The Role of 20-HETE, COX, Thromboxane Receptors, and Blood Plasma Antioxidant Status in Vascular Relaxation of Copper-Nanoparticle-Fed WKY Rats

Decreased vascular contraction and changes in oxidative state in middle-aged Wistar rats after exposure to increased levels of dietary zinc

Both copper and zinc are known to be important for maintaining health, but most research has focused on deficiencies of these elements. Recent studies have shown that high levels of Cu can be toxic, especially to the cardiovascular (CV) system. However, little research has been done on the effects of higher levels of Zn on the CV system. In this study, male Wistar rats aged 12 months were given a diet with twice the recommended daily allowance of zinc (31.8 mg/kg of diet) and compared to a control group (15.9 mg/kg of diet) after 8 weeks. Blood plasma and internal organs of both groups were examined for levels of copper, zinc, selenium and iron, as well as several key enzymes. Aortic rings from both groups were also examined to determine vascular functioning. There were very few changes in the vascular system functioning after chronic exposure to zinc, and only one enzyme, heme oxygenase-1 (HO-1) was elevated, whereas vascular contraction to noradrenaline decreased with no changes in vasodilation to acetylcholine. Of the micronutrients, zinc and selenium were elevated in the blood plasma, while copper decreased. Meanwhile, the total antioxidant status increased. These were not observed in the liver. Therefore, it is proposed that there is a mechanism in place within the vascular system to protect against the overproduction of heme, caused by chronic zinc exposure.

Prolonged Copper Supplementation Modified Minerals in the Kidney, Liver and Blood, and Potentiated Oxidative Stress and Vasodilation of Isolated Aortic Rings in Young Wistar Rats

BACKGROUND

Previous studies have highlighted that copper supplementation at 200% of the recommended daily dietary allowance modified vascular contraction and relaxation through increased reactive oxygen species (ROS) and prostaglandin formation, which modified the antioxidant status of middle-aged Wistar rats.

METHODS

In this study, young (1 month old) male Wistar rats (n/group = 10) received a diet supplemented with 6.45 mg copper/kg (100% of daily recommendation-Group A) for 8 weeks. The experimental group received 12.9 mg copper/kg of diet (200% of the daily recommendation-Group B).

RESULTS

Experimental supplementation with 200% copper modified the copper concentration in the blood (1.21-fold, p = 0.04), liver (1.15-fold, p = 0.032), and kidneys (1.23-fold, p = 0.045), potentiated the ROS formation in the aortic rings, and enhanced the sensitivity of the aortic rings to the vasodilator acetylcholine. We observed an increased participation of nitric oxide (NO) derived from inducible NO synthase (iNOS) in vascular contraction and a decreased net effect of vasodilator prostanoids derived from cyclooxygenase-2 in vascular relaxation. In rat kidneys, the concentrations of potassium (1.08-fold, p = 0.001) and iron (1.13-fold, p = 0.046) were higher, while, calcium (0.88-fold, p = 0.001) and chromium (0.77-fold, p = 0.005) concentrations were lower. In the rat liver, magnesium (1.06-fold, p = 0.012) was higher. No differences were observed in the concentrations of sodium, zinc, manganese, selenium, cobalt, molybdenum, and vanadium. The antioxidant activity of water- and lipid-soluble compounds; total antioxidant status in the blood; and superoxide dismutase, catalase, and malondialdehyde levels in the heart did not change.

CONCLUSIONS

In young rats, prolonged supplementation with 200% copper had a lesser effect than anticipated on oxidative stress and vascular reactivity. Detailed data on the status of trace elements and their interactions in patients of different age groups are strongly required for effective nutritional and therapeutic intervention.

Dietary Supplements in Cardiovascular and Metabolic Diseases

Recent research has sparked increasing interest in the effects of dietary supplements on cardiovascular and metabolic disorders [...].

