovascular protection by vitamin E supplementation.

RECENT FINDINGS

Clinical trial data from the HOPE, ICARE, and WHS studies is presented showing a pharmacogenomic interaction between the Hp genotype and vitamin E on the development of CVD. Specifically, in individuals with diabetes and the Hp2-2 genotype, vitamin E has been shown to be associated with an approximately 35% reduction in CVD. Cardioprotection by vitamin E in individuals with the Hp2-2 genotype appears to be mediated in part by an improvement in HDL functionality as demonstrated in three independent trials in both type 1 diabetes and type 2 diabetes. Vitamin E may provide benefit in reducing CVD in Hp2-2 individuals with diabetes. However, in order for this pharmacogenomic algorithm to be accepted as a standard of care and used clinically, an additional large prospective study will need to be performed.

Excitotoxins, Mitochondrial and Redox Disturbances in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). There is increasing evidence that MS is not only characterized by immune mediated inflammatory reactions, but also by neurodegenerative processes. There is cumulating evidence that neurodegenerative processes, for example mitochondrial dysfunction, oxidative stress, and glutamate (Glu) excitotoxicity, seem to play an important role in the pathogenesis of MS. The alteration of mitochondrial homeostasis leads to the formation of excitotoxins and redox disturbances. Mitochondrial dysfunction (energy disposal failure, apoptosis, etc.), redox disturbances (oxidative stress and enhanced reactive oxygen and nitrogen species production), and excitotoxicity (Glu mediated toxicity) may play an important role in the progression of the disease, causing axonal and neuronal damage. This review focuses on the mechanisms of mitochondrial dysfunction (including mitochondrial DNA (mtDNA) defects and mitochondrial structural/functional changes), oxidative stress (including reactive oxygen and nitric species), and excitotoxicity that are involved in MS and also discusses the potential targets and tools for therapeutic approaches in the future.

Focus on Pivotal Role of Dietary Intake (Diet and Supplement) and Blood Levels of Tocopherols and Tocotrienols in Obtaining Successful Aging

Numerous specific age-related morbidities have been correlated with low intake and serum levels of tocopherols and tocotrienols. We performed a review in order to evaluate the extant evidence regarding: (1) the association between intake and serum levels of tocopherols and tocotrienols and age-related pathologies (osteoporosis, sarcopenia and cognitive impairment); and (2) the optimum diet therapy or supplementation with tocopherols and tocotrienols for the treatment of these abnormalities. This review included 51 eligible studies. The recent literature underlines that, given the detrimental effect of low intake and serum levels of tocopherols and tocotrienols on bone, muscle mass, and cognitive function, a change in the lifestyle must be the cornerstone in the prevention of these specific age-related pathologies related to vitamin E-deficient status. The optimum diet therapy in the elderly for avoiding vitamin E deficiency and its negative correlates, such as high inflammation and oxidation, must aim at achieving specific nutritional goals. These goals must be reached through: accession of the elderly subjects to specific personalized dietary programs aimed at achieving and/or maintaining body weight (avoid malnutrition); increase their intake of food rich in vitamin E, such as derivatives of oily seeds (in particular wheat germ oil), olive oil, hazelnuts, walnuts, almonds, and cereals rich in vitamin E (such as specific rice cultivar rich in tocotrienols) or take vitamin E supplements. In this case, vitamin E can be correctly used in a personalized way either for the outcome from the pathology or to achieve healthy aging and longevity without any adverse effects.

Tyrosol, a phenolic compound, ameliorates hyperglycemia by regulating key enzymes of carbohydrate metabolism in streptozotocin induced diabetic rats

