Ultrastructural alterations in endothelial mitochondria are associated with enhanced nitrotyrosine accumulation and progressive reduction of VEGF expression in sequential protocol renal allograft biopsies with calcineurin inhibitor toxicity

The impact of long-term exposure to tacrolimus on chronic kidney disease after lung transplantation: A retrospective analysis from a single transplantation center

BACKGROUND

Chronic kidney disease (CKD) is a progressive and irreversible complication in lung transplant patients who have received long-term treatment with tacrolimus. This study aimed to verify long-term tacrolimus exposure values in CKD progression.

METHODS

We retrospectively analyzed the clinical data of adult lung transplant recipients performed at our center between 2012 and October 2015. Patients who completed the 5-year follow-up period were enrolled in this study. CKD was defined as an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m².

RESULTS

Eighty patients were analyzed. Compared with baseline (109 ± 38.1 mL/min/1.73 m2), the average eGFR values of our patients gradually decreased during the fifth-year post transplantation (46.5%, 58.3 ± 28.3 mL/min/1.73 m2), and the decline in eGFR values was particularly pronounced in the first year (31.2%, 74.6 ± 28.91 mL/min/1.73 m2). Moreover, 10 (12.7%), 21 (26.9%), 24 (31.2%), 28 (41.2%), and 48 (60%) patients had eGFR <60 mL/min/1.73 m² at 3, 6, 1, 3, and 5 years after lung transplantation (LT), respectively. A significant negative correlation was found between tacrolimus dose and eGFR 6 months after LT (P = 0.0414). We found no correlation between the serum tacrolimus concentration and CKD progression.

CONCLUSION

eGFR constantly decreased and the incidence of CKD increased during the 5-year follow-up period after LT. The tacrolimus dose had a significant negative correlation with eGFR at 6 months after LT. Meanwhile, whole-blood tacrolimus trough concentrations were not correlated with eGFR decline. When possible, lower dosing within 1 year after LT can reduce potential nephrotoxic side effects.

Influence of irrigation regimes on competition indexes of winter and summer intercropping system under semi-arid regions of Pakistan

An assessment of the competitive indexes in intercropping of different winter and summer based intercropping systems were studied, with the aim of increasing the productivity of these crops. Four winter crops, wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), fababean (Vicia faba) and rapeseed (Brassica napus) and four summer crops, sorghum (Sorghum bicolor L.), pearl millet (Pennisetum typhoidum L.), pigeonpea (Cajanus cajan L.) and mungbean (Vigna radiate L.) were grown under two irrigation regimes with the pattern of two crops in each intercropping system, at Agronomy Research Farm, The University of Agriculture, Peshawar, Pakistan in both winter and summer season during 2015-16 to 2016-17. The results showed that higher grain yield (kg ha^-1) were recorded under sole cropping than intercropping. Higher grain yield was recorded in sole cropping, for all four crops. All crops grown in intercropping produced comparatively higher grains head^-1 and seeds pod^-1 than sole crop except pigeonpea. Intercropping systems were performed different in term of competition indexes which determined land utilization efficiency. Competition indexes revealed that in winter season wheat intercropped with fababean showed highest advantages of intercropping in term of land equivalent ratio (30%), relative crowding co-efficient (60%), actual yield loss (60%), area time equivalent ratio (27%), land utilization efficiency (83%), intercropping advantages (1060), monetary advantage index (Pakistani rupees (PKR) 46456) and system productivity index (3684) while in summer sorghum/pearl millet intercropped with pigeonpea was the most dominant intercropping systems in term of relative  crowding co-Efficient (40%), actual yield loss (50%), land utilization efficiency (60%) intercropping advantages (1150) and system productivity index (1914). Aggressivity and competition ratio showed that cereals especially barley in winter and sorghum in summer season was highly competitive crops in the intercropping system. Most of the competition indexes values were higher for winter crops under limited irrigated condition while in case of summer crops intercropping indexes were higher under full irrigated condition. It was concluded that wheat intercropped with fababean, and sorghum/millet intercropped with mung bean was the most successful intercropping systems in winter and summer seasons, respectively under both irrigation regimes, for the semiarid region of Pakistan.

Calcineurin Inhibitor Nephrotoxicity Through the Lens of Longitudinal Histology: Comparison of Cyclosporine and Tacrolimus Eras

BACKGROUND

The contribution of calcineurin inhibitors (CNI) nephrotoxicity to progressive kidney transplant injury remains debated, with little long-term data from the modern tacrolimus (TAC) era using lower doses.

METHODS

This longitudinal cohort study evaluated histological evidence of CNI nephrotoxicity from normal donor kidneys of successful kidney-pancreas transplant recipients during cyclosporine (CSA) and TAC eras, analyzed by intention-to-treat.

RESULTS

From 200 patients, 1622 adequate prospective protocol (84.3%) and indication (15.7%) kidney biopsies yielded 8.1 ± 4.1 samples per patient, over 7.4 ± 4.4 years posttransplant. The TAC era demonstrated less rejection and reduced early immune-mediated tubular damage, compared with CSA (P < 0.001). The incidences of acute mild arteriolopathy, striped interstitial fibrosis, glomerular congestion, and tubular microcalcification were all greater with CSA (hazard ratios of 1.70, 9.35, and 3.78, respectively) and maximal within the first posttransplant year, compared with TAC-treated patients (P < 0.001). However, the 1-, 5-, and 10-year prevalence moderate arteriolar hyalinosis was similar: CSA was 5.4%, 38.4%, and 79.1%; and TAC was 4.3%, 33.6% and 77.2%, respectively (P = NS). Morphometric measurement demonstrated lumenal narrowing from inwards collapse of hyalinized arteriolar walls unable to maintain its structural integrity. Severe hyalinosis was calculated to reduce arteriolar blood flow to 20 ± 34% of normal. Severity of arteriolar hyalinosis correlated with contemporaneous glomerulosclerosis (r = 0.44, P < 0.001), and subsequent progression in 1356 sequential biopsy pairs, consistent with glomerular ischemia.

