Oct-2 Protein Expression Research Articles

Farnesoid X Receptor Activation Stimulates Organic Cations Transport in Human Renal Proximal Tubular Cells.

Farnesoid X receptor (FXR) is a ligand-activated transcription factor highly expressed in the liver and kidneys. Activation of FXR decreases organic cation transporter (OCT) 1-mediated clearance of organic cation compounds in hepatocytes. The present study investigated FXR regulation of renal clearance of organic cations by OCT2 modulation and multidrug and toxin extrusion proteins (MATEs). The role of FXR in OCT2 and MATEs functions was investigated by monitoring the flux of 3H–MPP+, a substrate of OCT2 and MATEs. FXR agonists chenodeoxycholic acid (CDCA) and GW4064 stimulated OCT2-mediated 3H–MPP+ uptake in human renal proximal tubular cells (RPTEC/TERT1 cells) and OCT2-CHO-K1 cells. The stimulatory effect of CDCA (20 µM) was abolished by an FXR antagonist, Z-guggulsterone, indicating an FXR-dependent mechanism. CDCA increased OCT2 transport activity via an increased maximal transport rate of MPP+. Additionally, 24 h CDCA treatment increased MATEs-mediated 3H-MPP+ uptake. Moreover, CDCA treatment increased the expression of OCT2, MATE1, and MATE2-K mRNA compared with that of the control. OCT2 protein expression was also increased following CDCA treatment. FXR activation stimulates renal OCT2- and MATE1/2-K-mediated cation transports in proximal tubules, demonstrating that FXR plays a role in the regulation of OCT2 and MATEs in renal proximal tubular cells.

Key role of organic cation transporter 2 for the nephrotoxicity effect of triptolide in rheumatoid arthritis

Tripterygium wilfordii Hook. F. (TwHF), a traditional Chinese Medicine, is effective in treating rheumatoid arthritis (RA), but its severe nephrotoxicity limits its extensive application. The nephrotoxic mechanism of Triptolide (TP), the main pharmacological and toxic component of TwHF, has not been fully revealed. This study was designed to explore the nephrotoxicity of TP in the RA state and the potential molecular mechanism. A rat collagen-induced arthritis (CIA) model was constructed and administered with TP for 28 days in vivo. Results showed that the kidney injury induced by TP was aggravated in the CIA state, the concentration of TP in the renal cortex was higher than that of the medulla after TP administration in the CIA rats, and the expression of organic cation transporter 2 (Oct2) in kidney was up-regulated under CIA condition. Besides, rat kidney slice study demonstrated that TP was transported by Oct2 and this was confirmed by transient silencing and overexpression of OCT2 in HEK-293T cells. Furthermore, cytoinflammatory models on HK-2 and HEK-293T cell lines were constructed by exposure of TNF-α or IL-1β to further explore the TP’s renal toxicity. Results suggested that TNF-α exposure aggravated TP’s toxicity and up-regulated the protein expression of OCT2 in both cell lines. TNF-α treatment also increased the function of OCT2 and finally OCT2 silencing confirmed OCT2 mediated nephrotoxicity of TP in HEK-293T cells. In summary, the exposure of TNF-α in RA state induced the expression of OCT2, which transported more TP into kidney cortex, subsequently exacerbated the kidney injury.

A novel in vivo adjuvant activity of kaempferol: enhanced Tbx-21, GATA-3 expression and peritoneal CD11c+MHCII+ dendritic cell infiltration

Objective: Kaempferol, a natural flavonol present in various traditional medicinal plants, is known to possess potent anti-inflammatory properties. This study was designed to study the adjuvant effect of kaempferol administration along with ovalbumin antigen (K + O) in balb/c mice.Methods: Mice were immunized with kaempferol (100 and 50 mg/kg body weight) without or with ovalbumin (20 µg/mouse). After priming, booster was administered on day 21. Antigen specific IgG titers and its subtypes, on day 28, were estimated by indirect ELISA. Effect of kaempferol administration on CD11c+MHCII+ peritoneal dendritic cells was studied by flow cytometry. Expression levels of proteins Tbx21, GATA-3, BLIMP-1, Caspase-1 and Oct-2 were studied by western blotting. LPS activated IL-1β production by peritoneal cells of immunized mice was estimated by sandwich ELISA.Results: Ovalbumin specific IgG, IgG1 and IgG2a antibody titers in sera samples of K + O immunized mice increased significantly (p < .01) as compared to controls. The enhanced Th1 and Th2 immune response in K + O immunized mice was also supported by the increased expression of Tbx21 and GATA-3 transcription factors in splenocytes. This corroborated with increased BLIMP-1 and Oct-2 protein expression. Kaempferol increased the infiltration of peritoneal CD11c+MHCII+ dendritic cells but failed to enhance LPS activated IL-1β by peritoneal macrophages and suppressed caspase-1 protein expression as compared to that in ovalbumin immunized mice.Conclusion: Present study strongly demonstrates the novel adjuvant activity of kaempferol in vivo and its potential as an immunostimulatory agent.

