Oxidative and Nitrosative Stress in Stable Renal Transplant Recipients with Respect to the Immunosuppression Protocol - Differences or Similarities?

The Effect of Enalapril, Losartan, or Not Antihypertensive on the Oxidative Status in Renal Transplant Recipients

The clinical and biochemical improvement observed in kidney transplant (RT) recipients is remarkable. The correct functioning of the allograft depends on various factors such as the donor's age, the alloimmune response, the ischemia-reperfusion injury, arterial hypertension, and the interstitial fibrosis of the allograft, among others. Antihypertensive drugs are necessary for arterial hypertension patients to avoid or reduce the probability of affecting graft function in RT recipients. Oxidative stress (OS) is another complex pathophysiological process with the ability to alter posttransplant kidney function. The study's objective was to determine the effect of the administration of Enalapril, Losartan, or not antihypertensive medication on the oxidative state in RT recipients at the beginning of the study and one year of follow-up. All patients included in the study found significant overexpression of the oxidative damage marker to DNA and the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx). In contrast, it was found that the determination of the total antioxidant capacity decreased significantly in the final determination at one year of follow-up in all the patients who ingested Enalapril and Losartan. We found dysregulation of the oxidative state characterized mainly by oxidative damage to DNA and a significant increase in antioxidant enzymes, which could suggest a compensatory effect against the imbalance of the oxidative state.

Effect of Calcineurin Inhibitors and Mammalian Target of Rapamycin Inhibitors on the Course of COVID-19 in Kidney Transplant Recipients

Coronavirus disease 19 (COVID-19) has been an ongoing pandemic since December 2019. Unfortunately, kidney transplant recipients are a high-risk group during the disease course, and scientific data are still limited in this patient group. Beyond the dosage of immunosuppressive drugs, pharmacological immunosuppression may also alter the infection response in the COVID-19 course. The effects of immunosuppressive agents on the development and process of infection should not be decided only by determining how potent they are and how much they suppress the immune system; it is also thought that the direct effect of the virus, increased oxidative stress, and cytokine storm play a role in the pathogenesis of COVID-19 disease. There are data about immunosuppressive drugs like calcineurin inhibitors (CNI) or mammalian target of rapamycin inhibitors (mTORi) therapy related to their beneficial effects during any infection course. Limited data suggest that the use of CNI or mTORi may have beneficial effects on the process. In this hypothetical review, the probable impacts of CNI and mTORi on the pathogenesis of the COVID-19 were investigated.

Uremic Toxins, Oxidative Stress, Atherosclerosis in Chronic Kidney Disease, and Kidney Transplantation

Patients with chronic kidney disease (CKD) are at a high risk for cardiovascular disease (CVD), and approximately half of all deaths among patients with CKD are a direct result of CVD. The premature cardiovascular disease extends from mild to moderate CKD stages, and the severity of CVD and the risk of death increase with a decline in kidney function. Successful kidney transplantation significantly decreases the risk of death relative to long-term dialysis treatment; nevertheless, the prevalence of CVD remains high and is responsible for approximately 20-35% of mortality in renal transplant recipients. The prevalence of traditional and nontraditional risk factors for CVD is higher in patients with CKD and transplant recipients compared with the general population; however, it can only partly explain the highly increased cardiovascular burden in CKD patients. Nontraditional risk factors, unique to CKD patients, include proteinuria, disturbed calcium, and phosphate metabolism, anemia, fluid overload, and accumulation of uremic toxins. This accumulation of uremic toxins is associated with systemic alterations including inflammation and oxidative stress which are considered crucial in CKD progression and CKD-related CVD. Kidney transplantation can mitigate the impact of some of these nontraditional factors, but they typically persist to some degree following transplantation. Taking into consideration the scarcity of data on uremic waste products, oxidative stress, and their relation to atherosclerosis in renal transplantation, in the review, we discussed the impact of uremic toxins on vascular dysfunction in CKD patients and kidney transplant recipients. Special attention was paid to the role of native and transplanted kidney function.

