Downregulation of OATP2B1 by proinflammatory cytokines leads to 5-ASA hyposensitivity in Ulcerative colitis.

5-Aminosalicylic acid (5-ASA) is a first-line agent in both remission and maintenance therapy for ulcerative colitis (UC). However, the mucosal concentration of 5-ASA was significantly lower in patients with severe histological inflammation, which further led to a poor response to 5-ASA treatment. Our study aimed to clarify the mechanism of 5-ASA uptake into colonic epithelial cells and to further explore the reason for the decreased colonic mucosal 5-ASA concentration in UC patients. Our results demonstrated that the colonic 5-ASA concentration was notably reduced in DSS-induced colitis mice and inversely correlated with colonic inflammation. 5-ASA was not a substrate of carnitine/organic cation transporter 1/2 (OCTN1/2) or multidrug resistance protein 1 (MDR1), whereas organic anion transporting polypeptide 2B1 (OATP2B1) and sodium-coupled monocarboxylate transporter 1 (SMCT1) mediated the uptake of 5-ASA, with a greater contribution from OATP2B1 than SMCT1. Inhibitors and siRNAs targeting OATP2B1 significantly reduced 5-ASA absorption in colonic cell lines. Moreover, OATP2B1 expression was dramatically downregulated in colon tissues from UC patients and dextran sodium sulfate (DSS)-induced colitis mice, and was also negatively correlated with colonic inflammation. Mechanistically, mixed proinflammatory cytokines downregulated the expression of OATP2B1 in a time- and concentration-dependent manner through the hepatocyte nuclear factor 4 α (HNF4α) pathway. In conclusion, OATP2B1 was the pivotal transporter involved in colonic 5-ASA uptake, which indicated that inducing OATP2B1 expression may be a strategy to promote 5-ASA uptake and further improve the concentration and anti-inflammatory efficacy of 5-ASA in UC.

Metformin inhibits OCTN1- and OCTN2-mediated hepatic accumulation of doxorubicin and alleviates its hepatotoxicity in mice.

Doxorubicin (DOX) is a widely used antitumor agent; however, its clinical application is limited by dose-related organ damage. Because organic cation/carnitine transporters (OCTN1 and OCTN2), which are critical for DOX uptake, are highly expressed in hepatocytes, we aimed to elucidate the role of these transporters in hepatic DOX uptake. The results indicated that inhibitors and RNA interference both significantly reduced DOX accumulation in HepG2 and HepaRG cells, suggesting that OCTN1/2 contribute substantially to DOX uptake by hepatocytes. To determine whether metformin (MET, an inhibitor of OCTN1 and OCTN2) ameliorates DOX-induced hepatotoxicity, we conducted in vitro and in vivo studies. MET (1-100 µM) inhibited DOX (500 nM) accumulation and cytotoxicity in vitro in a concentration-dependent manner. Furthermore, intravenous MET administration at 250 or 500 mg/kg or by gavage at 50, 100, or 200 mg/kg reduced DOX (8 mg/kg) accumulation in a dose-dependent manner in the mouse liver and attenuated the release of alanine aminotransferase, aspartate aminotransferase, and carboxylesterase 1. Additionally, MET reduced the distribution of DOX in the heart, liver, and kidney and enhanced the urinary elimination of DOX; however, it did not increase the nephric toxicity of DOX. In conclusion, our study demonstrated that MET alleviates DOX hepatotoxicity by inhibiting OCTN1- and OCTN2-mediated DOX uptake in vitro (mouse hepatocytes and HepaRG or HepG2 cells) and in mice.

Oligopeptide/Histidine Transporter PHT1 and PHT2 - Function, Regulation, and Pathophysiological Implications Specifically in Immunoregulation.

The oligopeptide/histidine transporters PHT1 and PHT2, two mammalian solute carrier family 15A proteins, mediate the transmembrane transport of histidine and some di/tripeptides via proton gradient. PHT1 and PHT2 are distributed in a variety of tissues but are preferentially expressed in immune cells and localize to the lysosome-related organelles. Studies have reported the relationships between PHT1/PHT2 and immune diseases. PHT1 and PHT2 participate in the regulation of lysosomal homeostasis and lysosome-associated signaling pathways through their transport and nontransport functions, playing important roles in inflammatory diseases. In this review, we summarize recent research on PHT1 and PHT2, aiming to provide reference for their further biological research and as targets for drug design.

Inhibition of multiple uptake transporters in cardiomyocytes/mitochondria alleviates doxorubicin-induced cardiotoxicity.

Doxorubicin (DOX) has been widely used to treat various tumors; however, DOX-induced cardiotoxicity limits its utilization. Since high accumulation of DOX in cardiomyocytes/mitochondria is the key reason, we aimed to clarify the mechanisms of DOX uptake and explore whether selectively inhibiting DOX uptake transporters would attenuate DOX accumulation and cardiotoxicity. Our results demonstrated that OCTN1/OCTN2/PMAT (organic cation/carnitine transporter 1/2 or plasma membrane monoamine transporter), especially OCTN2, played crucial roles in DOX uptake in cardiomyocytes, while OCTN2 and OCTN1 contributed to DOX transmembrane transport in mitochondria. Metformin (1-100 µM) concentration-dependently reduced DOX (5 µM for accumulation, 500 nM for cytotoxicity) concentration and toxicity in cardiomyocytes/mitochondria via inhibition of OCTN1-, OCTN2- and PMAT-mediated DOX uptake but did not affect its efflux. Furthermore, metformin (iv: 250 and 500 mg/kg or ig: 50, 100 and 200 mg/kg) could dose-dependently reduce DOX (8 mg/kg) accumulation in mouse myocardium and attenuated its cardiotoxicity. In addition, metformin (1-100 µM) did not impair DOX efficacy in breast cancer or leukemia cells. In conclusion, our study clarified the role of multiple transporters, especially OCTN2, in DOX uptake in cardiomyocytes/mitochondria; metformin alleviated DOX-induced cardiotoxicity without compromising its antitumor efficacy by selective inhibition of multiple transporters mediated DOX accumulation in myocardium/mitochondria.