Inhibitory effect of a callophycin A derivative on iNOS expression via inhibition of Akt in lipopolysaccharide-stimulated RAW 264.7 cells.

In previous studies, (R)-2-isobutyl 3-methyl 3,4-dihydro-1H-pyrido[3,4-b]indole-2,3(9H)-dicarboxylate (1), a callophycin A derivative, was found to strongly inhibit nitrite production in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells, while (R)- or (S)-callophycin A showed only weak inhibition. We currently report additional studies to define the mechanisms underlying the inhibitory action of 1. Expression of inducible nitric oxide synthase (iNOS) was reduced at both protein and mRNA levels. Major upstream signaling molecules and transcription factors regulating iNOS expression were examined, but it was found that 1 did not affect the phosphorylated and total protein levels of p38 mitogen-activated protein kinase (p38 MAPK), Jun N-terminal kinase (JNK), extracellular signal-regulated kinase 1/2 (ERK1/2), and signal transducer and activator of transcription 1 (STAT1), nor did it mediate the degradation of the inhibitor of nuclear factor-κB α-isoform (IκBα). However, starting at early time points, 1 consistently inhibited the phosphorylation of protein kinase B/Akt at serine 473. In addition, 1 suppressed the protein expression of octamer-binding transcription factor-2 (Oct-2) and the expression of microRNA 155 (miR-155). In sum, compound 1 inhibits LPS-induced nitrite production by a unique and complex mechanism. Reduction of iNOS expression is accompanied by inhibition of Akt activation, Oct-2 protein expression, and miR-155 expression.

The B-Cell Specific Transcription Factor, Oct-2, Promotes Epstein-Barr Virus Latency by Inhibiting the Viral Immediate-Early Protein, BZLF1

The Epstein-Barr virus (EBV) latent-lytic switch is mediated by the BZLF1 immediate-early protein. EBV is normally latent in memory B cells, but cellular factors which promote viral latency specifically in B cells have not been identified. In this report, we demonstrate that the B-cell specific transcription factor, Oct-2, inhibits the function of the viral immediate-early protein, BZLF1, and prevents lytic viral reactivation. Co-transfected Oct-2 reduces the ability of BZLF1 to activate lytic gene expression in two different latently infected nasopharyngeal carcinoma cell lines. Furthermore, Oct-2 inhibits BZLF1 activation of lytic EBV promoters in reporter gene assays, and attenuates BZLF1 binding to lytic viral promoters in vivo. Oct-2 interacts directly with BZLF1, and this interaction requires the DNA-binding/dimerization domain of BZLF1 and the POU domain of Oct-2. An Oct-2 mutant (Δ262–302) deficient for interaction with BZLF1 is unable to inhibit BZLF1-mediated lytic reactivation. However, an Oct-2 mutant defective for DNA-binding (Q221A) retains the ability to inhibit BZLF1 transcriptional effects and DNA-binding. Importantly, shRNA-mediated knockdown of endogenous Oct-2 expression in several EBV-positive Burkitt lymphoma and lymphoblastoid cell lines increases the level of lytic EBV gene expression, while decreasing EBNA1 expression. Moreover, treatments which induce EBV lytic reactivation, such as anti-IgG cross-linking and chemical inducers, also decrease the level of Oct-2 protein expression at the transcriptional level. We conclude that Oct-2 potentiates establishment of EBV latency in B cells.

