Effect of remote ischemic conditioning on dendritic cell number in blood after renal transplantation — flow cytometry in a porcine model

Subclinical effects of remote ischaemic conditioning in human kidney transplants revealed by quantitative proteomics

Background

Remote ischaemic conditioning (RIC) is currently being explored as a non-invasive method to attenuate ischaemia/reperfusion injuries in organs. A randomised clinical study (CONTEXT) evaluated the effects of RIC compared to non-RIC controls in human kidney transplants.

Methods

RIC was induced prior to kidney reperfusion by episodes of obstruction to arterial flow in the leg opposite the transplant using a tourniquet (4 × 5 min). Although RIC did not lead to clinical improvement of transplant outcomes, we explored whether RIC induced molecular changes through precision analysis of CONTEXT recipient plasma and kidney tissue samples by high-resolution tandem mass spectrometry (MS/MS).

Results

We observed an accumulation of muscle derived proteins and altered amino acid metabolism in kidney tissue proteomes, likely provoked by RIC, which was not reflected in plasma. In addition, MS/MS analysis demonstrated transient upregulation of several acute phase response proteins (SAA1, SAA2, CRP) in plasma, 1 and 5 days post-transplant in RIC and non-RIC conditions with a variable effect on the magnitude of acute inflammation.

Conclusions

Together, our results indicate sub-clinical systemic and organ-localised effects of RIC.

Remote ischemic preconditioning of transplant recipients to reduce graft ischemia and reperfusion injuries: A systematic review

BACKGROUND

Solid organ transplantation is an accepted treatment for end-stage solid organ diseases. During the procedure, ischemia and reperfusion injury may affect graft and patient outcomes. Remote ischemic preconditioning (rIC) has been shown to reduce ischemia and reperfusion injury and can be performed safely. Thus, rIC may potentially improve outcomes after solid organ transplantation. Traditionally, the focus of rIC has been on the donor. However, preconditioning the recipient may be a more suitable approach in transplant settings. The current review analyzed previously published studies where rIC was performed on transplant recipients.

METHODS

PubMed and EMBASE databases were searched for eligible clinical and animal studies evaluating rIC of recipients. Articles were analyzed and compared qualitatively. Risk of bias was assessed using the Cochrane Collaboration's tool for interventional clinical studies and SYRCLEs risk of bias tool for animal studies.

RESULTS

A total of 12 studies were included. Overall, these studies were heterogeneous due to differences in populations and intervention set-up. Some of the studies suggested improvement of graft function, while other studies did not show any effect. The quality of the 12 included studies was predominantly low.

CONCLUSION

Due to the heterogeneity and quality of the included studies the result, that rIC may be beneficial in transplantation of some organs, should be interpreted with caution. The result must be confirmed by further clinical studies.

The Effect of Deoxynivalenol on Selected Populations of Immunocompetent Cells in Porcine Blood-A Preliminary Study

Deoxynivalenol (DON) is one of the most prevalent mycotoxins in Europe. Pigs are an animal species that is most susceptible to this mycotoxin. Deoxynivalenol causes significant losses in pig production by lowering feed intake, decreasing daily weight gains, disrupting immune responses, and increasing susceptibility to diseases. The aim of this experiment was to determine the influence of feed contaminated with DON at concentrations insignificantly higher than recommended by the European Commission (900 µg/kg). The experimental feed contained 1008 μg DON/kg. The experiment was performed on eight weaners from the same litter. The animals were randomly divided into two groups: an experimental group (M, n = 4) fed contaminated feed and a control group (C, n = 4) administered feed free of mycotoxins. The experiment lasted for six weeks, and peripheral blood samples were collected from the animals for analyses of selected morphological parameters and changes in the percentages of CD4⁺8-, CD4-8⁺, and CD4⁺8⁺ lymphocytes and antigen-presenting cells (APC) with CD14⁺172⁺ (monocytes), CD172ahigh4-14- (conventional dendritic cells, cDC), and CD172adim4⁺14- (plasmacytoid dendritic cells, pDC) phenotypes. The morphological parameters of porcine blood samples were determined by flow cytometry with non-fluorescent particle-size calibration standards, and no differences were observed between groups M and C. An immunophenotyping analysis of lymphocytes and dendritic cells (DC) revealed an increase in the percentage of CD4⁺8-, CD172ahigh4-14-, and CD172adim4⁺14- cells, and a decrease in the number of CD4-8⁺ cells in group M. The results of this experiment suggest that prolonged exposure to low doses of DON can change the proportions of immunocompetent cells (a shift towards humoral immunity), without affecting their overall counts.