The present study was designed to evaluate the effects of tyrosol, a phenolic compound, on the activities of key enzymes of carbohydrate metabolism in the control and streptozotocin-induced diabetic rats. Diabetes mellitus was induced in rats by a single intraperitoneal injection of streptozotocin (40 mg/kg body weight). Experimental rats were administered tyrosol 1 ml intra gastrically at the doses of 5, 10 and 20mg/kg body weight and glibenclamide 1 ml at a dose of 600 μg/kg body weight once a day for 45 days. At the end of the experimental period, diabetic control rats exhibited significant (p<0.05) increase in plasma glucose, glycosylated hemoglobin with significant (p<0.05) decrease in plasma insulin, total hemoglobin and body weight. The activities of key enzymes of carbohydrate metabolism such as phosphoenolpyruvate carboxykinase, fructose-1,6-bisphosphatase and glucose-6-phosphatase were significantly (p<0.05) increased and the activities of hexokinase and glucose-6-phosphate dehydrogenase were significantly (p<0.05) decreased in the liver and kidney of diabetic control rats. Further, antioxidants were lowered in diabetic control rats. A significant (p<0.05) decline in glycogen level in the liver and muscle and glycogen synthase activity in the liver and a significant (p<0.05) increase in the activity of liver glycogen phosphorylase were observed in diabetic control rats compared to normal control rats. Oral administration of tyrosol to diabetic rats reversed all the above mentioned biochemical parameters to near normal in a dose dependent manner. Tyrosol at a dose of 20mg/kg body weight showed the highest significant effect than the other two doses. Immunohistochemical staining of pancreas revealed that tyrosol treated diabetic rats showed increased insulin immunoreactive β-cells, which confirmed the biochemical findings. The observed results were compared with glibenclamide, a standard oral hypoglycemic drug. The results of the present study suggest that tyrosol decreases hyperglycemia, by its antioxidant effect.

Effects of N-adamantyl-4-methylthiazol-2-amine on hyperglycemia, hyperlipidemia and oxidative stress in streptozotocin-induced diabetic rats

Thiazole derivatives are attractive candidates for drug development because they can be efficiently synthesized and are active against a number of diseases and conditions, including diabetes. In our present study, we investigated the anti-inflammatory and antioxidant properties of N-adamantyl-4-methylthiazol-2-amine (KHG26693), a new thiazole derivative, in a streptozotocin (STZ)-induced model of diabetes mellitus. STZ-induced diabetic rats were intraperitoneally administered KHG26693 (3mg/kg-body weight/day) for 4 weeks. KHG26693 administration significantly decreased blood glucose, triglycerides, and cholesterol and increased insulin. KHG26693 also suppressed several inflammatory responses in STZ-induced diabetic rats, as evidenced by decreased levels of serum tumor necrosis factor-α, interleukin-1β, and nitric oxide. Additionally, KHG26693 significantly modulated hepatic lipid peroxidation, catalase and superoxide dismutase activity, and the nonenzymatic antioxidant status (e.g., vitamins C and E), and reduced the glutathione content. These anti-inflammatory/antioxidative actions occurred as a result of the downregulation of inducible nitric oxide synthase and nuclear factor-kappa B. Taken together, our results suggest that KHG26693 successfully reduces the production of oxidative stress in STZ-induced diabetic rats by regulating the oxidation-reduction system, specifically increasing antioxidant capacity. Furthermore, KHG26693 treatment significantly reverted the key enzymes of glucose metabolism, such as glucokinase, glucose-6-phosphatase, glycogen synthase, glycogen phosphorylase, and fructose-1,6-bisphosphatase, to near-normal levels in liver tissues. These results indicate that KHG26693 normalizes disturbed glucose metabolism by enhancing glucose utilization and decreasing liver glucose production via insulin release, suggesting the possibility of future diabetes treatments.

Mangiferin from Salacia chinensis prevents oxidative stress and protects pancreatic β-cells in streptozotocin-induced diabetic rats

Oxidative stress in diabetic tissues is a consequence of free radical accumulation with concurrently impaired natural antioxidants status and results in oxidative tissue damage. The present study investigated the protective effects of mangiferin against pancreatic β-cell damage and on the antioxidant defense systems in streptozotocin (STZ)-induced diabetic rats. Diabetes was experimentally induced by a single intraperitoneal injection of STZ. Oxidative stress biomarkers such as tissue malondialdehyde, hydroperoxides, reduced glutathione (GSH) content, and nonenzymatic antioxidants were measured. Biochemical observations were further substantiated with histological examination and ultrastructural studies in the pancreas of diabetic, glibenclamide and mangiferin-treated diabetic rats (dosage of 40 mg/kg body weight daily for 30 days). Oral administration of mangiferin and glibenclamide to diabetic rats significantly decreased the level of blood glucose and increased levels of insulin. Additionally, mangiferin treatment significantly modulated the pancreatic nonenzymatic antioxidants status (vitamin C, vitamin E, ceruloplasmin, and reduced GSH content) and other oxidative stress biomarkers. The histoarchitecture of diabetic rats showed degenerated pancreas with lower β-cell counts, but mangiferin treatment effectively regenerated insulin secreting islet cells. The electron microscopic study revealed damaged nuclear envelope and mitochondria and fewer secretory granules in pancreas of diabetic rats; however, mangiferin treatment nearly normalized pancreatic architecture. The present findings suggest that mangiferin treatment exerts a therapeutic protective nature in diabetes by decreasing oxidative stress and protecting against pancreatic β-cell damage, which may be attributable to its antioxidative properties.