Expression and prognostic significance of Oct2 and Bob1 in multiple myeloma: implications for targeted therapeutics

The B/plasma cell transcription factor Oct2 and its co-activator Bob1 activate the immunoglobulin heavy chain (IgH) gene enhancer. IgH translocations occur in the majority of myeloma cases, leading to overexpression of genes juxtaposed to the IgH enhancers. We hypothesized that Oct2 and Bob1 are determinants of disease behavior and potential therapeutic targets in myeloma. Oct2 and Bob1 gene expressions were measured in CD138+ plasma cells and CD138− cells from bone marrow samples from patients with myeloma (n = 37); gene expression of Oct2 and Bob1 was higher in CD138+ than in CD138− cells (p < 0.0001). Oct2 and Bob1 protein expressions were assessed in bone marrow tissue microarrays from patients with myeloma (n = 169) with fluorescent immunohistochemistry, and correlated to patient survival. High Oct2 protein expression correlated with reduced survival (hazard ratio [HR] 1.74, 95% confidence interval [CI] 1.11–2.73, p = 0.0164), whereas high Bob1 protein expression correlated with increased survival (HR 0.46, 95% CI 0.29–0.71, p = 0.0008). Oct2 should be explored as a potential selective therapeutic target in myeloma.

High Oct-2 Protein Expression Is Associated with Decreased Overall Survival, While High Bob-1 Protein Expression Is Associated with Improved Overall Survival in Myeloma Patients.

Abstract 2822Poster Board II-798 Background:Oct-2 and Bob1 are B-lymphoid lineage specific transcription factors which drive the expression of genes involved in B-lymphocyte and plasma cell development and differentiation, including the immunoglobulin heavy chain (IgH) genes and many others. It is also thought that these transcription factors drive the overexpression of oncogenes involved in IgH translocations through upregulation of the IgH enhancers. We sought to evaluate the expression of Oct-2 and Bob1 in multiple myeloma, a malignancy of the B cell/plasmacyte lineage, in order to determine their potential biological significance as determinants of disease behaviour/prognosis and as potential therapeutic targets. Methods:A tissue microarray containing triplicate samples from 220 myeloma patient samples was generated. Samples were collected at the time of diagnosis between 1993 and 2008. To measure Oct-2 and Bob-1 protein expression in the CD138+ plasma cells of each sample, fluorescent immunohistochemistry was used to stain the samples and the HistoRx PM-2000 platformTM was used to generate an AQUA score for each patient. Oct-2 AQUA scores were available for 169 patient samples and Bob-1 AQUA scores were available for 169 patient samples. The analysis was repeated using conventional immunohistochemistry and visual scoring of staining intensity. Results:The Oct-2 and Bob-1 AQUA scores were continuously distributed over the patient cohort; thus, subsequent analyses were done by dividing the patient cohort by the median Oct-2 or Bob-1 AQUA score and comparing the group with high AQUA scores to the group with low AQUA scores. The patient group with high Oct-2 AQUA scores had an OS of 52.8 months compared to 73.1 months in the group with low Oct-2 AQUA scores (hazard ratio [HR]=1.74, 95% confidence interval [CI]=1.11-2.73, p=0.0164). The patient group with high Bob-1 AQUA scores had an OS of 70.5 months compared with 38.3 months in the group with low Bob-1 AQUA scores (HR=0.46, 95% CI=0.29-0.71, p=0.0008). In a Cox regression proportional hazards model including autologous stem cell transplant (ASCT) status, serum albumin, serum β2-microglobulin and Oct-2 or Bob-1 AQUA scores, only ASCT status was independently predictive of OS. The patient group with low Oct-2 AQUA scores had a significantly higher proportion of ASCT recipients than the group with high Oct-2 AQUA scores. Conversely, the patient group with high Bob-1 AQUA scores had a significantly higher proportion of ASCT recipients than the group with low Bob-1 AQUA scores. Results were similar but not statistically significant when analyzing the TMA with conventional immunohistochemistry and visual scoring of staining intensity. Discussion:In this retrospective study high Oct-2 expression was found to be associated with decreased OS, while high Bob-1 protein expression was associated with increased OS. These results suggest that Oct-2 is a negative prognostic factor in myeloma, while Bob-1 is a favorable prognostic factor, and demonstrates the applicability of the HistoRx platform to myeloma bone marrow TMA analysis. Since this was a small, exploratory study these results must be interpreted with caution and must be confirmed in a larger, prospective analysis. Disclosures:No relevant conflicts of interest to declare.