Molecular Mechanisms of Renal Ischemic Conditioning Strategies

Ischemia-reperfusion injury is the leading cause of acute kidney injury in a variety of clinical settings such as renal transplantation and hypovolemic and/or septic shock. Strategies to reduce ischemia-reperfusion injury are obviously clinically relevant. Ischemic conditioning is an inherent part of the renal defense mechanism against ischemia and can be triggered by short periods of intermittent ischemia and reperfusion. Understanding the signaling transduction pathways of renal ischemic conditioning can promote further clinical translation and pharmacological advancements in this era. This review summarizes research on the molecular mechanisms underlying both local and remote ischemic pre-, per- and postconditioning of the kidney. The different types of conditioning strategies in the kidney recruit similar powerful pro-survival mechanisms. Likewise, renal ischemic conditioning mobilizes many of the same protective signaling pathways as in other organs, but differences are recognized.

The effect of remote ischemic postconditioning on graft function in patients undergoing living donor kidney transplantation

BACKGROUND

We evaluated whether remote ischemic postconditioning (RiPoC) could improve initial graft function in living donor kidney transplantation (KT).

METHODS

Patients undergoing living donor KT were randomly assigned to either RiPoC (n=30) or control group (n=30). Immediately after reperfusion in the RiPoC group, three cycles of ischemia and reperfusion, lasting 5 min each, were performed on one upper limb. Renal function was assessed before surgery, 2 hr after surgery, and at 12-hr intervals for 96 hr postsurgery by measuring serum creatinine (sCr) and the estimated glomerular filtration rate (eGFR). Urine output and urine creatinine were assessed until postoperative day 7, and hospital stay and complication rates were compared.

RESULTS

The time for sCr to reach 50% of its preoperative level was significantly shorter in the RiPoC group than in the control group [12 (12-24) hr for RiPoC vs. 24 (21-36) hr for the control, P=0.005]. The number of patients whose sCr was reduced by 50% within 24 hr was significantly greater in the RiPoC group than in the control group [n=26 (87%) in RiPoC vs. n=18 (60%) in control, P=0.020]. However, there were no differences in sCr and eGFR thereafter, the incidence of graft dysfunction or complication rates between groups.

CONCLUSION

In this study, RiPoC appeared to hasten the recovery of graft function within 24 hr but did not affect the graft function thereafter. However, considering most recipients had immediate graft function, further studies with deceased donors or studies powered to detect a smaller difference are needed.

Protective effects of three remote ischemic conditioning procedures against renal ischemic/reperfusion injury in rat kidneys: a comparative study

BACKGROUND

Remote ischemic perconditioning (RIPerC), remote ischemic postconditioning (RIPostC), and remote ischemic perconditioning + postconditioning (RIPerC + RIPostC) protect against renal ischemia reperfusion injury (IRI). However, the most beneficial approach among these is not known.

AIMS

To compare the protective effects and study the mechanisms of three different remote ischemic conditioning in preventing IRI in the rat kidney.

METHODS

Fifty healthy adult male Sprague-Dawley rats were randomly assigned to five groups: sham, IRI, RIPerC, RIPostC, and RIPerC + RIPostC. Right nephrectomy was performed initially in all rats. IRI was induced by occluding the left renal artery for 60 min, followed by reperfusion for 24 h. RIPerC, RIPostC, and RIPerC + RIPostC were induced with 5-min ischemia/reperfusion (I/R) cycles using a tourniquet on the right hind limb.

