Gender Differences in the Acute Kidney Injury to Chronic Kidney Disease Transition.

This study evaluated if there is a sexual dimorphism in the acute kidney injury (AKI) to chronic kidney disease (CKD) transition and the time-course of the potential mechanisms involved in the dimorphic response. Female and male rats were divided into sham-operated or underwent 45-min renal ischemia (F + IR, and M + IR). All groups were studied at 24-h and 1, 2, 3, or 4-months post-ischemia. Additionally, oophorectomized rats were divided into sham or IR groups. After 24-h, AKI extent was simllar in females and males, but female rats exhibited less oxidative stress and increased renal GSH content. After 4-months and despite similar AKI, the M + IR group developed CKD characterized by proteinuria, tubulointerstitial fibrosis, glomerular hypertrophy, increased oxidative stress and a reduction in HIF1α and VEGF from the 1st-month and persisting throughout the time-course studied. Interestingly, the F + IR group did not develop CKD due to lesser oxidative stress and increased eNOS, TGFß and HIF1α mRNA levels from the 1st-month after IR. Whereas, oophorectomized rats did develop CKD. We found a sexual dimorphic response in the AKI to CKD transition. Early antioxidant defense and higher TGFß, HIF1α and eNOS were among the renoprotective mechanisms that the F + IR group demonstrated.

AT1 receptor antagonism before ischemia prevents the transition of acute kidney injury to chronic kidney disease.

Despite clinical recovery of patients from an episode of acute kidney injury (AKI), progression to chronic kidney disease (CKD) is possible on long-term follow-up. However, mechanisms of this are poorly understood. Here, we determine whether activation of angiotensin-II type 1 receptors during AKI triggers maladaptive mechanisms that lead to CKD. Nine months after AKI, male Wistar rats develop CKD characterized by renal dysfunction, proteinuria, renal hypertrophy, glomerulosclerosis, tubular atrophy, and tubulointerstitial fibrosis. Renal injury was associated with increased oxidative stress, inflammation, α-smooth muscle actin expression, and activation of transforming growth factor ß; the latter mainly found in epithelial cells. Although administration of losartan prior to the initial ischemic insult did not prevent or reduce AKI severity, it effectively prevented eventual CKD. Three days after AKI, renal dysfunction, tubular structural injury, and elevation of urinary biomarkers were present. While the losartan group had similar early renal injury, renal perfusion was completely restored as early as day 3 postischemia. Further, there was increased vascular endothelial growth factor expression and an early activation of hypoxia-inducible factor 1 α, a transcription factor that regulates expression of many genes that help reduce renal injury. Thus, AT1 receptor antagonism prior to ischemia prevented AKI to CKD transition by improving early renal blood flow recovery, lesser inflammation, and increased hypoxia-inducible factor 1 α activity.

Mild ischemic injury leads to long-term alterations in the kidney: amelioration by spironolactone administration.

Administration of the mineralocorticoid receptor antagonist spironolactone prevents the development of chronic kidney disease (CKD) after a severe ischemic injury. However, whether brief periods of ischemia lead to CKD and whether spironolactone administration after ischemia may be a useful therapeutic strategy to prevent the gradual deterioration of structure and function remains unexplored. Nineteen male Wistar rats were divided into four groups: rats that underwent renal bilateral ischemia for 10, 20, or 45 min were compared with sham operated rats. Additionally, thirteen male Wistar rats that underwent renal bilateral ischemia for 20 min were divided into an untreated ischemic group (I) and two groups receiving spironolactone, 20 mg/kg by gavage, at either 0 (Sp0) or 1.5-h after ischemia (Sp1.5). The rats were followed up and studied after 9 months. Mild (20 min) and severe (45 min) ischemia induced a progressive increase in proteinuria at varying magnitudes, whereas minor ischemia (10 min) did not modify proteinuria. CKD induced by moderate ischemia was characterized by renal hypertrophy and tubulointerstitial fibrosis. These effects were associated with activation of the transforming growth factor ß (TGFß) signaling pathway and up-regulation of endothelin receptor A (ETA) and alpha smooth muscle actin (αSMA). Spironolactone treatment immediately or 1.5-h after the ischemic insult prevented the onset of these disorders. Our results show that moderate ischemic insult leads to long-term structural and molecular changes that may compromise renal function in later stages. Additionally, we demonstrate that spironolactone administration after mild ischemia prevents this detrimental effect.