Vitamin E-gene interactions in aging and inflammatory age-related diseases: implications for treatment. A systematic review

Aging is a complex biological phenomenon in which the deficiency of the nutritional state combined with the presence of chronic inflammation and oxidative stress contribute to the development of many age-related diseases. Under this profile, the free radicals produced by the oxidative stress lead to a damage of DNA, lipids and proteins with subsequent altered cellular homeostasis and integrity. In young-adult age, the cell has a complex efficient system to maintain a proper balance between the levels of free radicals and antioxidants ensuring the integrity of cellular components. In contrast, in old age this balance is poorly efficient compromising cellular homeostasis. Supplementation with Vitamin E can restore the balance and protect against the deteriorating effects of oxidative stress, progression of degenerative diseases, and aging. Experiments in cell cultures and in animals have clearly shown that Vitamin E has a pivotal role as antioxidant agent against the lipid peroxidation on cell membranes preserving the tissue cells from the oxidative damage. Such a role has been well documented in immune, endothelial, and brain cells from old animals describing how the Vitamin E works both at cytoplasmatic and nuclear levels with an influence on many genes related to the inflammatory/immune response. All these findings have supported a lot of clinical trials in old humans and in inflammatory age-related diseases with however contradictory and inconsistent results and even indicating a dangerous role of Vitamin E able to affect mortality. Various factors can contribute to all the discrepancies. Among them, the doses and the various isoforms of Vitamin E family (α,β,γ,δ tocopherols and the corresponding tocotrienols) used in different trials. However, the more plausible gap is the poor consideration of the Vitamin E-gene interactions that may open new roadmaps for a correct and personalized Vitamin E supplementation in aging and age-related diseases with satisfactory results in order to reach healthy aging and longevity. In this review, this peculiar nutrigenomic and/or nutrigenetic aspect is reported and discussed at the light of specific polymorphisms affecting the Vitamin E bioactivity.

Antioxidant supplementation ameliorates molecular deficits in Smith-Lemli-Opitz syndrome

BACKGROUND

Smith-Lemli-Opitz syndrome (SLOS) is an inborn error of cholesterol biosynthesis characterized by diminished cholesterol and increased 7-dehydrocholesterol (7-DHC) levels. 7-Dehydrocholesterol is highly reactive, giving rise to biologically active oxysterols.

METHODS

7-DHC-derived oxysterols were measured in fibroblasts from SLOS patients and an in vivo SLOS rodent model using high-performance liquid chromatography tandem mass spectrometry. Expression of lipid biosynthesis genes was ascertained by quantitative polymerase chain reaction and Western blot. The effects of an antioxidant mixture of vitamin A, coenzyme Q10, vitamin C, and vitamin E were evaluated for their potential to reduce formation of 7-DHC oxysterols in fibroblast from SLOS patients. Finally, the effect of maternal feeding of vitamin E enriched diet was ascertained in the brain and liver of newborn SLOS mice.

RESULTS

In cultured human SLOS fibroblasts, the antioxidant mixture led to decreased levels of the 7-DHC-derived oxysterol, 3β,5α-dihydroxycholest-7-en-6-one. Furthermore, gene expression changes in SLOS human fibroblasts were normalized with antioxidant treatment. The active ingredient appeared to be vitamin E, as even at low concentrations, it significantly decreased 3β,5α-dihydroxycholest-7-en-6-one levels. In addition, analyzing a mouse SLOS model revealed that feeding a vitamin E enriched diet to pregnant female mice led to a decrease in oxysterol formation in brain and liver tissues of the newborn Dhcr7-knockout pups.

