The use of deuterium-incorporated bioactive compounds is an efficient method for tracing their metabolic fate and for quantitative analysis by mass spectrometry without complicated HPLC separation even if their amounts are extremely small. Plant sphingolipids and their metabolites, which have C4, 8-olefins on a common backbone as a sphingoid base, show unique and fascinating bioactivities compared to those of sphingolipids in mammals. However, the functional and metabolic mechanisms of exogenous plant sphingolipids have not been elucidated due to the difficulty in distinguishing exogenous sphingolipids from endogenous sphingolipids having the same polarity and same molecular weight by mass spectrometric analysis. Their roles might be elucidated by the use of deuterated probes with original biological and physicochemical properties. In this study, we designed (2S,3R,4E,8Z)-2-aminooctadeca-4,8-diene-17,17,18,18,18-d5-1,3-diol (penta-deuterium-labeled 4E, 8Z-sphingadienine) as a tracer for exogenous metabolic studies. In addition, the sphingadienine was confirmed to be metabolized in HEK293 cells and showed distinct peaks in mass spectrometric analysis.

The main lesion of cisplatin nephrotoxicity is damage to proximal tubular cells due to increased apoptosis via the mitochondrial and death receptor pathways, which may be alleviated by appropriate promotion of autophagy. Fenofibrate, a peroxisome proliferator-activated receptor-alpha (PPAR-α) activator, is recently reported to promote autophagy as well as protect against cisplatin nephrotoxicity, although the mechanisms were only partially analyzed. Here, the detailed mechanisms of these putative protective effects were investigated in a murine renal proximal tubular (mProx) cell line. Fenofibrate attenuated cisplatin-induced apoptosis of mProx cells based on flow cytometry. As for the mitochondrial apoptotic pathway, the reagent reduced cisplatin-stimulated caspase-3 activation by decreasing the phosphorylation of p53, JNK, and 14-3-3, cytosolic and mitochondrial Puma accumulation, cytochrome C release to the cytosol, and resulting cytosolic caspase-9 activation. Fenofibrate also decreased cisplatin-stimulated activation of caspases-8 by suppressing MAPK and NFkB pathways and reducing the gene expression of TNF-α, TL1A, and Fas, main mediators of the death receptor apoptotic pathway. Autophagy defined by p62 reduction and an increase in LC3 II/I was promoted by fenofibrate in mProx cells under starvation. Autophagy inhibition using 3-MA further increased basal and cisplatin-induced caspase-3 and -8 activation, but had no influence on the inhibitory effects of fenofibrate on caspase activation. In conclusion, our study suggests fenofibrate to be a candidate agent to mitigate cisplatin nephrotoxicity by inhibiting the mitochondrial and death apoptotic pathways rather than by promoting autophagy.

We report on an 80-year-old man diagnosed with Fanconi syndrome induced by mizoribine after 4 weeks of administration to treat membranous nephropathy. Mizoribine is an oral immunosuppressant that inhibits inosine monophosphate dehydrogenase and is widely used in Japan for the treatment of autoimmune diseases and nephrotic syndrome, as well as after renal transplantation. Acquired Fanconi syndrome is often caused by drugs (antibacterial, antiviral, anticancer, and anticonvulsant drugs) and is sometimes caused by autoimmune diseases, monoclonal light chain-associated diseases, or heavy metal poisoning. In our patient, hypokalemia, hypophosphatemia, glucosuria, hypouricemia, and severe proteinuria resolved gradually after discontinuation of mizoribine administration, despite oral administration of prednisolone followed by a single intravenous injection of rituximab. The patient was ultimately diagnosed with Fanconi syndrome induced by mizoribine based on his clinical course and his typical laboratory data with the absence of proximal tubular acidosis. To our knowledge, this is the first report of Fanconi syndrome possibly induced by mizoribine. Although the precise mechanism by which mizoribine induces proximal tubular dysfunction is unknown, we suggest that nephrologists should be aware of the onset of Fanconi syndrome, a rare complication during mizoribine treatment.