Epigenetic regulation in the acute kidney injury to chronic kidney disease transition.

Epigenetic modifications have emerged as a new, important contributor to gene expression regulation in both normal and pathophysiological conditions. Epigenetics have been studied in many diseases and conditions such as acute kidney injury (AKI), a syndrome with a high prevalence that carries a poor prognosis with increased morbidity and mortality. In addition, it has recently been shown that AKI increases the risk for the development of chronic kidney disease (CKD). The specific molecular mechanisms by which AKI increases the risk of CKD and end stage renal disease (ESRD) remain unknown, although there is new evidence supporting a role of epigenetic changes. The most studied epigenetic regulations in AKI are chromatin compaction, DNA methylation, and histone acetylation/deacetylation. These modifications predominantly increase the production of pro-inflammatory and profibrotic cytokines such as: monocyte chemoattractant protein-1 (MCP-1), complement protein 3 (C3), transforming growth factor ß (TGF-ß) that have been shown for perpetuating inflammation, promoting epithelial-to-mesenchymal transition (EMT) and ultimately causing renal fibrosis. A review of epigenetic mechanisms, the pathophysiology of AKI and recent studies that implicate epigenetic modifications in AKI and in the transition to CKD are discussed below.

Spironolactone prevents chronic kidney disease caused by ischemic acute kidney injury.

Acute kidney injury (AKI) has been recognized as a risk factor for the development of chronic kidney disease (CKD). Aldosterone has a critical role in promoting renal injury induced by ischemia. Here, we evaluated whether spironolactone administered before or after AKI caused by ischemia protects against CKD. In the first set of experiments, Wistar rats underwent a sham operation without or with prior spironolactone treatment, or underwent 45 minutes of bilateral renal ischemia without or with spironolactone treatment before ischemia and assessed over 270 days. The second set of rats received low (20 mg/kg) or high (80 mg/kg) doses of spironolactone at three different times after the sham operation or bilateral renal ischemia and were assessed after 90 days. Untreated animals developed CKD following ischemia-induced AKI as characterized by a progressive increase in proteinuria, renal dysfunction, podocyte injury, glomerular hypertrophy, and focal sclerosis. This was associated with increased oxidative stress, an upregulation of tumor growth factor (TGF)-ß, followed by upregulation of the TGF-ß downstream effectors phospho-Smad3, collagen I, fibronectin, and proinflammatory cytokines. Treatment with spironolactone either before or after ischemia prevented subsequent CKD by avoiding the activation of fibrotic and inflammatory pathways. Thus, spironolactone may be a promising treatment for the prevention of AKI-induced CKD.

De Novo Donor-Specific HLA Antibody Development and Peripheral CD4(+)CD25(high) Cells in Kidney Transplant Recipients: A Place for Interaction?

The aim of this study was to determine whether the abundance of regulatory T cells (Tregs) (CD4(+)CD25(high)) affects the de novo development of anti-HLA donor-specific antibodies (DSAs) in kidney transplant recipients (KTRs). Methods. Unsensitized (PRA ≤ 10%, no DSA) adult primary KTRs who received a living (83%) or deceased (17%) KT in our Institution during 2004/2005 were included. DSA testing was performed monthly, and Tregs were quantified by flow cytometry every 3 months, during the 1st year after KT. All patients received triple drug immunosuppressive therapy (CNI + MMF or AZA + PDN); 83% received anti-CD25. Results. 53 KTRs were included; 32% developed DSA during the 1st year after KT. Significantly lower 7-year graft survival was observed in those who developed DSA. No difference was observed in Treg numbers up to 9 months after KT, between DSA positive and negative. However, at 12 months after KT, DSA-negative patients had significantly higher numbers of Treg. Conclusions. Early development of DSA was not associated to variations in Treg abundance. The differences in Treg numbers observed at the late time point may reflect better immune acceptance of the graft and may be associated to long-term effects. Additional inhibitory mechanisms participating earlier in DSA development after KT deserve to be sought.