Organic Cation Uptake Is Enhanced in bcrp1-Transfected MDCKII Cells

Stably transfected cell models are routinely used to examine drug-transporter interactions. In one such model of bcrp1-transfected MDCKII cells, we observed a significant enhancement of organic cation intracellular accumulation. Therefore, our goal was to further explore the expression and functional consequences of this cation transport system. Transport assays were carried out in wild-type and bcrp1-transfected MDCKII cells to examine uptake of [3H]-prazosin (bcrp1 positive control), [3H]-agmatine, [3H]-TEA, and [14C]-choline. RT-PCR was employed to determine the mRNA levels of bcrp1 and OCT2/OCT3. Western blots were used to evaluate corresponding protein levels. Accumulation studies determined a significant increase in the uptake of the organic cations agmatine, TEA, and choline in bcrp1-transfected cells when compared to wild-type cells. Directional transport of [3H]-agmatine showed a significantly greater apical (A) to basolateral (B) than B-to-A flux in both cell types. In spite of this, the A-to-B flux was significantly lower in bcrp1-transfected cells. RT-PCR revealed 10-fold higher OCT2 mRNA levels in bcrp1-transfected cells, with no changes in OCT3. OCT2 protein expression was approximately 3.5-fold higher in bcrp1-transfected cells. The upregulation of OCT2 in bcrp1-transfected MDCKII cells contributed to a significant enhancement in the uptake of several organic cations. These results are consistent with the endogenous expression of OCT2 in the kidney tubule, and may be related to the expression and function of bcrp1. Our findings illustrate the importance of understanding how endogenous transporters, which may compete for common substrates, may be influenced by the overexpression and enhanced function of recombinant transport systems.

Nitric oxide down-regulates the expression of organic cation transporters (OCT) 1 and 2 in rat kidney during endotoxemia

In the kidney, P-glycoprotein (Abcb1), an ATP-driven drug efflux pump, plays an important role in the detoxification of proximal tubule cells through the excretion of cationic and amphipathic organic compounds. We recently found that NO, produced by renal inducible NO synthase (iNOS), is involved in an up-regulation of P-glycoprotein during endotoxemia in rats. In the present study, we investigated the functional consequences of endotoxemia on the renal handling of rhodamine 123 by using isolated perfused rat kidneys. Wistar Hannover rats were injected intraperitoneally with 5 mg/kg body weight lipopolysaccharide (LPS) or with both LPS and the iNOS inhibitor, aminoguanidine. Despite an increased P-glycoprotein expression, we found a diminished urinary rhodamine 123 clearance 12 h after LPS (P<0.001). In addition, we found a diminished perfusate clearance (P<0.05) for rhodamine 123 after LPS treatment, suggesting a predominant role of influx carriers in urinary rhodamine 123 excretion. We examined the expression levels of organic cation transporter 1 (Slc22a1/Oct1) and Slc22a2/Oct2. Both appeared to be down-regulated at the mRNA and protein level, 12 h after LPS. Co-administration of aminoguanidine attenuated the down-regulation of both Oct1 and Oct2 protein expression and reversed the decrease in rhodamine 123 clearance (P<0.001). These findings indicate that NO, produced by iNOS, is responsible for a down-regulation of the influx carriers, Oct1 and Oct2.

Expression of Oct2 and its significance in lymphoma diagnosis

To investigate the specificity and sensitivity of Oct2 protein expression in lymphoma cells and its significance in diagnosis and classification of lymphoma. Formalin-fixed and paraffin-embedded materials from 129 cases of lymphoma and 10 cases of reactive lymphoid hyperplasia (RLH) were studied by EnVision immunohistochemistry for Oct2 protein. Oct2 was mainly expressed in germinal center cells of RLH. It was diffusely expressed in B-cell lymphoma cells. 97.7% cases (85/87) of B-cell lymphoma and 3.8% cases (1/26) of T-cell lymphoma were positive for Oct2 protein. In comparison, the expression rates for CD20 and CD79alpha in B-cell lymphomas were 90.8% (79/87) and 84.7% (61/72) respectively. The difference in expression rates between Oct2 protein and CD20 was not statistically significant (P > 0.05) There was, however, significant difference in expression rates between Oct2 protein and CD79alpha (P < 0.05). The expression rates of Oct2 protein in nodular lymphocyte-predominant Hodgkin lymphoma and classic Hodgkin lymphoma were 3/3 and 46.2% (6/13) respectively. The difference in expression rates of Oct2 protein in these two groups showed no statistical significance (P > 0.05). As a relatively sensitive and specific marker for B cells, Oct2 can serve as a useful antibody for the diagnosis and differential diagnosis of lymphoma.