The extracellular accumulation of aggregated amyloid-β (Aβ) in the brain leads to the early pathology of Alzheimer’s disease (AD). The administration of exogenous plant-type ceramides into AD model mice can promote the release of neuronal exosomes, a subtype of extracellular vesicles, that can mediate Aβ clearance. In vitro studies showed that the length of fatty acids in mammalian-type ceramides is crucial for promoting neuronal exosome release. Therefore, investigating the structures of plant ceramides is important for evaluating the potential in releasing exosomes to remove Aβ. In this study, we assessed plant ceramide species with D-erythro-(4E,8Z)-sphingadienine and D-erythro-(8Z)-phytosphingenine as sphingoid bases that differ from mammalian-type species. Some plant ceramides were more effective than mammalian ceramides at stimulating exosome release. In addition, using deuterium chemistry-based lipidomics, most exogenous plant ceramides were confirmed to be derived from exosomes. These results suggest that the ceramide-dependent upregulation of exosome release may promote the release of exogenous ceramides from cells, and plant ceramides with long-chain fatty acids can effectively release neuronal exosomes and prevent AD pathology.

Histamines suppress epidermal keratinocyte differentiation. Previously, we reported that konjac ceramide (kCer) suppresses histamine-stimulated cell migration of HaCaT keratinocytes. kCer specifically binds to Nrp1 and does not interact with histamine receptors. The signaling mechanism of kCer in HaCaT cells is also controlled by an intracellular signaling cascade activated by the Sema3A-Nrp1 pathway. In the present study, we demonstrated that kCer treatment induced HaCaT keratinocyte differentiation after migration of immature cells. kCer-induced HaCaT cell differentiation was accompanied by some features of keratinocyte differentiation markers. kCer induced activating phosphorylation of p38MAPK and c-Fos, which increased the protein levels of involucrin that was the latter differentiation marker. In addition, we demonstrated that the effects of both kCer and histamines are regulated by an intracellular mechanism of Rac1 activation/RhoA inhibition downstream of the Sema3A/Nrp1 receptor and histamine/GPCR pathways. In summary, the effects of kCer on cell migration and cell differentiation are regulated by cascade crosstalk between downstream Nrp1 and histamine-GPCR pathways in HaCaT cells.

BACKGROUND:Cisplatin-induced injury of renal proximal tubular cells results basically from increased apoptosis via mitochondrial damage, and is mitigated by appropriate enhancement of autophagy. Peroxisome proliferator-activated receptor-delta (PPAR-δ) reportedly protects against not only mitochondrial damages but also enhances autophagy. Thus, PPAR-δ may protect against cisplatin-induced kidney injury.METHODS:We examined the protective effects of PPAR-δ activation on cisplatin-induced cellular injury and their detailed mechanisms in a murine renal proximal tubular (mProx) cell line using GW0742, an authentic PPAR-δ activator. Cisplatin-induced cell damages were evaluated by TUNEL assay and immunoblot analyses for p53, 14-3-3, Bax, Bcl2, cytochrome C, and activated caspases. Autophagy status was examined by immunoblot analyses for p62 and LC3.RESULTS:GW0742 suppressed cisplatin-induced apoptosis of mProx cells by reducing the activation of caspase-3 via attenuating the phosphorylation of p53 and 14-3-3, mitochondrial Bax accumulation, cytochrome C release from mitochondria to the cytosol and ensuing cytosolic caspase-9 activation. In contrast, GW0742 did not diminish cisplatin-enhanced activation of caspases-8 or -12 as extrinsic or endothelium reticulum apoptotic pathways, respectively. The inhibitory effect of GW0742 on cisplatin-induced caspase-3 activation was significantly diminished by silencing of the PPAR-δ gene expression. GW0742 itself had no influence on starvation-stimulated or cisplatin-induced autophagy in mProx cells, suggesting that the protective effects were not mediated by autophagy modification.CONCLUSION:Our results indicate that GW0742 may serve as a candidate agent to mitigate cisplatin nephrotoxicity via inhibiting the mitochondrial apoptotic pathway considerably depending on PPAR-δ, without modulating autophagy.

