IL-1 receptor blockade alleviates endotoxin-mediated impairment of renal drug excretory functions in rats

Divergent Actions of Renal Tubular and Endothelial Type 1 IL-1 Receptor Signaling in Toxin-Induced AKI

SIGNIFICANCE STATEMENT

Activation of the type 1 IL-1 receptor (IL-1R1) triggers a critical innate immune signaling cascade that contributes to the pathogenesis of AKI. However, blockade of IL-1 signaling in AKI has not consistently demonstrated kidney protection. The current murine experiments show that IL-1R1 activation in the proximal tubule exacerbates toxin-induced AKI and cell death through local suppression of apolipoprotein M. By contrast, IL-1R1 activation in endothelial cells ameliorates AKI by restoring VEGFA-dependent endothelial cell viability. Using this information, future delivery strategies can maximize the protective effects of blocking IL-1R1 while mitigating unwanted actions of IL-1R1 manipulation.

BACKGROUND

Activation of the type 1 IL-1 receptor (IL-1R1) triggers a critical innate immune signaling cascade that contributes to the pathogenesis of AKI. IL-1R1 is expressed on some myeloid cell populations and on multiple kidney cell lineages, including tubular and endothelial cells. Pharmacological inhibition of the IL-1R1 does not consistently protect the kidney from injury, suggesting there may be complex, cell-specific effects of IL-1R1 stimulation in AKI.

METHODS

To examine expression of IL-1 and IL-1R1 in intrinsic renal versus infiltrating immune cell populations during AKI, we analyzed single-cell RNA sequencing (scRNA-seq) data from kidney tissues of humans with AKI and mice with acute aristolochic acid exposure. We then investigated cell-specific contributions of renal IL-1R1 signaling to AKI using scRNA-seq, RNA microarray, and pharmacological interventions in mice with IL-1R1 deletion restricted to the proximal tubule or endothelium.

RESULTS

scRNA-seq analyses demonstrated robust IL-1 expression in myeloid cell populations and low-level IL-1R1 expression in kidney parenchymal cells during toxin-induced AKI. Our genetic studies showed that IL-1R1 activation in the proximal tubule exacerbated toxin-induced AKI and cell death through local suppression of apolipoprotein M. By contrast, IL-1R1 activation in endothelial cells ameliorated aristolochic acid-induced AKI by restoring VEGFA-dependent endothelial cell viability and density.

CONCLUSIONS

These data highlight opposing cell-specific effects of IL-1 receptor signaling on AKI after toxin exposure. Disrupting pathways activated by IL-1R1 in the tubule, while preserving those triggered by IL-1R1 activation on endothelial cells, may afford renoprotection exceeding that of global IL-1R1 inhibition while mitigating unwanted actions of IL-1R1 blockade.

Inflammation Induces Changes in the Functional Expression of P-gp, BCRP, and MRP2: An Overview of Different Models and Consequences for Drug Disposition

The ATP-binding cassette (ABC) transporters play a key role in drug pharmacokinetics. These membrane transporters expressed within physiological barriers can be a source of pharmacokinetic variability. Changes in ABC transporter expression and functionality may consequently affect the disposition of substrate drugs, resulting in different drug exposure. Inflammation, present in several acute and chronic diseases, has been identified as a source of modulation in drug transporter expression leading to variability in drug response. Its regulation may be particularly dangerous for drugs with a narrow therapeutic index. In this context, numerous in vitro and in vivo models have shown up- or downregulation in the expression and functionality of ABC transporters under inflammatory conditions. Nevertheless, the existence of contradictory data and the lack of standardization for the models used have led to a less conclusive interpretation of these data.

Evaluation of Neutrophil Gelatinase-Associated Lipocalin as a Predictor of Glomerular Filtration Rate and Amikacin Clearance During Early Rat Endotoxemia: Comparison with Traditional Endogenous and Exogenous Biomarkers

BACKGROUND AND OBJECTIVES

Renal elimination of amikacin and other aminoglycosides is slowed down in sepsis-induced acute kidney injury increasing the risk of adverse effects. Since neutrophil gelatinase-associated lipocalin (NGAL) and aminoglycosides share the mechanisms for renal excretion, the predictive power of NGAL was examined towards the changes in amikacin pharmacokinetics during early endotoxemia in anesthetized Wistar rats.

METHODS

Endogenous biomarkers of inflammation and acute kidney injury were assessed including NGAL in saline-injected controls and two groups of rats challenged with an intravenous injection of bacterial lipopolysaccharide (5 mg/kg)-a fluid-resuscitated group (LPS) and a fluid-resuscitated group infused intravenously with 8 μg/kg/h terlipressin (LPS-T). Sinistrin and amikacin were infused to measure glomerular filtration rate (GFR) and amikacin clearance (CL_am). The investigations included blood gas analysis, chemistry and hematology tests and assessment of urine output, creatinine clearance (CL_cr) and sinistrin clearance (CL_sini).

