Rat Retinal Vascular Endothelial Cells Research Articles

Comparative analysis of co-culture and monoculture models in simulating diabetic neurovascular dysfunction: insights into diabetic retinopathy.

Interaction between retinal vascular endothelial cells and neurons plays a critical role in the pathogenesis of diabetic retinopathy (DR). This study aims to compare an in vitro model over a monoculture model to simulate the neurovascular coupling under the hyperglycemic microenvironment of diabetes. Rat retinal vascular endothelial cells (RRMECs) and ganglion cells (RGCs) were seeded mono- or co-cultured in a normal (NG, 5.5 mM) and high (HG, 75 mM) glucose concentrations culture medium. Cell viability was detected by the cell counting kit-8 (CCK-8) assay. The ability of migration and lumen formation of RRMECs were determined by scratch wound, transwell migration, and lumen formation assays. The apoptosis index of cells was calculated and detected by propidium iodide (PI)/Hoechst staining. Quantitative and morphological analysis of RGCs was performed through the labeling of RGCs by brain-specific homeobox/POU domain protein 3A (BRN3A) and anti-beta-III tubulin (TUJ1). The gene and protein expression levels of occludin (OCLN) and zonula occludens-1 (ZO-1) were evaluated by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay. The viability, migration, and lumen formation abilities of RRMECs in the HG group significantly increased (P<0.05) in both mono- and co-culture models. Migration and lumen formation abilities of RRMECs in the co-culture with HG were lower than that in the monoculture group (P<0.05). The viability of RGCs cells with HG significantly decreased in both mono- and co-culture models (Pmono<0.001, Pco<0.001), the apoptosis index of RGCs in the co-culture with HG was higher than that in the monoculture (P=0.010). The protein and gene expression of OCLN, and ZO-1 in RRMECs significantly decreased with HG culture medium in both culture models (P<0.05). In the HG group, the protein and gene expression level of the ZO-1 and OCLN of RRMECs significantly decreased in the co-culture model than that in the monoculture model (P<0.05). Compared with mono cell culture, the established co-culture in vitro system for diabetic neurovascular dysfunction can better stimulate the micro-environment of the retinal neurovascular unit.

Identification and Validation of Genes Related to RNA Methylation Modification in Diabetic Retinopathy

Purpose To identify and validate the differentially expressed genes related to RNA methylation modification in diabetic retinopathy. Methods The data sets GSE12610 and GSE111465 related to diabetic retinopathy in the Gene Expression Omnibus were selected. The R software package was used to identify differentially expressed genes related to RNA methylation modification in diabetic retinopathy. Protein-protein interaction network was constructed to explore the interactions between proteins and predict proteins. Then, Gene Ontology annotation analysis and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis were used to analyze the potential enrichment pathways and clarify the biological functions of these genes. In addition, the correlation between them and immune cells was visualized, and receiver operating characteristic curves were drawn to evaluate the diagnostic performance of each one of them for diabetic retinopathy. To verify the differentially expressed genes, the mRNA expression of rat retinal vascular endothelial cells cultured in low and high glucose medium separately were detected by RT-qPCR. Results The expression of Lrpprc, Nsun4, Nsun6 and Trdmt1 were significantly up-regulated in diabetic retinopathy samples, while the expression of Cbll1, Hnrnpc, Mettl3 and Wtap were significantly down-regulated. Differentially expressed genes were mainly enriched in the RNA-methylation-medication pathways and biological function. The results of immune infiltration analysis proved that eosinophils aggregated more in diabetic group, while T cells follicular helper aggregated more in normal samples. These genes of Cbll1 (AUC = 0.986), Hnrnpc (AUC = 0.819), Lrpprc (AUC = 0.806), Mettl3 (AUC = 0.917), Nsun4 (AUC = 0.819), Nsun6 (AUC = 0.819), Trdmt1 (AUC = 0.972) and Wtap (AUC = 0.972) were respectively used as the diagnostic basis of diabetic retinopathy. According to the RT-qPCR results, the expression of Mettl3 was significantly down-regulated (p < 0.0005) in cells cultured in high glucose, while Trdmt1 (p < 0.05), Nsun4 (p < 0.05) and Nsun6 (p < 0.05) were significantly up-regulated. Conclusion Differentially expressed genes such as Mettl3, Nsun4, Nsun6, and Trdmt1 should be conducted to explore, and the role of RNA methylation in the process of diabetic retinopathy would be revealed in-depth.