Although 11-ketotestosterone (11KT) and testosterone (T) are major androgens in both teleosts and humans, their 5α-reduced derivatives produced by steroid 5α-reductase (SRD5A/srd5a), i.e., 11-ketodihydrotestosterone (11KDHT) and 5α-dihydrotestosterone (DHT), remains poorly characterized, especially in teleosts. In this study, we compared the presence and production of DHT and 11KDHT in Japanese eels and humans. Plasma 11KT concentrations were similar in both male and female eels, whereas T levels were much higher in females. In accordance with the levels of their precursors, 11KDHT levels did not show sexual dimorphism, whereas DHT levels were much higher in females. It is noteworthy that plasma DHT levels in female eels were higher than those in men. In addition, plasma 11KDHT was undetectable in both sexes in humans, despite the presence of 11KT. Three srd5a genes ( srd5a1 , srd5a2a and srd5a2b ) were cloned from eel gonads. All three srd5a genes were expressed in the ovary, whereas only both srd5a2 genes were expressed in the testis. Human SRD5A1 was expressed in testis, ovary and adrenal, whereas SRD5A2 was expressed only in testis. Human SRD5A1, SRD5A2 and both eel srd5a2 isoforms catalyzed the conversion of T and 11KT into DHT and 11KDHT, respectively, whereas only eel srd5a1 converted T into DHT. DHT and 11KDHT activated eel androgen receptor (ar)α-mediated transactivation as similar fashion to T and 11KT. In contrast, human AR and eel arβ were activated by DHT and11KDHT more strongly than T and 11KT. These results indicate that in teleosts, DHT and 11KDHT may be important 5α-reduced androgens produced in the gonads. In contrast, DHT is the only major 5α-reduced androgens in healthy humans.

Background Dietary sphingolipids have various biofunctions, including skin barrier improvement and anti-inflammatory and anti-carcinoma properties. Long-chain bases (LCBs), the essential backbones of sphingolipids, are expected to be important for these bioactivities, and they vary structurally between species. Given these findings, however, the absorption dynamics of each LCB remain unclear. Methods In this study, five structurally different LCBs were prepared from glucosylceramides (GlcCers) with LCB 18:2(4E,8Z);2OH and LCB 18:2(4E,8E);2OH moieties derived from konjac tuber ( Amorphophallus konjac ), from GlcCers with an LCB 18(9Me):2(4E,8E);2OH moiety derived from Tamogi mushroom ( Pleurotus cornucopiae var. citrinopileatus ), and from ceramide 2-aminoethyphosphonate with LCB 18:3(4E,8E,10E);2OH moiety and LCB 18(9Me):3(4E,8E,10E);2OH moiety derived from giant scallop ( Mizuhopecten yessoensis ), and their absorption percentages and metabolite levels were analyzed using a lymph-duct-cannulated rat model via liquid chromatography tandem mass spectrometry (LC/MS/MS) with a multistage fragmentation method. Results The five orally administered LCBs were absorbed and detected in chyle (lipid-containing lymph) as LCBs and several metabolites including ceramides, hexosylceramides, and sphingomyelins. The absorption percentages of LCBs were 0.10–1.17%, depending on their structure. The absorption percentage of LCB 18:2(4E,8Z);2OH was the highest (1.17%), whereas that of LCB 18:3(4E,8E,10E);2OH was the lowest (0.10%). The amount of sphingomyelin with an LCB 18:2(4E,8Z);2OH moiety in chyle was particularly higher than sphingomyelins with other LCB moieties. Conclusions Structural differences among LCBs, particularly geometric isomerism at the C8–C9 position, significantly affected the absorption percentages and ratio of metabolites. This is the first report to elucidate that the absorption and metabolism of sphingolipids are dependent on their LCB structure. These results could be used to develop functional foods that are more readily absorbed.

