Indoxyl Sulfate as a Mediator Involved in Dysregulation of Pulmonary Aquaporin-5 in Acute Lung Injury Caused by Acute Kidney Injury

High mortality of acute kidney injury (AKI) is associated with acute lung injury (ALI), which is a typical complication of AKI. Although it is suggested that dysregulation of lung salt and water channels following AKI plays a pivotal role in ALI, the mechanism of its dysregulation has not been elucidated. Here, we examined the involvement of a typical oxidative stress-inducing uremic toxin, indoxyl sulfate (IS), in the dysregulation of the pulmonary predominant water channel, aquaporin 5 (AQP-5), in bilateral nephrectomy (BNx)-induced AKI model rats. BNx evoked AKI with the increases in serum creatinine (SCr), blood urea nitrogen (BUN) and serum IS levels and exhibited thickening of interstitial tissue in the lung. Administration of AST-120, clinically-used oral spherical adsorptive carbon beads, resulted in a significant decrease in serum IS level and thickening of interstitial tissue, which was accompanied with the decreases in IS accumulation in various tissues, especially lung. Interestingly, a significant decrease in AQP-5 expression of lung was observed in BNx rats. Moreover, the BNx-induced decrease in pulmonary AQP-5 protein expression was markedly restored by oral administration of AST-120. These results suggest that BNx-induced AKI causes dysregulation of pulmonary AQP-5 expression, in which IS could play a toxico-physiological role as a mediator involved in renopulmonary crosstalk

Assessing the pyrogenicity of whole influenza virus particle vaccine in cynomolgus macaques

Among inactivated influenza vaccines, the whole virus particle vaccine (WPV) elicits superior priming responses to split virus vaccine (SV) in efficiently inducing humoral and cellular immunity. However, there is concern for undesired adverse events such as fever for WPV due to its potent immunogenicity. Therefore, this study investigated the febrile response induced by subcutaneous injection with quadriva-lent inactivated influenza vaccines of good manufacturing grade for pharmaceutical or investigational products in cynomolgus macaques. Body temperature was increased by 1 degrees C-2 degrees C for 6-12 h after WPV administration at the first vaccination but not at the second shot, whereas SV did not affect body temperature at both points. Given the potent priming ability of WPV, WPV-induced fever may be attrib-uted to immune responses that uniquely occur during priming. Since WPV-induced fever was blunted by pretreatment with indomethacin (a cyclooxygenase inhibitor), the febrile response by WPV is considered to depend on the increase in prostaglandins synthesized by cyclooxygenase. In addition, WPV, but not SV, induced the elevation of type I interferons and monocyte chemotactic protein 1 in the plasma; these fac-tors may be responsible for pyrogenicity caused by WPV, as they can increase prostaglandins in the brain. Notably, sufficient antibody responses were acquired by half the amount of WPV without causing fever, suggesting that excessive immune responses to trigger the febrile response is not required for acquired immunity induction. Thus, we propose that WPV with a reduced antigen dose should be evaluated for potential clinical usage, especially in naive populations. (c) 2022 The Authors. Published by Elsevier Ltd

Meclofenamate elicits a nephropreventing effect in a rat model of ischemic acute kidney injury by suppressing indoxyl sulfate production and restoring renal organic anion transporters

Indoxyl sulfate (IS), a putative low-molecular weight uremic toxin, is excreted in the urine under normal kidney function, but is retained in the circulation and tissues during renal dysfunction in acute kidney injury (AKI) and chronic kidney disease (CKD). IS, which is one of the most potent inducers of oxidative stress in the kidney and cardiovascular system, is enzymatically produced in the liver from indole by cytochrome P450-mediated hydroxylation to indoxyl, followed by sulfotransferase (SULT)-mediated sulfate conjugation. We used rat liver S9 fraction to identify inhibitors of IS production. After testing several compounds, including phytochemical polyphenols, we identified meclofenamate as a potent inhibitor of IS production with an apparent IC50 value of 1.34 M. Ischemia/reperfusion (I/R) of rat kidney caused a marked elevation in the serum IS concentration 48 hr after surgery. However, intravenous administration of meclofenamate (10 mg/kg) significantly suppressed this increase in the serum level of IS. Moreover, IS concentrations in both kidney and liver were dramatically elevated by renal I/R treatment, but this increase was blocked by meclofenamate. Serum creatinine and blood urea nitrogen were markedly elevated in rats after renal I/R treatment, but these increases were significantly restored by administration of meclofenamate. Renal expression of both basolateral membrane-localized organic anion transporters rOAT1 and rOAT3 was downregulated by I/R treatment. However, expression of rOAT1 and rOAT3 recovered after administration of meclofenamate, which is associated with the inhibition of I/R-evoked elevation of PGE2. Our results suggest that meclofenamate inhibits hepatic SULT-mediated production of IS, thereby suppressing serum and renal accumulation of IS. Meclofenamate also prevents the PGE2-dependent downregulation of rOAT1 and rOAT3 expression. In conclusion, meclofenamate was found to elicit a nephropreventive effect in ischemic AKI

Hepatic Sulfotransferase as a Nephropreventing Target by Suppression of the Uremic Toxin Indoxyl Sulfate Accumulation in Ischemic Acute Kidney Injury

Ischemia/reperfusion (I/R)-induced acute kidney injury (AKI) is evoked by diverse pathophysiological conditions and/or surgical procedures. Here, we evaluated the nephropreventive effect of sulfotransferase (SULT) inhibitors, quercetin and resveratrol, which hamper hepatic indoxyl sulfate (IS) production. I/R of the kidney caused severe renal injury with marked accumulation of serum and renal IS and urinary excretion of kidney injury molecule-1. Oral administration of AST-120 resulted in a significant restoration of kidney injury, suggesting that uremic toxins, which can be suppressed or adsorbed by AST-120 in the intestine, contribute to the progression or development of I/R-induced AKI. Oral administration of resveratrol or quercetin, SULT inhibitors, suppressed IS accumulation, accompanied by significant amelioration of renal dysfunction. The expression of nuclear factor E2-related factor 2 (Nrf2) in the renal nuclear fractions was markedly elevated by renal I/R, but suppressed by treatment with SULT inhibitors. IS is primarily taken up by HK-2 cells derived from human proximal tubular cells via organic anion transporters, which then evokes activation of Nrf2, most likely due to intracellular oxidative stress. Renal basolateral organic anion transporters OAT1 and OAT3, which mediate renal tubular uptake of IS in basolateral membrane, were markedly down-regulated by renal I/R, but restored by SULT inhibitors. Our results suggest that renal accumulation of IS in ischemic AKI induces oxidative stress and downregulation of organic anion transporters resulting in kidney damage, which could be restored to some extent by inhibiting hepatic SULT activity as a nephropreventive target