CONCLUSIONS

Considering the adverse effects of 7-DHC-derived oxysterols in neuronal and glial cultures and the positive effects of antioxidants in patient cell cultures and the transgenic mouse model, we believe that preventing formation of 7-DHC oxysterols is critical for countering the detrimental effects of DHCR7 mutations.

Antihyperglycemic and antioxidant effects of a flavanone, naringenin, in streptozotocin-nicotinamide-induced experimental diabetic rats

In the present study, the putative antihyperglycemic and antioxidant effects of a flavanone, naringenin, were evaluated in comparison with those of glyclazide, a standard drug for therapy of diabetes mellitus. Diabetes was induced experimentally in 12-h-fasted rats by intraperitoneal injections of first streptozotocin (50 mg/kg b.w.) and then of nicotinamide (110 mg/kg b.w.) after a 15-min interval. Untreated diabetic rats revealed the following in comparison with normal rats: significantly higher mean levels of blood glucose and glycosylated hemoglobin, significantly lower mean levels of serum insulin, significantly lower mean activities of pancreatic antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase), significantly lower mean levels of plasma non-enzymatic antioxidants (reduced glutathione, vitamin C , vitamin E), significantly elevated mean levels of pancreatic malondialdehyde (MDA) and significantly elevated mean activities of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH). Following oral administration of naringenin (50 mg/kg b.w./day) to diabetic rats for 21 days, the following observations were made in comparison with untreated diabetic rats: significantly lower mean levels of fasting blood glucose and glycosylated hemoglobin, significantly elevated serum insulin levels, significantly higher mean activities of pancreatic enzymatic antioxidants, significantly higher mean levels of plasma non-enzymatic antioxidants, lower mean pancreatic tissue levels of MDA and lower mean activities of ALT, AST, ALP and LDH in serum. The values obtained in the naringenin-treated animals approximated those observed in glyclazide-treated animals. Histopathological studies appeared to suggest a protective effect of naringenin on the pancreatic tissue in diabetic rats. These results suggest that naringenin exhibits antihyperglycemic and antioxidant effects in experimental diabetic rats.

Characterization of tocopherol cyclases from higher plants and cyanobacteria. Evolutionary implications for tocopherol synthesis and function

Tocopherols are lipophilic antioxidants synthesized exclusively by photosynthetic organisms and collectively constitute vitamin E, an essential nutrient for both humans and animals. Tocopherol cyclase (TC) catalyzes the conversion of various phytyl quinol pathway intermediates to their corresponding tocopherols through the formation of the chromanol ring. Herein, the molecular and biochemical characterization of TCs from Arabidopsis (VTE1 [VITAMIN E 1]), Zea mays (SXD1 [Sucrose Export Deficient 1]) and Synechocystis sp. PCC6803 (slr1737) are described. Mutations in the VTE1, SXD1, or slr1737 genes resulted in both tocopherol deficiency and the accumulation of 2,3-dimethyl-6-phytyl-1,4-benzoquinone (DMPBQ), a TC substrate. Recombinant SXD1 and VTE1 proteins are able to convert DMPBQ to gamma-tocopherol in vitro. In addition, expression of maize SXD1 in a Synechocystis sp. PCC6803 slr1737 knockout mutant restored tocopherol synthesis, indicating that TC activity is evolutionarily conserved between plants and cyanobacteria. Sequence analysis identified a highly conserved 30-amino acid C-terminal domain in plant TCs that is absent from cyanobacterial orthologs. vte1-2 causes a truncation within this C-terminal domain, and the resulting mutant phenotype suggests that this domain is necessary for TC activity in plants. The defective export of Suc in sxd1 suggests that in addition to presumed antioxidant activities, tocopherols or tocopherol breakdown products also function as signal transduction molecules, or, alternatively, the DMPBQ that accumulates in sxd1 disrupts signaling required for efficient Suc export in maize.