Porcine steroid hormone profiles have some unique characteristics. We previously studied human and murine steroidogenesis using steroidogenic cells-derived from mesenchymal stem cells (MSCs). To investigate porcine steroidogenesis, we induced steroidogenic cells from porcine subcutaneous preadipocytes (PSPA cells), which originate from MSCs. Using cAMP, adenovirus-mediated introduction of steroidogenic factor-1 (SF-1)/adrenal 4-binding protein (Ad4BP) induced the differentiation of PSPA cells into sex steroid-producing cells. Introducing SF-1/Ad4BP also induced the aldo-keto reductase 1C1 (AKR1C1) gene. Porcine AKR1C1 had 17β-hydroxysteroid dehydrogenase activity, which converts androstenedione and 11-ketoandrostenedione into testosterone (T) and 11-ketotestosteorne (11KT). Furthermore, differentiated cells expressed hydroxysteroid 11β-dehydrogenase 2 (HSD11B2) and produced 11KT. HSD11B2 was expressed in testicular Leydig cells and the adrenal cortex. 11KT was present in the plasma of both immature male and female pigs, with slightly higher levels in the male pigs. T levels were much higher in the male pigs. It is noteworthy that in the female pigs, the 11KT levels were >10-fold higher than the T levels. However, castration altered the 11KT and T plasma profiles in the male pigs to near those of the females. 11KT induced endothelial nitric oxide synthase (eNOS) in porcine vascular endothelial cells. These results indicate that 11KT is produced in porcine adrenal glands and testes, and may regulate cardiovascular functions through eNOS expression.

Ceramides, a type of sphingolipid, are cell membrane components and lipid mediators that modulate a variety of cell functions. In plants, ceramides are mostly present in a glucosylated glucosylceramide (GlcCer) form. We previously showed that oral administration of konjac-derived GlcCer to a mouse model of Alzheimer’s disease reduced brain amyloid-β and amyloid plaques. Dietary plant GlcCer compounds are absorbed as ceramides, but it is unclear whether they can cross the blood-brain barrier (BBB). Herein, we evaluated the BBB permeability of synthetic plant-type ceramides (4, 8-sphingadienine, d18:2) using mouse and BBB cell culture models, and found that they could permeate the BBB both in vivo and in vitro. In addition, administrated ceramides were partially metabolized to other sphingolipid species, namely sphingomyelin (SM) and GlcCer, while crossing the BBB. Thus, plant ceramides can cross the BBB, suggesting that ceramides and their metabolites might affect brain functions.

Short-chain fatty acids (SCFAs), including acetate, butyrate, and propionate, are produced when colonic bacteria in the human gastrointestinal tract ferment undigested fibers. Free fatty acid receptor 2 (FFA2) and FFA3 are G-protein-coupled receptors recently identified as SCFA receptors that may modulate inflammation. We previously showed through in vitro experiments that SCFAs activate FFA2 and FFA3, thereby mitigating inflammation in human renal cortical epithelial cells. This study used a murine model of adenine-induced renal failure to investigate whether or not SCFAs can prevent the progression of renal damage. We also examined whether or not these FFA2 and FFA3 proteins have some roles in this protective mechanism in vivo. Immunohistochemical analyses of mouse kidneys showed that FFA2 and FFA3 proteins were expressed mainly in the distal renal tubules and collecting tubules. First, we observed that the administration of propionate mitigated the renal dysfunction and pathological deterioration caused by adenine. Consistent with this, the expression of inflammatory cytokines and fibrosis-related genes was reduced. Furthermore, the mitigation of adenine-induced renal damage by the administration of propionate was significantly attenuated in FFA2(-/-) and FFA3(-/-) mice. Therefore, the administration of propionate significantly protects against adenine-induced renal failure, at least in part, via the FFA2 and FFA3 pathways. Our data suggest that FFA2 and FFA3 are potential new therapeutic targets for preventing or delaying the progression of chronic kidney disease.

