Ischaemic and inflammatory injury in renal graft from brain death donation: an update review

Isoflurane preconditioning protects against renal ischemia/reperfusion injury in diabetes via activation of the Brg1/Nrf2/HO-1 signaling pathway

PURPOSE

To examine whether isoflurane preconditioning (IsoP) has a protective effect against renal ischemia/reperfusion injury (I/RI) in diabetic conditions and to further clarify the underlying mechanisms.

METHODS

Control and streptozotocin-induced diabetic rats were randomly assigned to five groups, as follows: normal sham, normal I/R, diabetic sham, diabetic I/R, and diabetic I/R + isoflurane. Renal I/RI was induced by clamping renal pedicle for 45 min followed by reperfusion for 24 h. IsoP was achieved by exposing the rats to 2% isoflurane for 30 min before vascular occlusion. Kidneys and blood were collected after reperfusion for further analysis. Renal histology, blood urea nitrogen, serum creatinine, oxidative stress, inflammatory cytokines, and renal cell apoptosis were assessed. Furthermore, the expression of brahma related gene 1 (Brg1), nuclear factor-erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and nuclear factor-κB (NF-κB) were determined.

RESULTS

Compared with control, diabetic rats undergoing I/R presented more severe renal injury, oxidative stress, inflammatory reaction, and apoptosis with the impairment of Brg1/Nrf2/HO-1 signaling. All these alterations were significantly attenuated by pretreatment with isoflurane.

CONCLUSIONS

These findings suggest that isoflurane could alleviate renal I/RI in diabetes, possibly through improving Brg1/Nrf2/HO-1 signaling.

Toll-like Receptor 4 in Acute Kidney Injury

Acute kidney injury (AKI) is a common and devastating pathologic condition, associated with considerable high morbidity and mortality. Although significant breakthroughs have been made in recent years, to this day no effective pharmacological therapies for its treatment exist. AKI is known to be connected with intrarenal and systemic inflammation. The innate immune system plays an important role as the first defense response mechanism to tissue injury. Toll-like receptor 4 (TLR4) is a well-characterized pattern recognition receptor, and increasing evidence has shown that TLR4 mediated inflammatory response, plays a pivotal role in the pathogenesis of acute kidney injury. Pathogen-associated molecular patterns (PAMPS), which are the conserved microbial motifs, are sensed by these receptors. Endogenous molecules generated during tissue injury, and labeled as damage-associated molecular pattern molecules (DAMPs), also activate pattern recognition receptors, thereby offering an understanding of sterile types of inflammation. Excessive, uncontrolled and/or sustained activation of TLR4, may lead to a chronic inflammatory state. In this review we describe the role of TLR4, its endogenous ligands and activation in the inflammatory response to ischemic/reperfusion-induced AKI and sepsis-associated AKI. The potential regeneration signaling patterns of TLR4 in acute kidney injury, are also discussed.

Dynamic changes of neutrophil-to-lymphocyte ratio in brain-dead donors and delayed graft function in kidney transplant recipients

Objectives

Neutrophil-to-lymphocyte ratio (NLR) is a simple parameter implying the inflammatory status. We aimed to explore the association of brain-dead donor NLR change with delayed graft function (DGF) in kidney transplant recipients.

Methods

We retrospectively analyzed the data on 102 adult brain-dead donors and their corresponding 199 kidney transplant recipients (2018 − 2021). We calculated ΔNLR by subtracting the NLR before evaluating brain death from the preoperative NLR. Increasing donor NLR was defined as ΔNLR > 0.

Results

Forty-four (22%) recipients developed DGF after transplantation. Increasing donor NLR was significantly associated with the development of DGF in recipients (OR 2.8, 95% CI 1.2 − 6.6; p = .018), and remained significant (OR 2.6, 95% CI 1.0 − 6.4; p = .040) after adjustment of confounders including BMI, hypertension, diabetes, and the occurrence of cardiac arrest. When acute kidney injury (AKI) was included in the multivariable analysis, increasing donor NLR lost its independent correlation with DGF, while AKI remained an independent risk factor of recipient DGF (OR 4.5, 95% CI 2.7 − 7.6; p < .001). The area under the curve of combined increasing NLR and AKI in donors (0.873) for predicting DGF was superior to increasing donor NLR (0.625, p = .015) and AKI alone (0.859, p < .001).

Conclusions

Dynamic changes of donor NLR are promising in predicting post-transplant DGF. It will assist clinicians in the early recognition and management of renal graft dysfunction. Validation of this new biomarker in a large study is needed.

Conivaptan and Boric Acid Treatments in Acute Kidney Injury: Is This Combination Effective and Safe?