Recovery from ischemic acute kidney injury by spironolactone administration.

BACKGROUND: Prophylactic mineralocorticoid receptor (MR) antagonism with spironolactone (Sp) in rats completely prevents renal damage induced by ischemia. Because acute renal ischemia cannot typically be predicted, this study was designed to investigate whether Sp could prevent renal injury after an ischemic/reperfusion insult. METHODS: Six groups of male Wistar rats were studied: rats that received a sham abdominal operation (S); rats that underwent 20 min of ischemia and reperfusion for 24 h (I/R) and four groups of rats treated with Sp (20 mg/kg) 0, 3, 6 or 9 h after ischemia. RESULTS: As expected, I/R resulted in renal dysfunction characterized by a fall in renal blood flow and glomerular filtration rate and severe tubular injury which was confirmed by a significant increase in tubular damage biomarkers including kidney injury molecule-1, heat shock protein 72 and urinary protein excretion. The renal injury induced by I/R was in part due to Rho-kinase, endothelin and angiotensin II type 1 receptor upregulation. Interestingly, Sp administration at 0 and 3 h after ischemia completely reversed and prevented the damage induced by I/R. The protection induced by Sp given 6 h after ischemia was partial, but no protection was observed by administering Sp 9 h after ischemia. CONCLUSION: Our results show that MR antagonism administered, either immediately or 3 h after I/R, effectively prevented ischemic acute renal injury, indicating that spironolactone is a promising agent for preventing acute kidney injury once an ischemic insult has occurred.

[Evidence on the role of HLA and MICA antibodies in renal graft loss]. / Evidencia del impacto de los anticuerpos anti-HLA y anti-MICA en la pérdida del injerto renal.

BACKGROUND: HLA and MICA antibodies are increasingly associated with poorer graft survival. The aim of this study is to report the frequency of graft loss 2 years after the detection of HLA abs and MICA abs among a group of kidney transplant recipients. METHODS: We tested 196 patients with a functioning graft. Sera were screened for HLA and MICA IgG abs by Luminex, using the LABScreen Mixed, and LABScreen PRA. The sera were screened for MICA abs by Luminex. RESULTS: Of 196 kidney transplant recipients (mean age 36.7 years, 42% female), one hundred twenty four (63.3%) were negative to all tested abs, and 72 (36.7%) were positive for: HLA abs alone = 34, MICA abs alone = 29, and HLA+MICA abs = 9. At a median followup of 20.5 (1.2-25.2) months, 8 patients lost their grafts due to biopsy-confirmed chronic allograft injury: 2/124 (1.6%) ab-negative, and 6/72 (8.3%) ab-positive, with a significantly lower survival for the Ab-positive group (p = 0.046, log-rank test). CONCLUSIONS: The presence of circulating abs was associated with an increased risk of graft loss, and the coexistence of HLA and MICA abs increases the risk of graft loss.

Evidencia del impacto de los anticuerpos anti-HLA y anti-MICA en la pérdida del injerto renal / Evidence on the role of HLA and MICA antibodies in renal graft loss

Antecedentes: Los anticuerpos anti-HLA y anti-MICA se han asociado cada vez con mayor frecuencia a menor supervivencia del injerto renal. El objetivo de este estudio es comunicar la frecuencia de pérdida del injerto dos años después de la detección de anticuerpos anti-HLA, anti-MICA, o ambos, en un grupo de receptores de trasplante renal (RTR). Métodos: Estudiamos a 196 RTR con injerto funcional. El suero de los pacientes fue analizado para la presencia de anticuerpos IgG anti-HLA clase I y clase II con Luminex utilizando LABScreen®Mixed y LABScreen® PRA. La presencia de anticuerpos anti-MICA en el mismo suero se analizó por Luminex. Resultados: De 196 RTR (edad promedio 36.7 años, 42% sexo femenino), 124 (63.3%) fueron negativos a todos los anticuerpos estudiados y 72 (36.7%) fueron positivos: 34 para anticuerpos anti-HLA solo, 29 para anticuerpos anti-MICA solo y nueve para anticuerpos anti-HLA+anti-MICA. A una mediana de seguimiento de 20.5 meses (1.2-25.2), ocho pacientes perdieron el injerto por daño crónico del mismo, confirmado por biopsia: 2/124 (1.6%) del grupo de anticuerpos negativos y 6/72 (8.3%) del grupo de anticuerpos positivos, con una supervivencia del injerto significativamente inferior para el grupo de anticuerpos positivos (p=0.046, log-rank test). Conclusiones: La presencia de anticuerpos circulantes estuvo asociados con riesgo incrementado para pérdida del injerto; la coexistencia de anticuerpos anti-HLA y anti-MICA produjo el riesgo más alto para pérdida del injerto en la población analizada.