Asymmetric dimethylarginine serum levels are associated with early mortality after allogeneic stem cell transplantation

Increasing evidence suggests that endothelial cell distress is associated with mortality after allogeneic stem cell transplantation and acute graft-versus-host disease. Asymmetric dimethylarginine is an endogenous nitric oxide synthase inhibitor that induces endothelial cell dysfunction. We analyzed the impact of pre-transplant serum levels of asymmetric dimethylarginine on outcome after allogeneic stem cell transplantation. Since acute graft-versus-host disease and its treatment are major contributors to post-transplant mortality, the effect of asymmetric dimethylarginine on outcome measures was also assessed after onset of acute graft-versus-host disease. A total of 938 patients allografted at two centers between 2002 and 2013 were included in the retrospective study. In multivariable models, higher pre-transplant asymmetric dimethylarginine levels were significantly associated with an increased risk of non-relapse mortality (hazard ratio 1.43 per 1-log₂ increase, P=0.005) but not with relapse (hazard ratio 1.21, P=0.109) within the first year after transplantation. This translated into worse overall survival (hazard ratio 1.45, P<0.0001) and shorter progression-free survival (hazard ratio 1.30, P=0.002) in the first year after transplantation. Higher pre-transplant asymmetric dimethylarginine levels were also associated with shorter overall survival (hazard ratio 1.46, P=0.001) and progression-free survival (hazard ratio 1.32, P=0.010) and higher non-relapse mortality (hazard ratio 1.36, P=0.042) within 1 year after the onset of acute graft-versus-host disease. Taken together, our data indicate an association between pre-transplant asymmetric dimethylarginine status and early non-relapse mortality in allografted patients, both overall and after the onset of acute graft-versus-host disease. These findings underline the relevance of endothelial dysfunction for transplant complications.

Alterations of HDL Particles in Children with End-stage Renal Disease

Background

Unfavorable lipid profile presents one of most important risk factor for cardiovascular disease in renal pathology. Myeloperoxidase (MPO) as enzyme which oxidizes lipoproteins and paraoxonase1 (PON1) as anti-oxidative enzyme have been involved in pathogenesis of cardiovascular disease. In the present study we sought to assess oxidative stress status, lipoprotein subclasses distribution as well as functionality of high density lipoprotein (HDL) trough MPO/PON1 ratio in children with chronic kidney disease (CKD) and children after renal transplantation.

Methods

PON1 activity and oxidative stress parameters were measured spectrophotometrically, while MPO concentration was determined using immunoassay. Separation of lipoprotein subclasses was performed by vertical gradient gel electrophoresis in 19 children with different stage of CKD and 19 post-transplantation patients (PT).

Results

CKD patients had increased MPO/PON1 ratio and higher prevalence of smaller HDL subclasses when compared to PT subjects. Also, there was a significant positive correlation between MPO level and MPO/PON1 ratio with relative proportion of smaller HDL subclasses.

Conclusion

Children with CKD have impaired HDL distribution that is improved after kidney transplantation. Since that measurement of HDL distribution and functionality are not routinely available, MPO/PON1 ratio may be useful marker that could provide necessary information.

Downregulation of AdipoR1 is Associated with increased Circulating Adiponectin Levels in Serbian Chronic Kidney Disease Patients

BACKGROUND

Since the rise in plasma adiponectin levels in chronic kidney disease (CKD) patients has not yet been elucidated, we sought to investigate if patients on hemodialysis (HD) have altered expression of adiponectin receptors in peripheral blood mononuclear cells (PBMCs) compared to healthy subjects.

METHODS

This study included 31 patients with chronic kidney disease on HD and 33 healthy subjects (CG). Circulating adiponectin levels were measured by ELISA while AdipoR1 and AdipoR2 mRNA levels in PBMCs were determined by real-time PCR.