Curcumin suppresses oxidative stress via regulation of ROS/NF-κB signaling pathway to protect retinal vascular endothelial cell in diabetic retinopathy

BackgroundThe retinal vascular endothelial cells can be damaged by oxidative stress even in the early stage of diabetic retinopathy (DR). This study aimed to investigate the protective effect of curcumin on the rat retinal vascular endothelial cells (RRVECs) in high glucose circumstance.ObjectiveThe cultured RRVECs were identified and characterized by both of vWF and CD31 immunofluorescence expression. The activation of ROS/NF-κB signal pathway was examined by electrophoretic Mobility Shift Assay (EMSA), immunohistochemistry and Western blot; the apoptosis of RRVECs was tested by flow cytometry.ResultsWe found that curcumin reduced the reactive oxygen species (ROS) and relieved the apoptosis in RRVECs exposed to the high glucose by flow cytometry. It was revealed that the increased activity of NF-κB and phosphorylated NF-κB in RRVECs induced by high glucose concentration was significantly suppressed by curcumin.ConclusionWe concluded that curcumin could suppress the oxidative stress via regulation of NF-κB signal to protect the RRVECs in DR.

MicroRNA-34a promotes apoptosis of retinal vascular endothelial cells by targeting SIRT1 in rats with diabetic retinopathy

ABSTRACT MiR-34a is associated with diabetic retinopathy (DR). This article aims to demystify the role of miR-34a in DR. We established a DR model by streptozocin injection. Rat retinal vascular endothelial cells (RVECs) were treated with high glucose (HG) to induce DR. The pathological changes of retinal tissues and blood-retinal vascular barrier permeability of DR rats were assessed by HE staining and Evans-Blue leak test. The expression of gene and protein was evaluated by quantitative real-time PCR or western blot. MTT assay and flow cytometry were performed to detect proliferation and apoptosis. The relationship between miR-34a and SIRT1 was evaluated using luciferase reporter assay. MiR-34a was up-regulated and SIRT1 was down-regulated in retinal tissues of DR rats and HG-induced RVECs. MiR-34a silencing improved DR by regulating apoptosis and VEGF expression in DR rats. Furthermore, miR-34a interacted with SIRT1 and suppressed SIRT1 expression. MiR-34a overexpression inhibited proliferation and promoted apoptosis of RVECs, which was effectively abolished by SIRT1 up-regulation. In summary, our data demonstrate that miR-34a promotes apoptosis of RVECs by targeting SIRT1 in DR rats. Our findings suggest that miR-34a/SIRT1 axis could be a valuable target for DR therapies.

Hyperoside Ameliorates Diabetic Retinopathy via Anti-Oxidation, Inhibiting Cell Damage and Apoptosis Induced by High Glucose.

BackgroundHyperoside (Hyp) is a flavonoid substance extracted from plants, which has the functions of anti-cancer, anti-inflammatory, and anti-oxidation. In the previous study, we found that Hyp reduced the injury of rat retinal vascular endothelial cells (RVECs) induced by H2O2.MethodIn the present research, we evaluated the protective effect of Hyp on the pathological damage of retina caused by high glucose of diabetes mellitus (DM) in in vitro and in vivo experiments. The effect of Hyp on cell viability, oxidative stress level, and apoptosis of RVECs was assessed.ResultsHyp significantly reduced the of RVECs damage, oxidative stress level, and cell apoptosis induced by high glucose in vitro. In DM model rats, Hyp treatment could significantly reduce blood glucose levels and the pathological damage of retina caused by DM and increase the proliferation of RVECs while exerting the inhibition on apoptotic activity. Furthermore, Hyp treatment decreased the expressions of apoptotic proteins including caspase-3, caspase-9, and Bax in RVECs of DM rats, while increased the expression of anti-apoptotic protein Bcl-2.ConclusionHyp may have protective effect on diabetes-induced retinopathy by reducing oxidative stress, inhibiting cell damage, and apoptosis induced by high glucose.