Exosomes are extracellular vesicles that mediate the transport of intracellular molecules, including neurodegenerative agents. Exogenously administrated ceramides have been implicated in the acceleration of exosome production by neurons; however, the molecular machinery involved in this process is unknown. Here, we found that ceramides, especially those consisting of long fatty acids, were internalized into the endocytic pathway in neuroblastoma SH-SY5Y cells to induce exosome secretion through lysosome-associated protein transmembrane 4B (LAPTM4B). Knockdown of LAPTM4B inhibited the ceramide-mediated increase in exosome release completely. Fluorescence microscopy observations indicated that exogenous ceramides promote the transport of multivesicular bodies to the plasma membranes in a LAPTM4B-dependent manner. Similarly, inhibition of acid ceramidase, which tends to induce intracellular ceramide accumulation, increased exosome production by SH-SY5Y cells in a LAPTM4B-dependent manner. Furthermore, the level of amyloid-ß protein (Aß) was decreased in neuronal cells following treatment with exogenous ceramide or inhibition of acid ceramidase, and this effect was attributed to the LAPTM4B-dependent efflux of Aß-containing exosomes. Overall, these findings reveal the novel machinery involved in exosome secretion regulated by ceramides and LAPTM4B, and may contribute to efforts to ameliorate the cellular accumulation of neurodegenerative agents such as Aß.

BACKGROUND:Chronic hypoxia may play a pivotal role in the development of diabetic nephropathy (DN). However, the precise mechanisms underlying progressive hypoxia-induced glomerular injury remain unclear.METHODS:We housed db/db mice in a hypoxia chamber (12% O2) for up to 16 weeks beginning at 8 weeks of age. Various urine, serum and kidney abnormalities and glomerular messenger RNA (mRNA) expression were compared with those in age-matched db/db mice housed under normoxia.RESULTS:Levels of urinary albumin and podocalyxin (PCX) were significantly higher in hypoxic mice early during hypoxia. Ultracentrifugation of urine samples revealed that podocytes in the hypoxic mice shed PCX-positive microparticles into the urine. After 16 weeks of hypoxia, the mice also had higher hematocrits with lower serum glucose and various degrees of mesangiolytic glomerulosclerosis with microaneurysms and the infrequent occurrence of nodular lesions. Immunohistologically, hypoxic mice showed significantly decreased endothelial cell densities early during hypoxia and decreased podocyte densities later. In both hypoxic and normoxic mice, glomerular macrophage and transforming growth factor-β1 (TGF-β1) staining significantly increased with aging, without changes in vascular endothelial growth factor or endothelial nitric oxide synthase (eNOS). Glomerular mRNA expression of monocyte chemoattractant protein-1, eNOS and TGF-β1 was significantly enhanced in the hypoxic mice.CONCLUSIONS:These results indicate that chronic hypoxia induces advanced glomerulosclerosis with accelerated albuminuria triggered by mesangiolysis and podocyte injury in a murine model of DN.

PNU-120596 is a classical positive allosteric modulator (PAM) of α7 nicotinic acetylcholine receptor (α7 nAChR) and widely used to investigate the effect of α7 nAChR activation on several inflammation-associated diseases including rheumatoid arthritis, inflammatory bowel disease and cerebral ischemia. In this study, we report that PNU-120596 directly inhibits p38 mitogen-activated protein kinase (MAPK) activity. In 293A cells, p38 MAPK phosphorylation by several factors (oxidative stress, osmotic stress, TNF-α, or muscarinic stimulation) was inhibited by PNU-120596 as well as p38 MAPK inhibitor BIRB-796. Inhibition of p38 MAPK phosphorylation by PNU-120596 was not affected by α7 nAChR antagonist, methyllycaconitine (MLA). In vitro kinase assay revealed that PNU-120596 directly inhibits p38α MAPK-induced activating transcription factor 2 (ATF2) phosphorylation. MKK6-induced phosphorylation of p38α MAPK was also inhibited by PNU-120596. Real-time monitoring of binding to p38α MAPK using fluoroprobe SKF-86002 showed quite rapid binding of PNU-120596 compared to BIRB-796 which is known as a slow binder. Finally, we showed that PNU-120596 suppressed LPS-induced phosphorylation of p38 MAPK and expression of inflammatory factors including TNF-α, IL-6 and COX-2, independent on α7 nAChR activity in microglial cell BV-2. Thus, PNU-120596 might exert an anti-inflammatory effect through not only α7 nAChR potentiation but also direct inhibition of p38 MAPK.

