Dysregulation of renal transporters in a rodent model of viral Infection.

Inflammation elicited by viral mimetic poly I:C has been shown to impose changes in the expression of drug transporters in the placenta and maternal liver in rats at term pregnancy. This was associated with altered drug disposition in the mother and fetus. Renal transporters play an important role in the elimination of several drugs taken by pregnant women. We examined the impact of poly I:C on the expression of renal transporters in pregnant rats at term. Pregnant Sprague-Dawley rats received single intraperitoneal dose of either poly I:C (5 mg/kg) or saline at gestation day 18 (n = 8/group). Animals were euthanized 24 h after the injection. The mRNA and protein expression of pro-inflammatory cytokines and transporters were measured by qRT-PCR and western blot. Poly I:C caused a fourfold increase in the mRNA of IL-6 in the kidney. As compared to saline controls, the mRNA expression of Mrp2, Bcrp, Octn1, Oat1, Oat2, Oat3, Urat1, Oatp4c1, and Pept2 was downregulated, whereas the Ent1 mRNA was increased. Protein expression of Bcrp, Urat1 and Pept2 were significantly decreased. While there was a trend towards reduced Mrp2, Oat2 and Oat3 protein expression, this did not reach significance. Poly I:C did not impact mRNA levels of Mdr1a, Mdr1b, Mrp4, Oct1, Oct2, Oct3, Octn2, Mate1, Ent2 or Pept1. Viral-induced inflammation mediates significant changes in the expression of several key drug transporters in the kidney of pregnant rats. Many clinically important drugs are substrates for these transporters. Therefore, inflammation-mediated alterations in transporter expression could affect their maternal and fetal disposition.

Impact of Viral Inflammation on the Expression of Renal Drug Transporters in Pregnant Rats.

Inflammation impacts the expression and function of drug transporters at term-gestation; however, the impact of inflammation on the expression of drug transporters at mid-gestation is largely unknown. Since renal drug transporters play a key role in the clearance of many drugs prescribed during pregnancy, our objective was to study the impact of the viral mimetic poly I:C on the expression of renal transporters in pregnant rats at mid-gestation. Poly I:C (10 mg/kg) or saline was administered intraperitoneally to pregnant Sprague-Dawley rats on gestational day 14. Expression of renal transporters was measured at 6, 24, and 48 h by qRT-PCR and Western blot. The mRNA levels of Mdr1a, Mrp4, Oct2, Octn1, Octn2, Mate1, Oat1-3, Urat1, Oatp4c1, Ent1, and Pept2 were significantly lower in the poly I:C group at 6 h. At 24 h, only the mRNA levels of Oct2, Oatp4c1, and Ent1 were decreased compared to saline. Poly I:C significantly decreased protein expression of Urat1 at 24 h, and P-gp, Oct2, Mate1, Oat1, Oat3 at 48 h,. Poly I:C imposed significant reductions in the expression of several key renal transporters at mid-gestation in pregnant rats. Thus, viral infection may impact renal excretion of drug transporter substrates, potentially leading to drug-disease interactions.

Endotoxin Modulates the Expression of Renal Drug Transporters in HIV-1 Transgenic Rats.

PURPUSE: Bacterial co-infections and low grade endotoxemia are common in HIV patients. Inflammation due to endotoxin or HIV may influence the expression and activity of transporters. Kidney transporters influence renal drug clearances including many antiretroviral agents. Our objective was to study the effect of endotoxin and HIV on the renal expression of drug transporters in an HIV-transgenic (HIV-Tg) rat model. These rats develop immune dysfunction and AIDS-associated conditions like humans. METHODS: Endotoxin or saline was administered intraperitoneally to HIV-Tg or wild type (WT) littermates and kidneys were collected 18 hours later. Expression of transporters and cytokines were measured by qRT-PCR and Western blots. Serum cytokine levels were measured by ELISA. RESULTS: Endotoxin induced serum levels of IL-6, TNF-α and IFN-γ in both HIV-Tg and WT animals. The basal mRNA expression of Oct2, Oct3, Octn1, Mate1, Urat1 and Ent1was significantly lower (33-60%) and the expression of Ent2 and Pept2 was significantly higher (33-45%) in HIV-Tg as compared to WT. While endotoxin significantly downregulated the mRNA expression of Mdra1 and Pept2 in both HIV and WT groups (69-78%), it imposed a significant reduction on the mRNA expression of Oct2, Oct3, Octn1, Mate1, Oat2, urat1, and Ent1 (54-83%) only in the WT group. Endotoxin significantly increased the mRNA expression of Pept1 (140%) in both WT and HIV groups. CONCLUSIONS: HIV and endotoxin each imposed alterations in the expression of many clinically important renal drug transporters although co-infection did not augment this effect. Viral and/or bacterial infections may impact the renal clearance of drug substrates in patients and could potentially be a source of drug-disease interactions.

Insulin silences apolipoprotein B mRNA translation by inducing intracellular traffic into cytoplasmic RNA granules.

Insulin is a potent inducer of global mRNA translation and protein synthesis, yet it negatively regulates apolipoprotein B (apoB) mRNA translation, via an unknown mechanism. ApoB mRNA has a long half-life of 16 h, suggesting intracellular storage as mRNPs likely in the form of RNA granules. The availability of apoB mRNA for translation may be regulated by the rate of release from translationally silenced mRNPs within cytoplasmic foci called processing bodies (P bodies). In this report, we directly imaged intracellular apoB mRNA traffic and determined whether insulin silences apoB mRNA translation by entering cytoplasmic P bodies. We assessed the colocalization of apoB mRNA and ß-globin mRNA (as a control) with P body (PB) markers using a strong interaction between the bacteriophage capsid protein MS2 and a sequence specific RNA stem-loop structure. We observed statistically significant increases in the localization of apoB mRNA into P bodies 4-16 h after insulin treatment (by 72-89%). The movement of apoB mRNA into cytoplasmic P bodies correlated with reduced translational efficiency as assessed by polysomal profiling and measurement of apoB mRNA abundance. PB localization of ß-globin mRNA was insensitive to insulin treatment, suggesting selective regulation of apoB mRNA by insulin. Overall, our data suggest that insulin may specifically silence apoB mRNA translation by reprogramming its mRNA into P bodies and reducing the size of translationally competent mRNA pools. Translational control via traffic into cytoplasmic RNA granules may be an important mechanism for controlling the rate of apoB synthesis and hepatic lipoprotein production.