The Effect of an Elevated Dietary Copper Level on the Vascular Contractility and Oxidative Stress in Middle-Aged Rats

Copper (Cu), being an essential mineral, plays a crucial role in maintaining physiological homeostasis across multiple bodily systems, notably the cardiovascular system. However, an increased Cu level in the body may cause blood vessel dysfunction and oxidative stress, which is unfavorable for the cardiovascular system. Middle-aged (7-8 months old) male Wistar rats (n/group = 12) received a diet supplemented with 6.45 mg Cu/kg (100% of the recommended daily dietary quantity of copper) for 8 weeks (Group A). The experimental group received 12.9 mg Cu/kg of diet (200%-Group B). An ex vivo study revealed that supplementation with 200% Cu decreased the contraction of isolated aortic rings to noradrenaline (0.7-fold) through FP receptor modulation. Vasodilation to sodium nitroprusside (1.10-fold) and acetylcholine (1.13-fold) was potentiated due to the increased net effect of prostacyclin derived from cyclooxygenase-1. Nitric oxide (NO, 2.08-fold), superoxide anion (O2•-, 1.5-fold), and hydrogen peroxide (H2O2, 2.33-fold) measured in the aortic rings increased. Blood serum antioxidant status (TAS, 1.6-fold), Cu (1.2-fold), Zn (1.1-fold), and the Cu/Zn ratio (1.4-fold) increased. An increase in Cu (1.12-fold) and the Cu/Zn ratio (1.09-fold) was also seen in the rats' livers. Meanwhile, cyclooxygenase-1 (0.7-fold), cyclooxygenase-2 (0.4-fold) and glyceraldehyde 3-phosphate dehydrogenase (0.5-fold) decreased. Moreover, a negative correlation between Cu and Zn was found (r = -0.80) in rat serum. Supplementation with 200% Cu did not modify the isolated heart functioning. No significant difference was found in the body weight, fat/lean body ratio, and organ weight for either the heart or liver, spleen, kidney, and brain. Neither Fe nor Se, the Cu/Se ratio, the Se/Zn ratio (in serum and liver), heme oxygenase-1 (HO-1), endothelial nitric oxide synthase (eNOS), or intercellular adhesion molecule-1 (iCAM-1) (in serum) were modified. Supplementation with 200% of Cu potentiated pro-oxidant status and modified vascular contractility in middle-aged rats.

The Interaction of Dietary Pectin, Inulin, and Psyllium with Copper Nanoparticle Induced Changes to the Cardiovascular System

We aimed to analyze how supplementation with a standard (recommended, 6.5 mg/kg) or enhanced (two-times higher, 13 mg/kg) dose of copper (Cu), in the form of nanoparticles (NPs) along with dietary intervention via the implementation of diverse types of fiber, affects the cardiovascular system in rats. Nine-week-old male Wistar Han rats (n/group = 10) received, for an additional 6 weeks, a controlled diet with cellulose as dietary fiber and ionic Cu (in the form of carbonate salt). The experimental groups received cellulose, pectin, inulin, and psyllium as dietary fiber, together with CuNPs (6.5 or 13 mg/kg diet). After the experimental feeding, samples of blood, hearts, and thoracic arteries were collected for further analysis. Compared to pectin, and under a standard dose of CuNPs, inulin and psyllium beneficially increased the antioxidant capacity of lipid- and water-soluble compounds in the blood, and decreased heart malondialdehyde. Moreover, pectin decreased heart catalase (CAT) and cyclooxygenase (COX)-2 in the aortic rings compared to inulin and psyllium under standard and enhanced doses of copper. When the dose of CuNPs was enhanced, inulin and psyllium potentiated vasodilation to acetylcholine by up-regulation of COX-2-derived vasodilator prostanoids compared to both cellulose and pectin, and this was modulated with selective inducible nitric oxide synthase (iNOS) inhibitor for psyllium only. Moreover, inulin decreased heart CAT compared to psyllium. Our results suggest that supplementation with dietary fiber may protect the vascular system against potentially harmful metal NPs by modulating the antioxidant mechanisms.

Copper and Zinc Particles as Regulators of Cardiovascular System Function-A Review

Copper and zinc are micronutrients that play a crucial role in many cellular pathways, act as cofactors in enzymatic systems, and hence, modulate enzyme activity. The regulation of these elements in homeostasis is precisely controlled by various mechanisms. Superoxide dismutase (SOD) is an enzyme requiring both copper and zinc for proper functioning. Additionally, there is an interaction between the concentrations of copper and zinc. Dietary ingestion of large amounts of zinc augments intestinal absorption of this trace element, resulting in copper deficiency secondary to zinc excess. The presence of an overabundance of copper and zinc has a detrimental impact on the cardiovascular system; however, the impact on vascular contractility varies. Copper plays a role in the modulation of vascular remodeling in the cardiac tissue, and the phenomenon of cuproptosis has been linked to the pathogenesis of coronary artery disease. The presence of copper has an observable effect on the vasorelaxation mediated by nitric oxide. The maintenance of proper levels of zinc within an organism influences SOD and is essential in the pathogenesis of myocardial ischemia/reperfusion injury. Recently, the effects of metal nanoparticles have been investigated due to their unique characteristics. On the other hand, dietary introduction of metal nanoparticles may result in vascular dysfunction, oxidative stress, and cellular DNA damage. Copper and zinc intake affect cardiovascular function, but more research is needed.