The somatic haploidy is unstable in diplontic animals, but cellular processes determining haploid stability remain elusive. Here, we found that inhibition of mevalonate pathway by pitavastatin, a widely used cholesterol-lowering drug, drastically destabilized the haploid state in HAP1 cells. Interestingly, cholesterol supplementation did not restore haploid stability in pitavastatin-treated cells, and cholesterol inhibitor U18666A did not phenocopy haploid destabilization. These results ruled out the involvement of cholesterol in haploid stability. Besides cholesterol perturbation, pitavastatin induced endoplasmic reticulum (ER) stress, the suppression of which by a chemical chaperon significantly restored haploid stability in pitavastatin-treated cells. Our data demonstrate the involvement of the mevalonate pathway in the stability of the haploid state in human somatic cells through managing ER stress, highlighting a novel link between ploidy and ER homeostatic control.

Ketone bodies, including acetoacetate and β-hydroxybutyrate (βOHB), are produced from acetyl coenzyme A in the liver and then secreted into the blood. These molecules are a source of energy for peripheral tissues during exercise or fasting. βOHB has been reported to inhibit histone deacetylases (HDACs) 1, 3, and 4 in human embryonic kidney 293 cells. Thus, βOHB may regulate epigenetics by modulating HDACs. There have been several reports that the administration of βOHB or induction of a physiological state of ketosis has an antitumor effect; however, the mechanism remains unclear. The aim of this study was to investigate whether βOHB enhances cisplatin-induced apoptosis in hepatocellular carcinoma (HCC) cells by modulating activity and/or expression of HDACs. We found that βOHB significantly enhanced cisplatin-induced apoptosis and cleavage of caspase-3 and -8 in HCC cells. Further, βOHB significantly decreased the expression of HDCA 3/5/6 and survivin in liver hepatocellular (HepG2) cells. In HDAC3/6 gene silencing, survivin expression was significantly decreased, and cisplatin-induced cleavage of caspase-3 was significantly enhanced compared with control in HepG2 cells. In conclusion, βOHB enhanced cisplatin-induced apoptosis via HDAC3/6 inhibition/survivin axis in HepG2 cells, which suggests that βOHB could be a new adjuvant agent for cisplatin chemotherapy.

Common management of renal transplant recipients includes episodic renal biopsy based on clinical findings such as an increase in proteinuria or serum creatinine. When antibody-related rejection is suspected from the renal biopsy, subsequent testing for donor-specific antibodies (DSAs) is performed. We instead performed preemptive screening of asymptomatic post-renal transplant recipients for DSAs prior to renal biopsy. In this case, a 30-year-old woman with a secondary transplant was positive for 61 anti-HLA antibodies of class I and class II, among which DQ2 was a DSA with a mean fluorescence index of 2039. The patient had a living kidney transplant 9 years earlier. She had never been diagnosed with rejection, her serum creatinine was around 1.0 mg/dL, and her proteinuria was negative. Following the positive DSA result, a renal biopsy was performed, and she was diagnosed as C4d-negative chronic-active antibody-mediated rejection (CAABMR) with a Banff score of cg1b, (g + ptc) ≥ 2, and C4d 0. Intravenous steroid pulse, deoxyspagarin, antithymocyte globulin, rituximab, and oral everolimus were administrated. The treatment resulted in a gradual decrease in the DSA, which became negative 1 year later. The patient's serum creatinine remains around 1.0 mg/dL, and proteinuria remains negative. Treatments for advanced CAABMR are often expensive and ineffective. Our present case suggests that early detection and treatment through preemptive HLA antibody screening could improve the prognosis of renal transplants.