RESULTS

Within 3 h of injection, systemic and renal inflammatory responses were induced by lipopolysaccharide. Gene and protein expression of NGAL was increased in the kidneys and the concentrations of NGAL in the plasma (pNGAL) and urine rose 4- to 38-fold (P < 0.01). The decreases in CL_am and the GFR markers (CL_cr, CL_sini) were proportional, reflecting the extent to which endotoxemia impaired the major elimination mechanism for the drug. Terlipressin attenuated lipopolysaccharide-induced renal dysfunction (urine output, CL_cr, CL_sini) and accelerated CL_am. The pNGAL showed a strong association with the CL_sini (rs = - 0.77, P < 0.0005). Concerning prediction of CL_am, pNGAL was comparable to CL_cr (mean error - 24%) and inferior to CL_sini (mean error - 6.4%), while the measurement of NGAL in urine gave unsatisfactory results.

CONCLUSIONS

During early endotoxemia in the rat, pNGAL has a moderate predictive ability towards CL_am. Clinical studies should verify whether pNGAL can support individualized dosing of aminoglycosides to septic patients.

Interleukin 1 receptor (IL-1R1) activation exacerbates toxin-induced acute kidney injury

Acute kidney injury (AKI) is a leading cause of morbidity and mortality. Drug-induced/toxic AKI can be caused by a number of therapeutic agents. Cisplatin is an effective chemotherapeutic agent whose administration is limited by significant nephrotoxicity. Therapies to prevent cisplatin-induced AKI are lacking. Although tumor necrosis factor-α (TNF) plays a key role in the pathogenesis of cisplatin nephrotoxicity, the innate immune signaling pathways that trigger TNF generation in this context require elucidation. In this regard, sterile injury triggers the release and activation of both isoforms of interleukin(IL)-1, IL-1α and IL-1β. In turn, stimulation of the interleukin-1 receptor (IL-1R1) by these ligands engages a proinflammatory signaling cascade that induces TNF induction. We therefore hypothesized that IL-1R1 activation exacerbates cisplatin-induced AKI by inducing TNF production, thereby augmenting inflammatory signals between kidney parenchymal cells and infiltrating myeloid cells. IL-1R1+/+ (WT) and IL-1R1-/- (KO) mice were subjected to cisplatin-induced AKI. Compared with WT mice, IL-1R1 KO mice had attenuated AKI as measured by serum creatinine and BUN, renal NGAL mRNA levels, and blinded histological analysis of kidney pathology. In the cisplatin-injured kidney, IL-1R1 KO mice had diminished levels of whole kidney TNF, and fewer Ly6G-expressing neutrophils. In addition, an unbiased machine learning analysis of intrarenal immune cells revealed a diminished number of CD11bint/CD11cint myeloid cells in IL-1R1 KO injured kidneys compared with IL-1R1 WT kidneys. Following cisplatin, IL-1R1 KO kidneys, compared with WTs, had fewer TNF-producing: macrophages, CD11bint/CD11cint cells, and neutrophils, consistent with an effect of IL-1R1 to polarize intrarenal myeloid cells toward a proinflammatory phenotype. Interruption of IL-1-dependent signaling pathways warrants further evaluation to decrease nephrotoxicity during cisplatin therapy.

Mild intracellular acidification by dexamethasone attenuates mitochondrial dysfunction in a human inflammatory proximal tubule epithelial cell model

Septic acute kidney injury (AKI) associates with poor survival rates and often requires renal replacement therapy. Glucocorticoids may pose renal protective effects in sepsis via stimulation of mitochondrial function. Therefore, we studied the mitochondrial effects of dexamethasone in an experimental inflammatory proximal tubule epithelial cell model. Treatment of human proximal tubule epithelial cells with lipopolysaccharide (LPS) closely resembles pathophysiological processes during endotoxaemia, and led to increased cytokine excretion rates and cellular reactive oxygen species levels, combined with a reduced mitochondrial membrane potential and respiratory capacity. These effects were attenuated by dexamethasone. Dexamethasone specifically increased the expression and activity of mitochondrial complex V (CV), which could not be explained by an increase in mitochondrial mass. Finally, we demonstrated that dexamethasone acidified the intracellular milieu and consequently reversed LPS-induced alkalisation, leading to restoration of the mitochondrial function. This acidification also provides an explanation for the increase in CV expression, which is expected to compensate for the inhibitory effect of the acidified environment on this complex. Besides the mechanistic insights into the beneficial effects of dexamethasone during renal cellular inflammation, our work also supports a key role for mitochondria in this process and, hence, provides novel therapeutic avenues for the treatment of AKI.