RESULTS

Plasma adiponectin levels were significantly higher in patients compared to control group (P=0.036). After adjustment for age, BMI and creatinine, this difference became even more significant (P=0.004). In both groups adiponectin correlated with creatinine (CG: r=-0.472, P=0.006; HD: r=-0.375, P=0.038), triglycerides (CG: r=- 0.490, P=0.004; HD: r=-0.488, P=0.005), insulin (CG: r=-0.386, P=0.038; HD: r=-0.506, P=0.012) and high density lipoprotein cholesterol (HDL-C) (CG: r=-0.672, P<0.001; HD: r=-0.584, P=0.001). Significantly lower expression of PBMCs AdipoR1 mRNA was found in patients compared to CG (P=0.034), while AdipoR2 mRNA levels were similarly expressed in PBMCs in both groups.

CONCLUSIONS

Complex pathological processes in CKD cause downregulation of AdipoR1 which could ultimately influence AdipoR1 protein levels leading to a state of ≫adiponectin resistance≪.

Association of GSTO1 and GSTO2 Polymorphism with Risk of End-Stage Renal Disease Development and Patient Survival

Background

Oxidative stress in patients with end-stage renal disease (ESRD) is associated with long-term cardiovascular complications. The cytosolic family of glutathione S-transferases (GSTs) is involved in the detoxication of various toxic compounds and antioxidant protection. GST omega class members, GSTO1 and GSTO2 possess, unlike other GSTs, dehydroascorbate reductase and deglutathionylation activities. The aim of this study was to clarify the role of genetic polymorphisms of GSTO1 (rs4925) and GSTO2 (rs156697) as risk determinants for ESRD development, as well as in the survival of these patients.

Methods

A total of 199 patients and 199 healthy subjects were included in the study and genotyped for both GSTO1 and GSTO2 polymorphism. Protein thiol and carbonyl groups as markers of protein oxidative damage were determined spectrophotometrically. Cox proportional hazard model and Kaplan-Meier analysis were performed to investigate the role of GSTO1 and GSTO2 genetic polymorphism on mortality of ESRD patients during the follow-up period (36 month).

Results

Individuals carrying the variant GSTO2 GG genotype were at 2.45-fold higher risk of ESRD development compared to the wild type GSTO2 AA genotype (OR=2.45; 95%CI=1.18–5.07; p=0.016). The results of GSTO1/GSTO2 haplotype analysis showed that the haplotype combination of GSTO1 (*A)/GSTO2 (*A) (GSTO1 variant/GSTO2 wild type allele) was protective for ESRD (OR=0.23 95%CI=0.12-0.44, p=0.001). Patients carrying at least one GSTO1 reference allele have shorter mean overall (Log rank=2.844, p =0.241) and cardiovascular survival probability (Log rank=4.211, p=0.122).

Conclusions

GSTO polymorphisms have been shown to act as significant markers in assessing the risk of ESRD development and patients’ survival.

NO-Synthase Activity in Patients with Coronary Heart Disease Associated with Hypertension of Different Age Groups

Background

Coronary heart disease is the leading cause of death and disability worldwide. Hypertension is a major independent risk factor for the development of CHD. Abnormalities in NO generation or activity have been proposed as a major mechanism of CHD. The purpose of this article is to determine the activity of eNOS and iNOS in patients with isolated CHD and CHD associated with HT of different age groups.

Methods

Fifty patients with isolated CHD and 42 patients with CHD associated with HT were enrolled in this study. NOS activity was determined by nitrite anion formed in the reaction.

Results

A statistically significant increase in iNOS activity is observed in elderly donors. In patients with isolated coronary heart disease cNOS activity is statistically significantly reduced with respect to the control group. The reduction of enzymatic activity of cNOS is more expressed in elderly patients than in middle-aged patients with coronary heart disease. Alterations in eNOS activity are more expressed in patients with coronary heart disease associated with hypertension than in patients with isolated coronary heart disease. Against the background of cNOS inhibition in the patients, a sharp increase in iNOS activity is observed.

Conclusions

It has been shown that disturbance of endothelial function in patients with coronary heart disease associated with hypertension is characterized by reduced endothelial NO synthesis by cNOS and increased systemic NO synthesis due to increased iNOS activity. It has been found that the lack of endothelial NO and hyperproduction of »harmful« NO by iNOS are more expressed in elderly patients.