Antithrombotic effect of PMC, a potent alpha-tocopherol analogue on platelet plug formation in vivo

Platelet thrombi formation was induced by irradiation of mesenteric venules with filtered light in mice pretreated intravenously with fluorescein sodium. PMC (2, 2, 5, 7, 8-pentamethyl-6-hydroxychromane; 20 microg/g, i.v.) significantly prolonged the latent period of inducing platelet plug formation in mesenteric venules. When fluorescein sodium was given at 10 microg/kg, PMC (20 microg/g) delayed occlusion time by about 1.7-fold. Furthermore, aspirin (250 microg/g) also showed similar activity in delaying the occlusion time. On a molar basis, PMC was about 14-fold more potent than aspirin at delaying the occlusion time. PMC was also effective in reducing the mortality of ADP-induced acute pulmonary thromboembolism in mice when administered intravenously at doses of 5 and 10 microg/g. In addition, intravenous injection of PMC (5 microg/g) significantly prolonged bleeding time by about 1.6-fold compared with normal saline in severed mesenteric arteries of rats. Continuous infusion of PMC (1 microg/g/min) significantly increased the bleeding time by about 1.6-fold and the bleeding time was also significantly prolonged for up to 90 min after cessation of PMC infusion. These results suggest that PMC has an effective antiplatelet effect in vivo and may be a potential therapeutic agent for arterial thrombosis, but must be assessed further for toxicity.

Diminished blood levels of reduced glutathione and alpha-tocopherol in two triosephosphate isomerase-deficient brothers

The glutathione redox system and alpha-tocopherol, both of which are essential for maintaining the normal structure of biological membranes, some other lipid-soluble antioxidants (lycopene, beta-carotene, retinol), and lipid peroxidation, were investigated in the blood from two triosephosphate isomerase (TPI)-deficient brothers. Both of the genetically identical compound heterozygote brothers have congenital hemolytic anemia, but only one of them has a neurological defect, the second cardinal symptom of TPI deficiency. Whole blood reduced glutathione levels were markedly decreased in both brothers. The glutathione reductase activities as well as the NADPH contents of their erythrocytes were in the normal range or slightly enhanced. Increased ratio of oxidized/reduced glutathione, elevated glutathione S-transferase activity, and increased d-lactate level, a metabolite of the glyoxalase pathway, were detected only in the neurologically affected propositus. The plasma carotenoids (lycopene + beta-carotene), alpha-tocopherol/cholesterol + triglyceride ratios, and the erythrocyte alpha-tocopherol levels were significantly decreased in both patients. It seems conceivable that membrane alterations due to the low level of these reducing agents may contribute to the shortened life span of erythrocytes. The imbalance of the prooxidant/antioxidant homeostasis as well as the increased rate of methylglyoxal formation may also have been involved in the development of the neurological manifestations in the propositus.

The antiplatelet activity of PMC, a potent alpha-tocopherol analogue, is mediated through inhibition of cyclo-oxygenase

PMC, a potent alpha-tocopherol derivative, dose-dependently (5-25 microM) inhibited the ATP-release reaction and platelet aggregation in washed human platelets stimulated by agonists (collagen and ADP). PMC also dose-dependently inhibited the intracellular Ca2+ mobilization, whereas it did not inhibit phosphoinositide breakdown in human platelets stimulated by collagen. PMC (10 and 25 microM) significantly inhibited collagen-stimulated thromboxane A2 (TxA2) formation in human platelets. On the other hand, PMC (25 and 100 microM) did not increase the formation of cyclic AMP or cyclic GMP in platelets. Moreover, PMC (25, 100, and 200 microM) did not affect the thromboxane synthetase activity of aspirin-treated platelet microsomes. PMC (10 and 25 microM) markedly inhibited the exogenous arachidonic acid (100 microM)-induced prostaglandin E2 (PGE2) formation in the presence of imidazole (600 microM) in washed human platelets, indicating that PMC inhibits cyclo-oxygenase activity. We conclude that PMC may exert its anti-platelet aggregation activity by inhibiting cyclooxygenase activity, which leads to reduced prostaglandin formation; this, in turn, is followed by a reduction of TxA2 formation, and finally inhibition of [Ca2+]i mobilization and ATP-release.

Erythrocyte rheology

Two main subjects of erythrocyte rheology, deformation and aggregation, are discussed in detail, on the basis of biochemical structure. The close relationship between the life span (or cell aging) and the rheology of individual erythrocytes is also briefly described. A currently important problem is emphasized, that is, the molecular aspect of the dynamic cytoskeletal structure and the mechanism of its regulation. This concerns not only the rheological function and the survival of circulating erythrocytes, but also the pathophysiology of abnormal erythrocytes.