Acute kidney injury is still a worldwide clinic problem that affects kidney function and associated with high mortality risk. Unfortunately, approximately 1.7 million people are thought to die from acute kidney injury each year. Boron element is defined as an "essential trace element" for plants and thought to have a widespread role in living organisms. Boric acid, which is one of the important forms of boron, has been extensively discussed for both medicinal and nonmedicinal purposes. However, there is a lack of data in the literature to examine the relationship between boric acid and antidiuretic hormone (ADH) antagonism in kidney injury. Thus, we aimed to investigate the effects of conivaptan as an ADH antagonist and boric acid as an antioxidant agent on the post-ischemic renal injury process. In this study, the unilateral ischemia-reperfusion (I/R) injury rat model with contralateral nephrectomy was performed and blood/kidney tissue samples were taken at 6th hours of reperfusion. The effects of 10 mg/mL/kg conivaptan and 50 mg/kg boric acid were examined with the help of some biochemical and histological analyses. We observed that conivaptan generally alleviated the destructive effects of I/R and has therapeutic effects. Also of note is that conivaptan and boric acid combination tended to show negative effects on kidney function, considering the highest BUN (78.46 ± 3.88 mg/dL) and creatinine levels (1.561 ± 0.1018 mg/dL), suggesting possibly drug-drug interaction. Although it has reported that conivaptan can interact with other active substances, no experimental/clinical data on the possible interaction with boric acid have reported so far.

Prospective comparative study of postoperative systemic inflammatory syndrome in robot-assisted vs. open kidney transplantation

PURPOSE

Robot-assisted kidney transplant (RAKT) recently proved to provide functional results similar to the preferred open kidney transplant (OKT), but with inferior wound morbidity. In a comparative prospective study, we explored the systemic inflammatory response syndrome (SIRS) after KT and compared OKT with RAKT.

METHODS

Forty-nine patients underwent pre-emptive ABO-compatible kidney transplantations (KT) between January 2017 and December 2018 in 2 centers: 25 RAKT, 24 OKT. Postoperative SIRS was biologically assessed by serum markers (NGAL, CRP and IL-6) measured at: T0 (preoperative/baseline), T1(H1), T2(H6), T3(H12), T4(H24), T5(D2), T6(D3) and T7(D5) after KT.

RESULTS

Inflammatory markers + eGFR were assessed in OKT vs. RAKT. IL-6 peak value occurred at H6 and reached ×9 from baseline. CRP peak occurred at H24 and reached ×28 from baseline (All P < 0.05). NGAL decreased after surgery with a plateau (divided by 2 from baseline) from H12 to D5. There was no significant difference in IL-6, CRP and NGAL kinetics and peak values between RAKT and OKT (All P > 0.05). Serum creatinine and eGFR on postoperative days 1, 3 and 7 were similar in RAKT and OKT (All P > 0.05). Delayed graft function was not observed.

CONCLUSION

In this exploratory study, the biological evaluation of postoperative SIRS after living-donor kidney transplant revealed no significant difference between OKT and RAKT and similar functional outcomes in the short term. These results highlight the safety of RAKT as an alternative to OKT in this setting.

Safety and effectiveness of kidney transplantation using a donation after brain death donor with acute kidney injury: a retrospective cohort study

The use of kidneys from donation after brain death (DBD) donors with acute kidney injury (AKI) is a strategy to expand the donor pool. The aim of this study was to evaluate how kidney transplantation (KT) from a donor with AKI affects long-term graft survival in various situations. All patients who underwent KT from DBD donors between June 2003 and April 2016 were retrospectively reviewed. The KDIGO (Kidney Disease: Improving Global Outcomes) criteria were used to classify donor AKI. The cohort included 376 donors (no AKI group, n = 117 [31.1%]; AKI group n = 259 [68.9%]). Death-censored graft survival was similar according to the presence of AKI, AKI severity, and the AKI trend (p = 0.929, p = 0.077, and p = 0.658, respectively). Patients whose donors had AKI who received using low dose (1.5 mg/kg for three days) rabbit anti-thymocyte globulin (r-ATG) as the induction agent had significantly superior death-censored graft survival compared with patients in that group who received basiliximab (p = 0.039). AKI in DBD donors did not affect long-term death-censored graft survival. Low-dose r-ATG may be considered as an induction immunosuppression in recipients receiving kidneys with AKI because it showed better graft survival than basiliximab.

[Procurement of abdominal organs]

Solid organ transplantation is frequently carried out in this society. Under these circumstances the basic principles are altruistic organ donation and abidance by the law, which are regulated by the German Transplantation Act and by directives of the Federal Medical Council from which process instructions of the German Organ Transplantation Foundation are derived. The organ allocation is carried out by the Eurotransplant International Foundation (ET) located in Leiden, the Netherlands. Organ procurement is an essential component of the process of organ donation. This article highlights the procedure for harvesting of abdominal organs and also nonsurgical issues in the process of organ donation.