Dietary Effects of Chromium Picolinate and Chromium Nanoparticles in Wistar Rats Fed with a High-Fat, Low-Fiber Diet: The Role of Fat Normalization

We aimed to evaluate how feeding a high-fat-low-fiber (F) diet to rats and dietary intervention with the implementation of a standard-fat-and-fiber (S) diet affects the response of the cardiovascular system to chromium (III) picolinate (Cr-Pic) and, alternatively, chromium nanoparticles (Cr-NPs). Young male Wistar Han rats (n/group = 12) from either the fatty group (18 weeks on F diet) or the intervention group (9 weeks on F diet + 9 weeks on S diet) received a pharmacologically relevant dose of 0.3 mg Cr/kg body weight in the form of Cr-Pic or Cr-NPs for 9 weeks. Our study on rats confirmed the pro-inflammatory effect of an F diet administered for 18 weeks. In the intervention group, both Cr-Pic and Cr-NPs decreased heart glutathione ratio (GSH+GSSG), enhanced participation of nitric oxide (NO) derived from inducible NO synthase (iNOS) in vascular relaxation to acetylcholine (ACh), increased the vasodilator net effect of cyclooxygenase-2 (COX-2)-derived prostanoids, and increased the production of superoxide anion (O₂^.-) in aortic rings. Meanwhile, in the fatty group, there was increased heart superoxide dismutase (SOD), decreased heart catalase (CAT), and reduced sensitivity in pre-incubated aortic rings to endogenous prostacyclin (PGI₂). The factors that significantly differentiated Cr-NPs from Cr-Pic were (i) decreased blood antioxidant capacity of water-soluble compounds (0.75-fold, p = 0.0205), (ii) increased hydrogen peroxide (H₂O₂) production (1.59-fold, p = 0.0332), and (iii) modified vasodilator response due to PGI₂ synthesis inhibition (in the intervention group) vs. modified ACh-induced vasodilator response due to (iv) COX inhibition and v) PGI₂ synthesis inhibition with thromboxane receptor blockage after 18 weeks on F diet (in the fatty group). Our results show that supplementation with Cr-Pic rather than with Cr-NPs is more beneficial in rats who regularly consumed an F diet (e.g., for 18 weeks). On the contrary, in the intervention group (9 weeks on F diet + 9 weeks of dietary fat normalization (the S diet)), Cr-Pic and Cr-NPs could function as pro-oxidant agents, initiating free-radical reactions that led to oxidative stress.

Effect of Copper Nanoparticles in the Diet of WKY and SHR Rats on the Redox Profile and Histology of the Heart, Liver, Kidney, and Small Intestine

The aim of this experiment was to test the effect of the partial or complete replacement of traditional CuCO₃ in the diet of rats with copper nanoparticles (CuNPs) on the biochemical parameters, redox status, and histomorphometry of their tissues. Normotensive male Wistar–Kyoto rats (WKY) were allocated to three groups. Three analogous groups of spontaneously hypertensive rats (SHR) were also formed. The WKY and SHR rats received copper in a standard daily dose—6.5 mg/kg CuCO₃ or CuNPs (100% replacement) or 3.25 mg/kg CuCO₃ plus 3.25 mg/kg CuNPs (50% replacement)—for 8 weeks. Next, blood, heart, small intestine, liver, and kidney samples were collected. The activity of alanine aminotransferase, aspartate aminotransferase, creatine kinase, and gamma-glutamyl transferase and the content of creatinine and urea acid were measured in the plasma. The collected tissues were subjected to a histological evaluation, and redox status parameters (catalase and superoxide dismutase activity, malondialdehyde and glutathione content) were determined. The replacement of CuCO₃ with CuNPs in the diet may exacerbate the negative changes induced by hypertension in the heart, liver, and intestines. However, it seems that it is only in the case of the liver where the observed changes may be due to an increase in oxidative reactions resulting from the inclusion of CuNPs.