BACKGROUND: HLA and MICA antibodies are increasingly associated with poorer graft survival. The aim of this study is to report the frequency of graft loss 2 years after the detection of HLA abs and MICA abs among a group of kidney transplant recipients. METHODS: We tested 196 patients with a functioning graft. Sera were screened for HLA and MICA IgG abs by Luminex, using the LABScreen Mixed, and LABScreen PRA. The sera were screened for MICA abs by Luminex. RESULTS: Of 196 kidney transplant recipients (mean age 36.7 years, 42% female), one hundred twenty four (63.3%) were negative to all tested abs, and 72 (36.7%) were positive for: HLA abs alone = 34, MICA abs alone = 29, and HLA+MICA abs = 9. At a median followup of 20.5 (1.2-25.2) months, 8 patients lost their grafts due to biopsy-confirmed chronic allograft injury: 2/124 (1.6%) ab-negative, and 6/72 (8.3%) ab-positive, with a significantly lower survival for the Ab-positive group (p = 0.046, log-rank test). CONCLUSIONS: The presence of circulating abs was associated with an increased risk of graft loss, and the coexistence of HLA and MICA abs increases the risk of graft loss.

Long-term renal graft function and survival in patients with high-risk for cytomegalovirus infection receiving preemptive therapy.

BACKGROUND: Preemptive therapy reduces the risk of cytomegalovirus disease in high-risk kidney transplant patients. The advantage of this strategy is that only a fraction of patients receive antiviral drugs for a limited time, which decreases costs and toxicity but requires frequent monitoring and may not prevent complications of asymptomatic cytomegalovirus replication. MATERIAL AND METHODS: Long-term graft-function and patient survival of high-risk kidney transplant patients who received preemptive therapy guided by pp65 antigenemia was compared to those whose assay remained negative throughout the first post-transplant year. RESULTS: Between August 1997 and March 2005, 24 of 272 patients were CMV D+/R-. Thirteen of the 24 (54.2%) developed a positive CMV assay during follow-up; the time between transplant and first positive antigenemia was 66.7 +/- 58.3 days (range 29-251 days). Four patients developed symptoms associated with CMV, one of whom succumbed from complications of CMV neumonitis. Overall, no significant differences were observed in SCr, eGFR, delta SCr, and delta eGFR during a 60-month followup between patients who developed CMV infection or disease and those who remained pp65 antigenemia-negative throughout the first 12 post-transplant months. Additionally, no deaths or graft loss occurred during the long-term follow up of this cohort. CONCLUSIONS: Our results suggest that in this high risk group of kidney transplant recipients, treating CMV replication using a preemptive strategy during the first posttransplant year is associated with a low rate of CMV complications and probably interferes with the alleged long-term negative indirect effects of CMV on kidney function and survival.

HLA and MICA antibodies: further evidence of their impact on graft loss two years after their detection.

1. At the median post-transplant follow-up (to Ab evaluation) of 51.4 months, the prevalence of anti-HLA and anti-MICA Abs was 21.9% and 19%, respectively. 2. Overall, of the 196 patients included, 124 (63.3%) were negative to all tested Abs, and 72 (36.7%) were positive for: HLA Abs alone = 34; MICA Abs alone = 29; and HLA + MICAAbs = 9. 3. Two years after Ab evaluation, graft survival was significantly lower for patients with HLA + MICA Abs (p = 0.046). 4. The proportion of patients without CNI drugs at the time of Ab evaluation was greater in patients with one Ab and even greater in those with two Abs (HLA + MICA) when compared to patients with a negative Ab determination (p = 0.037).