The effects of Curcumin on the cellular apoptosis induced by high glucose in rat retinal vascular endothelial cells

Objective To observe the effects of Curcumin on the cellular apoptosis of rat retinal vascular endothelial cells (RRVEC) induced by high glucose. Methods Generation 4 cultured RRVEC were used in this experiment, and identified with anti-vWF factor antibody by immunochemistry and immunofluorescence. The RRVEC were divided into control group (5.5 mmol/L glucose), high glucose group (30 mmol/L glucose), and treatment group (30 mmol/L glucose+30 μmol/L Curcumin), respectively. Flow cytometry was used to measure the cellular reactive oxygen species (ROS) level and apoptosis. The expression intensity and location of nuclear factor (NF)-κB p65 in the cells of the three groups were detected by immunochemistory. The expression of Bcl-2 and Bax protein was detected by Western blot test. Results Immunostaining showed that RRVEC were positive for vWF factor. The flow cytometry showed that the cellular ROS level in treatment group was higher than that in the control group (t=8.677, P=0.000), but less than that in the high glucose group (t=40.957, P=0.000). Compared with the high glucose group, the cellular ROS level in the treatment group was decreased significantly (t=6.568, P=0.000). The cellular apoptosis were significantly different among the three groups (F=325.137, P=0.000). Compared with the high glucose group, the cellular apoptosis in the treatment group was decreased significantly (t=12.818, P=0.000). Immunochemistry showed that NF-κB p65 was expressed strongly in the cellular nuclei and cytoplasm in the high glucose group than that in the control group and the treatment group with the significant differences (t=8.322, P=0.000). Western blot results demonstrated that compared with the control group, the expression of Bcl-2 of RRVEC and Bcl-2/Bax ratio decreased (t=4.362, 6.449; P=0.005, 0.001) and Bax increased (t=3.813, P=0.009) in the high glucose group, with statistically significant differences. Compared with the high glucose group, the expression of NF-κB and Bax decreased (t=2.577, 3.059; P=0.042, 0.022) and Bcl-2/Bax ratio increased significantly (t=3.831, P=0.009) in the treatment group. Conclusion Curcumin could suppress the cellular apoptosis of RRVEC induced by high glucose. The mechanism of Curcumin protecting RRVEC may be via regulating NF-κB signal pathway. Key words: Curcumin; Retinal Vessels/pathology; Endothelial cells; Apoptosis; NF-κB

Glucocorticoid-Induced Leucine Zipper Suppresses ICAM-1 and MCP-1 Expression by Dephosphorylation of NF-κB p65 in Retinal Endothelial Cells.

Glucocorticoid-induced leucine zipper (GILZ) is involved in anti-inflammatory activities in several animal models and in various cell types. In this study, we explored the role of GILZ in rat retinal vascular endothelial cells. Glucocorticoid-induced leucine zipper overexpression or silencing was established using GILZ overexpressing recombinant lentivirus (OE-GILZ-rLV) or short-hairpin RNA targeting GILZ recombinant lentivirus (shRNA-GILZ-rLV), respectively, in rat primary retinal microvascular endothelial cells (RMECs) and intact retina. Seventy-two hours after transfection, RMECs were stimulated with 1000 ng/mL lipopolysaccharide (LPS), 20 μM isoliensinine (an alkaloid derived from the embryos of Nelumbo nucifera, could enhance the dephosphorylation of p65 at Ser536), or PBS for another 24 hours. Western blotting and immunofluorescence were performed to measure protein expression. The concentrations of intercellular adhesion molecule (ICAM)-1 and monocyte chemoattractant protein (MCP)-1 in the RMEC culture media were measured by ELISA. Lipopolysaccharide downregulated GILZ expression in RMECs in a time- and dose-dependent manner, and the decrease in GILZ expression was accompanied by increased ICAM-1 and MCP-1 expression. Glucocorticoid-induced leucine zipper overexpression decreased LPS-induced ICAM-1 and MCP-1 expression, whereas GILZ silencing significantly attenuated the production of both cytokines. Glucocorticoid-induced leucine zipper overexpression also inhibited LPS-induced nuclear factor-κB p65 nuclear translocation in RMECs that was mediated by enhanced p65 dephosphorylation. The dephosphorylation of NF-κB p65 further downregulated ICAM-1 and MCP-1 expression in RMECs. Glucocorticoid-induced leucine zipper overexpression inhibited NF-κB p65 nuclear translocation by enhancing p65 dephosphorylation. Exogenous GILZ regulated ICAM-1 and MCP-1 expression, which was probably mediated by enhanced p65 dephosphorylation.