Pharmacokinetics of Boldine in Control and Mrp2-Deficient Rats

The aim of the present study was to describe the currently poorly understood pharmacokinetics (PK) of boldine in control rats (LW, Lewis rats), and Mrp2 transporter-deficient rats (TR-). Animals from the LW and TR- groups underwent a bolus dose study with 10 mg/kg of boldine applied either orally or intravenously in order to evaluate the major PK parameters. The TR- rats demonstrated significantly reduced total clearance with prolonged biological half-life (LW 12±4.6 versus TR- 20±4.4 min), decreased volume of distribution (LW 3.2±0.4 l/kg versus TR- 2.4±0.4 l/kg) and reduced bioavailability (LW 7 % versus TR- 4.5 %). Another set of LW and TR- rats were used for a clearance study with continuous intravenous administration of boldine. The LW rats showed that biliary and renal clearance formed less than 2 % of the total clearance of boldine. The treatment of samples with β glucuronidase showed at least a 38 % contribution of conjugation reactions to the overall clearance of boldine. The TR- rats demonstrated reduced biliary clearance of boldine and its conjugates, which was partly compensated by their increased renal clearance. In conclusion, this study presents the PK parameters of boldine and shows the importance of the Mrp2 transporter and conjugation reactions in the elimination of the compound.

Long-term administration of advanced glycation end-product stimulates the activation of NLRP3 inflammasome and sparking the development of renal injury

The accumulation of advanced glycation end-products (AGEs) and the enhanced interaction of AGE with their cellular receptor (RAGE) have been implicated in the progression of chronic kidney disease. The purpose of this study was to examine whether the AGE/RAGE-induced nephrotoxic effects are associated with inflammasome activation and endothelial dysfunction. Chronic renal injury was examined in BALB/c mice by the long-term administration of carbonyl-AGE for 16 weeks. Endothelial dysfunction was detected by measuring the number of circulating endothelial progenitor cells (EPCs) and the levels of nitric oxide synthase (eNOS) and nitric oxide (NO) in kidneys. Results showed that administration of methylglyoxal-bovine serum albumin (MG-BSA) AGE accelerated renal MG, carboxyethyl lysine, carboxymethyl lysine and malondialdehyde formation and, in parallel, the levels of serum creatinine and blood urea nitrogen (BUN) were significantly increased. Expression of RAGE and NLRP3 inflammasome-related proteins (TXNIP, NLRP3, procaspase-1 and caspase-1) and IL (interleukin)-1β secretion were upregulated, whereas the levels of EPCs, eNOS and NO were lower in MG-BSA-treated mice. This induction by MG-BSA was significantly inhibited by RAGE antagonist. Our results firstly reveal a possible mechanism of AGE-mediated renal dysfunction upon NLRP3 inflammasome activation. Therapeutic blockade of RAGE may ameliorate renal and endothelial functions in subjects under high AGE burden.

The neutrophil elastase inhibitor, sivelestat, attenuates sepsis-related kidney injury in rats

Sepsis-induced acute kidney injury (AKI) represents a major cause of mortality in intensive care units. Sivelestat, a selective inhibitor of neutrophil elastase (NE), can attenuate sepsis-related acute lung injury. However, whether sivelestat can preserve kidney function during sepsis remains unclear. In this study, we thus examined the effects of sivelestat on sepsis-related AKI. Cecal ligation and puncture (CLP) was performed to induce multiple bacterial infection in male Sprague-Dawley rats, and subsequently, 50 or 100 mg/kg sivelestat were administered by intraperitoneal injection immediately after the surgical procedure. In the untreated rats with sepsis, the mean arterial pressure (MAP) and glomerular filtration rate (GFR) were decreased, whereas serum blood urea nitrogen (BUN) and neutrophil gelatinase-associated lipocalin (NGAL) levels were increased. We found that sivelestat promoted the survival of the rats with sepsis, restored the impairment of MAP and GFR, and inhibited the increased BUN and NGAL levels; specifically, the higher dose was more effective. In addition, sivelestat suppressed the CLP-induced macrophage infiltration, the overproduction of pro-inflammatory mediators (tumor necrosis factor-α, interleukin-1β, high-mobility group box 1 and inducible nitric oxide synthase) and serine/threonine kinase (Akt) pathway activation in the rats. Collectively, our data suggest that the inhibition of NE activity with the inhibitor, sivelestat, is beneficial in ameliorating sepsis-related kidney injury.