Konjac ceramide (kCer) is a plant-type ceramide composed of various long-chain bases and α-hydroxyl fatty acids. The presence of d4t,8t-sphingadienine is essential for semaphorin 3A (Sema3A)-like activity. Herein, we examined the three neuropilin 1 (Nrp1) domains (a1a2, b1b2, or c), and found that a1a2 binds to d4t,8t-kCer and possesses Sema3A-like activity. kCer binds to Nrp1 with a weak affinity of μM dissociation constant (Kd). We wondered whether bovine serum albumin could influence the ligand–receptor interaction that a1a2 has with a single high affinity binding site for kCer (Kd in nM range). In the present study we demonstrated the influence of bovine serum albumin. Thermal denaturation indicates that the a1a2 domain may include intrinsically disordered region (IDR)-like flexibility. A potential interaction site on the a1 module was explored by molecular docking, which revealed a possible Nrp1 activation mechanism, in which kCer binds to Site A close to the Sema3A-binding region of the a1a2 domain. The a1 module then accesses a2 as the IDR-like flexibility becomes ordered via kCer-induced protein rigidity of a1a2. This induces intramolecular interaction between a1 and a2 through a slight change in protein secondary structure.

BACKGROUND:Oxidative stress is now recognized to be an important therapeutic target in kidney diseases. However, there are currently no biomarkers that can be used clinically to diagnose renal oxidative stress. METHODS:A rapid assay system for urinary thioredoxin 1, an oxidative stress-dependent biomarker of acute kidney injury (AKI), was developed as a chemiluminescence enzyme immunoassay and validated analytically and clinically. RESULTS:Analytic evaluation revealed that hemolytic hemoglobin caused measurements to be abnormally high, above the detectable range. However, urine sediment containing red blood cells did not affect the measurements. Assays using our proposed chemiluminescence enzyme immunoassay were completed within as little as 6 min, whereas a conventional ELISA > 4 h. Aciduria <pH 6.0 led to a significant underestimation of thioredoxin 1 concentrations. However, the effects of aciduria were completely reversible with use of a buffer developed for pH adjustment. Urinary thioredoxin 1 was increased in patients with AKI, but was unaffected by extrarenal oxidative stress diseases, including hypoxemia and myocardial infarction, or by chronic kidney disease in which serum creatinine concentrations were comparable. CONCLUSIONS:These results suggest that the chemiluminescent enzyme immunoassay system for urinary thioredoxin 1 enables rapid and specific diagnosis of AKI associated with oxidative stress.

Background: Hepatocellular carcinoma (HCC) is a major cause of cancer death worldwide and establishment of new chemotherapies for HCC is urgently needed. GPR41 [free fatty acid receptor 3 (FFA3)] is a G protein-coupled receptor for short chain fatty acids, including acetate, propionate, and butyrate. In our previous study, we showed that propionate enhances the cytotoxic effect of cisplatin in HCC cells and that this mechanism is dependent on inhibition of histone deacetylases (HDACs) via GPR41/FFA3. However, the antitumor action of GPR41/FFA3 has not been elucidated. Methods: In this study, we examined AR420626 as a GPR41-selective agonist in HepG2 and HLE cells. Nude mice were used for HepG2 xenograft studies. The apoptotic effect of AR420626 was evaluated using flow cytometry analysis. Expression of apoptosis-related proteins and HDACs was evaluated by Western immunoblot. Gene silencing of HDAC 3/5/7 and GPR41 was performed using small interfering RNA. Expression of TNF-α mRNA was evaluated by TaqMan real-time polymerase chain reaction. Results: We found that AR420626, a selective GPR41/FFA3 agonist, suppressed growth of HepG2 xenografts and inhibited proliferation of HCC cells by inducing apoptosis. AR420626 induced proteasome activation through mTOR phosphorylation, which reduced HDAC proteins, and then increased expression of TNF-α. Conclusion: AR420626, a selective GPR41/FFA3 agonist, may be a candidate as a therapeutic agent for HCC.