CONCLUSIONS

Tacrolimus-based therapy appeared superior to the CSA era, with less early CNI nephrotoxicity and fewer rejection episodes, but comparable chronic arteriolar toxicity. Calcineurin inhibitors are imperfect long-term maintenance immunosuppressive agents because of frequent and irreversible chronic toxicity.

Calcineurin-inhibition Results in Upregulation of Local Renin and Subsequent Vascular Endothelial Growth Factor Production in Renal Collecting Ducts

BACKGROUND

Tacrolimus (Tac) and Cyclosporine A (CyA) calcineurin inhibitors (CNIs) are 2 effective immunosuppressants which are essential to prevent allograft rejection. Calcineurin inhibitors are known to be nephrotoxic. However, the precise mechanism of nephrotoxicity is not fully understood. In this study, we investigated the in vivo effects of CNIs on the local renal renin-angiotensin system in the collecting duct (CD).

METHODS

Three-week-old mice were treated with either vehicle, CyA (2 mg/kg per day), Tac (0.075 mg/kg per day), CyA + Aliskiren (25 mg/kg per day), or Tac + Aliskiren for 3 weeks. Serum creatinine was measured. Renin and vascular endothelial growth factor (VEGF) contents in CD were evaluated with flow cytometry and multiphoton microscopy. The diameter of vessels was assessed with multiphoton microscopy, and the amount of renal collagen was determined by real-time polymerase chain reaction and Masson staining.

RESULTS

The elevated level of serum creatinine in CNI groups was abolished by Aliskiren. Flow cytometric analysis found elevated renin content in principal cells, which was prevented by Aliskiren. This result was further confirmed with multiphoton microscopy. The VEGF content in CD correlated with reduced capillary diameter and with the formation of fibrotic islands.

CONCLUSIONS

Calcineurin inhibitors induce production of renin in the CD that may contribute to decreased renal blood flow. In turn, CD responds with increased VEGF production, resulting in disproportional vessel growth, further worsening the local hypoxia and striped fibrosis surrounding the CDs. Aliskiren, a direct renin inhibitor blocks these effects and improves CNI-induced nephropathy by decreasing renin production in the CDs. Our data suggest that Aliskiren may be used for the prevention of CNI nephrotoxicity.

A comparative study on renal biopsy before and after long-term calcineurin inhibitors therapy: an insight for pathogenesis of its toxicity

Calcineurin inhibitors (CNIs) are effective immunosuppressive agents for the successful treatment of childhood steroid-resistant nephrotic syndrome (SRNS). Because these patients require long-term treatment, the identification of early markers of CNI-induced nephrotoxicity (CNIN) is imperative. The monitoring of CNI trough levels, serum creatinine, and glomerular filtration rate is not an accurate marker of CNIN. The present study has been undertaken to identify early markers of CNIN in SRNS patients. Twenty-four pediatric SRNS patients were included with paired renal biopsies, before initiation (time zero biopsy) and at least 1 year after CNI therapy (protocol renal biopsy) with standard dosage. Semiquantitative morphologic grading of the histologic features was done for assessing CNIN. Immunohistochemical markers for oxidative stress (nitrotyrosine [NT]), fibrogenic cytokine (transforming growth factor β1 [TGF-β1]), and endothelial injury (endothelial nitric oxide synthase [eNOS]) were evaluated. In addition, ultrastructural study was done to assess mitochondrial injury in endothelial and tubular epithelial cells. The protocol renal biopsies in comparison with time zero biopsies showed significant increase in glomerulosclerosis, juxtaglomerular apparatus hyperplasia, tubular atrophy, interstitial fibrosis, arteriolar hyalinosis, and smooth muscle vacuolization (P < .05 - P < .001). Significantly higher immunoexpression of eNOS (91.6%), NT (71%), and TGF-β1 (87.5%) was noted in posttreatment biopsies. Mean mitochondrial injury grade among post-CNI cases in endothelial cells and proximal tubular cells was 2.28 and 1.4, whereas in pre-CNI, it was 0.28 and 0.27, respectively. We propose that immunohistochemical overexpression of NT, eNOS, and TGF-β1 is an early marker of CNIN. Endothelial and proximal tubular mitochondrial injury may play an important role in the pathogenesis of CNIN.

Stabilization of oxidative stress 1 year after kidney transplantation: effect of calcineurin immunosuppressives

Kidney transplantation (KT) is one of the best treatments for patients with chronic renal disease. It leads to improved kidney function, but the oxidative stress (OS) is only partially eliminated after KT. This study evaluated the effect of KT on outcomes, such as (a) specific kidney functions, (b) metabolic parameters, as well as (c) OS-related markers in 70 patients (46 males, 24 females; mean age = 54 ± 11) before and 1 year after KT. Post KT, the patients were divided into two groups: those receiving only cyclosporine A (N = 36) and those receiving only tacrolimus (N = 34). Improved kidney function (creatinine, urea, and glomerular filtration rate) and biochemical and hematological parameters were found 1 year after KT. OS-related markers (total antioxidant capacity, advanced oxidation protein, and lipid peroxidation products) decreased, but glutathione level increased after KT. Alterations in superoxide dismutase and catalase activities were also found. Glutathione peroxidase levels were unchanged. The level of oxidized low-density lipoprotein was surprisingly, not significantly increased. There was no significant difference between calcineurin inhibitors in any of the measured parameters. Improved renal function after KT is linked to reduction in OS but independent of immunosuppressive therapy.