RESULTS

The IRI group showed significant serologic evidence of renal injury compared to the sham group (P < 0.05). The RIPerC, RIPostC, and RIperC + RIpostC groups displayed significantly lower levels of renal dysfunction than the IRI group (P < 0.05). Superoxide dismutase (SOD) levels were significantly lower in the IRI group than in the sham group (P = 0.003), but were significantly less depressed in the RIPerC, RIPostC, and RIperC + RIpostC groups (P < 0.05). The IRI group displayed more severe renal tubular injury than the RIPerC, RIPostC, and RIPerC + RIPostC groups (P < 0.05).

CONCLUSION

All three remote ischemic conditioning showed similar therapeutic potential for preventing renal IRI. The RIPerC + RIPostC protocol did not show an additive effect from the combination of preconditioning and postconditioning. The protective mechanism may be due to the stimulation of endogenous antioxidant activity by transient limb ischemia-reperfusion.

Effect of remote ischemic postconditioning on patients undergoing living donor liver transplantation

The aim of this study was to evaluate the protective effect of remote ischemic postconditioning (RIPostC) on graft function and acute kidney injury (AKI) after living donor liver transplantation (LT). Recipients undergoing elective living donor LT were randomly assigned to either the RIPostC group or the control group. Immediately after reperfusion, 4 cycles of ischemia and reperfusion lasting for 5 minutes each were performed on 1 upper limb in the RIPostC group. Graft function was assessed through evaluations of the serum levels of total bilirubin and liver enzymes and the prothrombin time for 28 days after surgery. The incidence of AKI, as defined by the Risk, Injury, Failure, Loss, and End-Stage Kidney Disease classification, was evaluated within 28 days of the operation. In addition, the incidences of graft dysfunction, acute cellular rejection, and major complications; the 1-, 3-, and 6-month mortality rates; the length of stay in the intensive care unit; and the length of hospital stay were also investigated. In all, 78 patients were enrolled in the analysis (n = 39 in each group). No differences in graft function or clinical outcomes were observed between the groups. The incidences of postoperative AKI were 38% (n = 15) in the RIPostC group and 72% (n = 28) in the control group (P = 0.006). Despite no improvements in postoperative graft function, RIPostC decreased the incidence of postoperative AKI after living donor LT in this study. However, no other clinical benefits with respect to the complication rate, length of hospital stay, or short-term mortality rate were observed. Thus, further studies will be needed to evaluate the clinical efficacy of RIPostC in LT fully.

Involvement of Caveolin-1 in CD83 Internalization in Mouse Dendritic Cells

To become potent T-cell stimulators, DCs need to mature. Treatment with soluble CD83 (sCD83) induces immune tolerance and protects against transplant rejection by maintaining dendritic cells in an immature, tolerogenic state. Until now, the mechanism through which sCD83 keeps DCs immature has not been investigated. The internalizing pathway of CD83 was screened by Western blot, and the direct interactions between internalized proteins were verified through coimmunoprecipitation (co-IP) and transmission electron microscopy (TEM). CD83 plasma membrane levels were detected by Western blot using a plasma membrane protein extraction protocol. The changes in CD83 surface levels in DCs were detected by flow cytometry. Caveolin-1 function was detected in a kidney transplant model. In this study, we demonstrated that caveolin-1 could affect CD83 level during endocytosis in mouse DCs. Caveolin-1 coprecipitates with CD83, as demonstrated by co-IP analysis. TEM morphometric analysis of the entire CD83 distribution associated with internalized caveolin-1 demonstrated a significant interaction in cellular vesicles. sCD83 reduces endogenous CD83 plasma membrane levels, and caveolin-1 knockdown reverts CD83 levels in plasma membrane. sCD83 treatment decreases CD83 surface levels in DCs. siRNA to caveolin-1 in DCs inhibits this effect of sCD83. The effects of sCD83-treated DCs were proved in CD1 mice. Knocking down caveolin-1 in DCs obstructs the effects of sCD83 on kidney transplant. In conclusion, our data indicated that a caveolin-dependent endocytic pathway is involved in CD83 internalization in DCs and that caveolin-1 is involved in the activity of DCs.