Blood-to-retina transport of biotin via Na +-dependent multivitamin transporter (SMVT) at the inner blood-retinal barrier

The purpose of this study was to elucidate the mechanisms of biotin transport across the inner blood-retinal barrier (inner BRB). [ 3H]Biotin transport in the retina across the inner BRB was examined using an in vivo integration plot and retinal uptake index analyses in rats. The transport mechanism was characterized using a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2 cells) as an in vitro inner BRB model. The apparent influx permeability clearance ( K in) per gram retina of [ 3H]biotin was found to be 5.55 μL/(min g retina). The K in of [ 3H]biotin was 8.9-fold greater than that of [ 3H]D-mannitol, a non-permeable paracellular marker. [ 3H]Biotin uptake by the retina was found to be significantly inhibited by biotin and pantothenic acid, supporting carrier-mediated influx transport of biotin at the inner BRB. [ 3H]Biotin uptake by TR-iBRB2 cells was Na +-, temperature-, and concentration-dependent with a K m of 146 μM. These forms of transport were significantly inhibited by Na +-dependent multivitamin transporter (SMVT) substrates such as biotin, pantothenic acid, lipoic acid, and desthiobiotin. These transport properties are consistent with those of biotin transport by SMVT. SMVT mRNA was expressed in TR-iBRB2 cells and isolated rat retinal vascular endothelial cells. Our findings suggest that SMVT is involved in the transport of biotin from the circulating blood to the retina across the inner BRB.

Cationic amino acid transporter 1‐mediated l‐arginine transport at the inner blood–retinal barrier

The purpose of this study was to identify the transporter mediating l-arginine transport at the inner blood-retinal barrier (BRB). The apparent uptake clearance of [(3)H]L-arginine into the rat retina was found to be 118 microL/(min.g retina), supporting a carrier-mediated influx transport of L-arginine at the BRB. [(3)H]L-arginine uptake by a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2 cells), used as an in vitro model of the inner BRB, was primarily an Na(+)-independent and saturable process with Michaelis-Menten constants of 11.2 microM and 530 microM. This process was inhibited by rat cationic amino acid transporter (CAT) 1-specific small interfering RNA as well as substrates of CATs, L-arginine, L-lysine, and L-ornithine. The expression of cationic amino acid transporter (CAT) 1 mRNA was 25.9- and 796-fold greater than that of CAT3 in TR-iBRB2 and magnetically isolated rat retinal vascular endothelial cells, respectively. The expression of CAT1 protein was detected in TR-iBRB2 cells and immunostaining of CAT1 was observed along the rat retinal capillaries. In conclusion, CAT1 is localized in retinal capillary endothelial cells and at least in part mediates L-arginine transport at the inner BRB. This process seems to be closely involved in visual functions by supplying precursors of biologically important molecules like nitric oxide in the neural retina.

Lysophospholipids enhance taurine release from rat retinal vascular endothelial cells under hypoosmotic stress

Sphingosine 1-phosphate (S1P) and lysophosphatidic acid (LPA) are simple bioactive lysophospholipids which exhibit an effect on blood vessels via their G protein-coupled receptors. The purpose of this study was (i) to clarify the impact of S1P and LPA on the release of taurine as an organic osmolyte from rat retinal vascular endothelial cells (RVECs) under hypoosmotic stress and (ii) to quantify the gene expression levels of S1P and LPA receptors in RVECs. When cultured RVECs (TR-iBRB2 cells) that had been preloaded with [ 3H]taurine were exposed to hypotonic buffer (230 mOsm) for 1 to 10 min, [ 3H]taurine release from the cells was several times greater than that using an isotonic buffer (300 mOsm). S1P and LPA significantly enhanced the [ 3H]taurine release under hypotonic conditions in a time- and concentration-dependent manner, whereas S1P and LPA had no significant effect under isotonic conditions. Quantitative real-time PCR revealed that freshly isolated RVECs predominantly express mRNAs for S1P 1, S1P 4 and LPA 4. The S1P-enhanced [ 3H]taurine release under hypoosmotic conditions was significantly inhibited by an S1P 1 receptor antagonist. Inhibitor of the small GTPase Rho, C3 exotoxin, attenuated S1P- and LPA-enhanced [ 3H]taurine release. These results suggest that S1P and LPA play a novel role in the regulation of osmolyte efflux from RVECs in response to hypoosmotic stress via the activation of their specific receptors.