Fecal microbiota transplantation inhibits colorectal cancer progression: Reversing intestinal microbial dysbiosis to enhance anti-cancer immune responses.

Many lines of evidence demonstrate the associations of colorectal cancer (CRC) with intestinal microbial dysbiosis. Recent reports have suggested that maintaining the homeostasis of microbiota and host might be beneficial to CRC patients, but the underlying mechanisms remain unclear. In this study, we established a CRC mouse model of microbial dysbiosis and evaluated the effects of fecal microbiota transplantation (FMT) on CRC progression. Azomethane and dextran sodium sulfate were used to induce CRC and microbial dysbiosis in mice. Intestinal microbes from healthy mice were transferred to CRC mice by enema. The vastly disordered gut microbiota of CRC mice was largely reversed by FMT. Intestinal microbiota from normal mice effectively suppressed cancer progression as assessed by measuring the diameter and number of cancerous foci and significantly prolonged survival of the CRC mice. In the intestine of mice that had received FMT, there were massive infiltration of immune cells, including CD8+ T and CD49b+ NK, which is able to directly kill cancer cells. Moreover, the accumulation of immunosuppressive cells, Foxp3+ Treg cells, seen in the CRC mice was much reduced after FMT. Additionally, FMT regulated the expressions of inflammatory cytokines in CRC mice, including down-regulation of IL1a, IL6, IL12a, IL12b, IL17a, and elevation of IL10. These cytokines were positively correlated with Azospirillum_sp._47_25, Clostridium_sensu_stricto_1, the E. coli complex, Akkermansia, Turicibacter, and negatively correlated with Muribaculum, Anaeroplasma, Candidatus_Arthromitus, and Candidatus Saccharimonas. Furthermore, the repressed expressions of TGFb, STAT3 and elevated expressions of TNFa, IFNg, CXCR4 together promoted the anti-cancer efficacy. Their expressions were positively correlated with Odoribacter, Lachnospiraceae-UCG-006, Desulfovibrio, and negatively correlated with Alloprevotella, Ruminococcaceae UCG-014, Ruminiclostridium, Prevotellaceae UCG-001 and Oscillibacter. Our studies indicate that FMT inhibits the development of CRC by reversing gut microbial disorder, ameliorating excessive intestinal inflammation and cooperating with anti-cancer immune responses.

Examination of the emerging role of transporters in the assessment of nephrotoxicity.

INTRODUCTION: The kidney is vulnerable to various injuries based on its function in the elimination of many xenobiotics, endogenous substances and metabolites. Since transporters are critical for the renal elimination of those substances, it is urgent to understand the emerging role of transporters in nephrotoxicity. AREAS COVERED: This review summarizes the contribution of major renal transporters to nephrotoxicity induced by some drugs or toxins; addresses the role of transporter-mediated endogenous metabolic disturbances in nephrotoxicity; and discusses the advantages and disadvantages of in vitro models based on transporter expression and function. EXPERT OPINION: Due to the crucial role of transporters in the renal disposition of xenobiotics and endogenous substances, it is necessary to further elucidate their renal transport mechanisms and pay more attention to the underlying relationship between the transport of endogenous substances and nephrotoxicity. Considering the species differences in the expression and function of transporters, and the low expression of transporters in general cell models, in vitro humanized models, such as humanized 3D organoids, shows significant promise in nephrotoxicity prediction and mechanism study.

BMPR IA downstream genes related to VSD.

Cardiac-specific deletion of the receptor IA of bone morphogenetic protein (BMP) (ALK3) by Cre recombinase driven under the [alpha]-MHC promoter is lethal in mid-gestation with defects in the interventricular septum [ventricular septum defect (VSD)]. Analysis of expression of the ALK3 downstream genes is important to identify the signaling pathway for interventricular septum development. The mRNA expression level of a control group was compared with that of a test group. ALK3 downstream genes were screened using polymerase chain reaction (PCR)-select cDNA subtraction and microarray. It was found that the mice with an ALK3 knockout gene produced a VSD. The expression of some genes such as platelet-activating factor acetylhydrolase (PAF) and Pax-8 was down-regulated in the test group. Pax-8 gene expression was down-regulated by 7.1 times in the test group and expressed specifically in the 11.5-d embryonic (E11.5) heart. Furthermore, the expression of the protein-tyrosine kinase of the focal adhesion kinase subfamily (PTK) and [beta] subtype protein 14-3-3 was up-regulated in the test group. PTK gene expression was up-regulated by 3.7 times in the test group. These data provided support that the ALK3 gene plays an important role during heart development. The PAF and Pax-8 genes could be important ALK3 downstream genes in the BMP signaling pathway during interventricular septum development. PTK and [beta] subtype protein 14-3-3 might be regulatory factors in this pathway.