Diabetes aggravates renal ischemia and reperfusion injury in rats by exacerbating oxidative stress, inflammation, and apoptosis

Diabetic patients are more susceptible to renal ischemia/reperfusion (I/R) injury (RI/RI) and have a poor prognosis, but the underlying mechanism remains unclear. The present study aimed to examine whether diabetes could worsen acute kidney injury induced by I/R in rats and clarify its mechanism. Control and streptozotocin-induced diabetic rats were subjected to 45 min renal pedicle occlusion followed by 24 h reperfusion. Tert-butylhydroquinone (TBHQ, 16.7 mg/kg) was administrated intraperitoneally 3 times at intervals of 8 h before ischemia. Serum and kidneys were harvested after reperfusion to evaluate renal function and histological injury. Enzyme-linked immunosorbent assays were used to test pro-inflammatory cytokines. Terminal deoxynucleotidyl-transferase-mediated dUTP nick-end labeling assays were used to detect apoptotic cells, and western blotting was performed to determine the expression of B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), and cleaved caspase-3, as well as oxidative stress and inflammation-related proteins, such as nuclear factor-erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), Toll-like receptor 4 (TLR4), and nuclear factor-κB (NF-κB). Compared with control animals, diabetic rats undergoing I/R exhibited more severe tubular damage and renal dysfunction. Diabetes exacerbated oxidative stress, the inflammatory response, and apoptosis after renal I/R by enhancing TLR4/NF-κB signaling and blocking the Nrf2/HO-1 pathway. RI/RI in diabetic rats was attenuated by pretreatment with TBHQ (a Nrf2 agonist), which exerted anti-inflammatory and anti-apoptotic properties by inhibiting NF-κB signaling. These findings indicate that hyperglycemia exacerbates RI/RI by intensifying oxidative stress, inflammation, and apoptosis. Antioxidant pretreatment may alleviate RI/RI in diabetic patients.

Mesenchymal Stromal Cells for Transplant Tolerance

In solid organ transplantation lifelong immunosuppression exposes transplant recipients to life-threatening complications, such as infections and malignancies, and to severe side effects. Cellular therapy with mesenchymal stromal cells (MSC) has recently emerged as a promising strategy to regulate anti-donor immune responses, allowing immunosuppressive drug minimization and tolerance induction. In this review we summarize preclinical data on MSC in solid organ transplant models, focusing on potential mechanisms of action of MSC, including down-regulation of effector T-cell response and activation of regulatory pathways. We will also provide an overview of available data on safety and feasibility of MSC therapy in solid organ transplant patients, highlighting the issues that still need to be addressed before establishing MSC as a safe and effective tolerogenic cell therapy in transplantation.

Downregulation of endothelin A receptor (ETaR) ameliorates renal ischemia reperfusion injury by increasing nitric oxide production

AIMS

To investigate the protective effects of downregulating ETaR expression on renal ischemia reperfusion injury (IRI).

MAIN METHODS

The renal IRI model was generated by clamping the left renal artery for 60 min followed by nephrectomy of the right kidney. ETaR siRNA were perfused through the renal artery during ischemia. HE staining was performed to assess histological injury. PCR was performed to determine the expression of NF-κb, TNF-α, IFN-γ, IL-6 and TGF-β. ELISA was used to determine the levels of ET-1, TGF-β and eNOS. The level of nitric oxide (NO) was tested by the NO detection kit. The expression of PI3K, Akt, sGC and PKG were evaluated by western blot.

KEY FINDINGS

ETaR siRNA treatment reduced the levels of serum creatinine and urea nitrogen, decreased the number of apoptotic cells, and ameliorated histological damage after IRI. PCR results demonstrated that IRI increased mRNA levels of inflammatory factors, which were inhibited by ETaR siRNA treatment. ELISA result showed that ETaR siRNA decreased the levels of ET-1, TGF-β and eNOS in the renal tissues after IRI. Western blot results demonstrated that ETaR siRNA activated the PI3K/Akt and sGC/PKG signaling pathway. Conversely, the NOS inhibitor, L-NAME, reversed the effects of ETaR siRNA treatment.

SIGNIFICANCE

ETaR siRNA treatment inhibited inflammatory response and improved renal function after renal IRI. The underlying mechanisms of ETaR siRNA treatment may be through increasing eNOS activity through PI3K/Akt signaling, which subsequently increased NO production. The increased NO reduces the expression of ET-1 by inhibiting transcription of ET-1-associated genes via the sGC/PKG signaling pathway.

C1-Inhibitor Treatment Decreases Renal Injury in an Established Brain-Dead Rat Model

BACKGROUND

Kidneys derived from brain-dead (BD) donors have lower graft survival rates compared with kidneys from living donors. Complement activation plays an important role in brain death. The aim of our study was therefore to investigate the effect of C1-inhibitor (C1-INH) on BD-induced renal injury.

METHODS

Brain death was induced in rats by inflating a subdurally placed balloon catheter. Thirty minutes after BD, rats were treated with saline, low-dose or high-dose C1-INH. Sham-operated rats served as controls. After 4 hours of brain death, renal function, injury, inflammation, and complement activation were assessed.

RESULTS

High-dose C1-INH treatment of BD donors resulted in significantly lower renal gene expression and serum levels of IL-6. Treatment with C1-INH also improved renal function and reduced renal injury, reflected by the significantly lower kidney injury marker 1 gene expression and lower serum levels of lactate dehydrogenase and creatinine. Furthermore, C1-INH effectively reduced complement activation by brain death and significantly increased functional levels. However, C1-INH treatment did not prevent renal cellular influx.

CONCLUSIONS

Targeting complement activation after the induction of brain death reduced renal inflammation and improved renal function before transplantation. Therefore, strategies targeting complement activation in human BD donors might clinically improve donor organ viability and renal allograft survival.