Involvement of Reduced Folate Carrier 1 in the inner Blood-Retinal Barrier Transport of Methyltetrahydrofolate

The purpose of this study was to elucidate the mechanism of methyltetrahydrofolate (MTF) transport at the inner blood-retinal barrier (inner BRB). The characteristics and function of MTF transport at the inner BRB were examined using a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2) as an in vitro model of the inner BRB. The [3H]MTF uptake by TR-iBRB2 cells increased with lowering extracellular pH and was Na+- and Cl--independent. The [3H]MTF uptake was concentration-dependent with a K(m) of 5.1 microM. This process was inhibited by reduced folate carrier 1 (RFC1) substrates, such as methotrexate and formyltetrahydrofolate, in a concentration-dependent manner with an IC50 of 8.7 and 2.8 microM, respectively, suggesting that RFC1 mediates MTF uptake in TR-iBRB2 cells. Although both RFC1 and proton-coupled folate transporter (PCFT) mRNA, which are pH-sensitive folate transporters, are expressed in TR-iBRB2 cells and isolated rat retinal vascular endothelial cells, the expression level of RFC1 mRNA was 83- and 49-fold greater than that of PCFT, respectively. Taken together, the above findings are consistent with the involvement of RFC1 in the inner BRB transport of MTF.

Dexamethasone intensify the tight junctions in rat retinal vascular endothelial cells in vitro

To investigate the effect of dexamethasone on the expression, distribution and function of tight junctions in rat retinal vascular endothelial cells in vitro. Try to explain the mechanism of glucocorticoid in the treatment of macular edema from a new viewpoint. Rat retinal vascular endothelial cells were isolated and purified by magnetic beads coated with anti-CD31. Cells were identified by vW factor indirect immunofluorescence staining. The fourth-passage cells were used to investigate the effect of dexamethasone on the tight junctions in rat retinal vascular endothelial cells. Cells were separated into two groups, one was treated with 500 nmol/L dexamethasone and the other was used as the control. Transepithelial electrical resistance (TER) was measured to estimate the changes in the treated group. Indirect immunofluorescent stain and RT-PCR were used to observe the difference of tight junction protein distribution and mRNA expression level between these two groups. Rat retinal vascular endothelial cell monolayer showed positive immunofluorescent staining for vW factor. The dexamethasone treated group showed greater TER than that of the control (P < 0.01). Tight junction protein in the dexamethasone treated group localized closer to the borders of retinal vascular endothelial cells than that of the control. Claudin-1 mRNA level of the dexamethasone treated cells were greater than that of the control. Dexamethasone intensifies the tight junctions in rat retinal vascular endothelial cells. Therefore this is one of the mechanisms of treatment of macular edema by glucocorticoid.

L-Type Amino Acid Transporter 1–Mediatedl-Leucine Transport at the Inner Blood–Retinal Barrier

L-type amino acid transporters (LATs) prefer branched-chain and aromatic amino acids, including neurotransmitter precursors. The objective of this study was to clarify the expression and function of LAT at the inner blood-retinal barrier (BRB). [3H]L-Leucine transport at the inner BRB was characterized by using in vivo integration plot analysis and a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2). The expression of the LAT1 was demonstrated by quantitative real-time RT-PCR, immunoblot, and immunohistochemical analyses. The apparent influx permeability clearance of [3H]L-leucine in the rat retina was found to be 203 microL/(min.g retina), supporting a carrier-mediated influx transport of L-leucine at the BRB. [3H]L-Leucine uptake by TR-iBRB2 cells was an Na+-independent and concentration-dependent process with a Km of 14.1 microM. This process was more potently cis inhibited by substrates of LAT1, D-leucine, D-phenylalanine, and D-methionine, than those of LAT2, L-alanine, and L-glutamine. [3H]L-Leucine efflux from TR-iBRB2 cells was trans-stimulated by substrates of LAT1. The expression of LAT1 mRNA was 100- and 15-fold greater than that of LAT2 in TR-iBRB2 and magnetically isolated rat retinal vascular endothelial cells, respectively. The expression of LAT1 protein was observed in TR-iBRB2 and primary cultured human retinal endothelial cells and immunostaining of LAT1 was observed along the rat retinal capillaries. LAT1 is expressed at the inner BRB and mediates blood-to-retina L-leucine transport. This transport system plays a key role in maintaining large neutral amino acids as well as neurotransmitters in the neural retina.

The effect of Toxoplasma gondii infection on expression of chemokines by rat retinal vascular endothelial cells

Cells infected by Toxoplasma gondii undergo up-regulation of proinflammatory cytokines, organelle redistribution, and protection from apoptosis. During infection in man, the parasite encysts within the retina, a process that results in retinochoroiditis which can lead to permanent loss of sight. The reasons for the parasite to infect retinal tissue and the mechanisms by which it encysts are not clearly understood. We studied the effect of infection with T. gondii of retinal vascular endothelial cells using the Clontech Atlas™ array system in order to elucidate changes in gene expression. We compared hybridization of RNA to the array from infected and uninfected cells at two time points; 2 and 24 h. Exposure to T. gondii after 2 h resulted in change of expression of ∼6% of genes on the array, including those involved in cell structure, protein and vesicle trafficking, cell-cycle regulation, transcriptional and translational machinery, and apoptosis. Among the genes involved in the inflammatory response, chemokine genes such as GRO1 ( Growth Regulated Oncogene 1), MCP-1 ( Monocyte Chemotactic Protein- 1), FKN (Fractalkine) and RANTES ( Regulated upon Activation, Normal T Cell Expressed and Secreted) were found to be up-regulated and protein production was confirmed by ELISA. However after 24 h of infection, GRO1, MCP-1 and FKN were down-regulated, confirmed by RT-PCR. Thus, invasion of retinal vascular endothelium (RVE) cells by T. gondii leads to the production of chemokines important in directing the traffic of inflammatory cells to the infected area.

Application of magnetically isolated rat retinal vascular endothelial cells for the determination of transporter gene expression levels at the inner blood–retinal barrier

The purpose of the present study was to quantify transporter gene levels at the inner blood-retinal barrier (inner BRB) using a combination of magnetic isolation method for rat retinal vascular endothelial cells (RVEC) and real-time quantitative PCR analysis. The transcript levels of CD31, Tie-2, claudin-5, occludin, Jam-1, mdr1a, oatp2, and oatp14 in the RVEC fraction were more than 100-fold greater than those in the non-RVEC fraction, suggesting that these genes are predominantly expressed at the inner BRB. The transcript levels of GLUT1 and MCT1 in the RVEC fraction were the most abundant in the respective transporter family, suggesting that GLUT1 and MCT1 play a predominant role in d-glucose and monocarboxylate transport, respectively, at the inner BRB. In conclusion, application of magnetically isolated RVEC is able to determine transporter gene levels at the inner BRB thereby increasing our understanding of inner BRB functions at a molecular level.

The effect of cytokines on the replication of T. gondii within rat retinal vascular endothelial cells

Toxoplasma gondii infection of the eye can result in a recurrent necrotising retinochoroiditis (TR) which may lead to a permanent loss of visual acuity. The mechanisms responsible for the control of TR within the retina are unknown. The aim of this study was to examine the effects of cytokines on the replication of T. gondii RH strain tachyzoites within rat retinal vascular endothelial (rRVE) cells. Pretreatment of rRVE with IFNγ, TNF or IL-1β resulted in a significant decrease in T. gondii replication from day 2 onwards. There was no significant difference in nitric oxide (NO) production by IFNγ, TNF or IL-1β treated rRVE as compared to controls at any time point. By comparison, the addition of l-tryptophan to IFNγ treated cultures significantly restored T. gondii replication from 48 h post inoculation. Thus, IFNγ, TNF and IL-1β can significantly inhibit the replication of T. gondii within rRVE. However, this inhibition appears to be independent of NO production. l-tryptophan catabolism may have a role in IFNγ mediated inhibition of T. gondii replication in rRVE cells.