Abstract P335: Contribution Of The Gut To The Salt-sensitive Phenotype Of Dahl S Rats Is Reflected In Increased Sodium Absorption In The Distal Colon

Salt-sensitive hypertension in Dahl sensitive (Dahl S) rats is primarily attributed to sodium mishandling associated with kidney dysfunction, and very few studies interrogated sodium absorption in the gut of Dahl S rats and its potential contribution to the salt-sensitive phenotype. To assess this, we compared sodium channel (ENaC)-driven sodium (Na + ) currents, as a measure of Na + transport across the distal colon, the primary sodium absorption site in the GI tract, between Dahl S and Dahl salt-resistant (Dahl R) rats ex vivo . In parallel, we evaluated fecal sodium levels to assess overall fecal sodium loss in Dahl S and R rats. Male adult (12-14wo) Dahl S and R were administered a low sodium diet (0.3% NaCl, Teklad) ad libitum from weaning. Prior to the experiment, food intake/rat was measured every day for three consecutive days. On the day of experiment, rats were euthanized by an overdose of isoflurane. Distal colons were dissected and transferred to the Ussing chamber with oxygenated warm Krebs solution containing d-glucose. Increasing concentrations of the ENaC blocker amiloride (0.01-1000uM) were applied to the Ussing chamber on the apical side of the distal colon in 10-minute intervals. Maximum decreases in total ionic current across the distal colon were measured in real time following addition of amiloride to quantify ENaC Na + current across the distal colon. Fecal samples were homogenized in distilled water, and sodium levels per gram of fecal mass were determined by flame photometry. Despite no differences in food intake, we observed a dose-dependent 2 to 4-fold higher responses to amiloride in the distal colon of Dahl S compared to Dahl R rats, suggesting elevated Na + current in the Dahl S. Conversely, a ~2-fold lower Na + concentration was detected in the feces of Dahl S compared to Dahl R rats. In conclusion, elevated ENaC-driven Na + current in the distal colon, coupled with reduced fecal Na + concentration, suggest higher absorption/transport of Na + across the distal colon of Dahl S compared to Dahl R rats, which was independent of salt intake. Considering that the circulating Na + levels are reportedly maintained in the Dahl S by the overworked kidney, elevated colonic sodium absorption may contribute to kidney disease and salt-sensitive phenotype in Dahl S.

Abstract MP54: Pro-resolving Lipid Mediators Ameliorate Endothelium Dysfunction In Arteries From Hypertensive Rats

Resolution of inflammation is an active phenomenon to switch off the inflammatory processes andfacilitate the return to homeostasis. Increasing the levels of pro-resolving lipid mediators topromote the resolution of inflammation is emerging as a novel therapeutic approach. Arachidonicacid (AA) and docosahexaenoic acid (DHA) are substrates to produce the pro-resolving lipidmediators lipoxin A4 (LXA4) and resolvin D1 (RvD1), respectively. However, it is unknown if thesemediators can ameliorate dysfunction in arteries from hypertensive animals. Therefore, wehypothesized that pro-resolving lipid mediators decrease acetylcholine-induced contractions inarteries from spontaneously hypertensive rats (SHR). Mesenteric resistance arteries from maleSHR and Wistar Kyoto (WKY) (14-weeks old, n=6-8) were used for vascular function via wiremyograph. MRA were incubated with either RvD1 or LXA4 (10 nM, 1 hour) or vehicle prior toconcentration response curves to acetylcholine or phenylephrine (1 nM - 3 μM). We alsoperformed lipidomic analysis on plasma from WKY and SHR. As expected, low concentrations (≤100 nM) of acetylcholine induced relaxation in arteries from both groups, however highconcentrations (≥ 1 μM) of acetylcholine induced contraction in arteries from SHR, but not in WKY[Relaxation to acetylcholine [Area Under the curve (AUC)]: WKY: 396.6 ± 17.7 vs. SHR-control:296.0 ± 26.7*, t-test *vs. WKY, p=0.03). Treatment with the mediators did not change relaxationin arteries from WKY (AUC: Vehicle: 396.6 ±17.7 vs. RvD1: 402.8 ± 18.0; LXA4: 399.0 ± 18.4,p>0.05). However, incubation with RvD1 or LXA4 reduced acetylcholine induced-contraction inarteries from SHR (AUC: Vehicle: 296.0 ± 26.7 vs. RvD1: 372.5 ± 18.5*; LXA4: 376.8 ± 23.6*, t-test *vs. vehicle, p<0.05). Lipidomic analysis showed that precursors for pro-resolving lipidmediators are decreased in SHR [DHA (pmol/mL): WKY: 5637.5 ± 275.3 vs. SHR: 4509.2 ±453.9*, AA: WKY:16018.3 ± 351.3 vs. SHR: 13928.5 ± 959.5 *vs. WKY, p<0.05]. Overall, theseresults suggest that resolution of inflammation and the pro-resolving lipid mediators, RvD1 orLXA4, may be used as a new therapeutic tool to improve vascular function in hypertension.

Abstract P058: Female Rats Artificially Selected For Low Vs. High Intrinsic Aerobic Capacity Display Divergent Mechanisms In Vascular Inflammation

Hypertension is an important clinical symptom of metabolic syndrome (MetS). Rats selectively bred for low intrinsic aerobic capacity (LCR) are animal models for MetS, and present with increased blood pressure and vascular dysfunction. In contrast, rats selected for high intrinsic aerobic capacity (HCR) display reduced vascular inflammation and no metabolic abnormalities. Two important enzymes for vascular inflammation and the resolution of inflammation are cyclooxygenase (COX) and lipoxygenase (LOX), respectively; however, it is unknown whether COX and LOX play a role in the vascular function of LCR and HCR. We hypothesized that mesenteric resistance arteries (MRA) from untrained LCR present increased COX activity, while arteries from HCR show decreased COX and increased LOX activity.

Female (18-38 weeks old) LCR, HCR, and high response trained (HRT) rats, control, were used. HRT rats present higher intrinsic aerobic capacity than LCR, but lower than HCR. MRA were mounted onto a wire myograph. One-way ANOVA: p<0.05: *vs. control (HRT); # vs. HCR; & vs. absence of indomethacin (INDO), a COX inhibitor. LCR rats showed increased periovarian fat pad [HRT: 0.95±0.1 (n=7) vs. LCR: 1.80±0.1* # (n=7) vs. HCR: 1.18±0.1 (n=7) (g)]. No significant differences were observed in the KCl (120 mM), acetylcholine, and sodium-nitroprusside-induced responses. However, LCR presented a decrease in phenylephrine (PE)-induced contraction [PE: E max %: HRT: 103±3 (n=8); LCR: 74±9* # (n=11); HCR: 112±5 (n=9)]. Inhibiting COX [INDO, 10 μM] decreased contraction in HRT arteries, but had little effect on HCR arteries. Contrarily, INDO abolished contraction in MRA from LCR [PE+INDO: E max %: HRT: 31±18 & (n=7); LCR: 2±0.9 & (n=8); HCR: 77±9 (n=8)]. Lipoxin (LXA4), a LOX-derived mediator for resolution of inflammation, induced contraction in MRA from HCR, but relaxation in LCR and HRT arteries [LXA4: E max %: HRT: -69±19 (n=4); LCR: -18±9 (n=3); HCR: 11±5 (n=4)*]. Thus, HCR are unresponsive to COX inhibition, suggesting a change from a normal inflammatory state to a higher resolution state. LCR display low-grade chronic inflammation via increased COX activity. These data reveal novel, inherited mechanisms for vascular physiology in high vs. low intrinsic aerobic capacity.

The CXCR4-LASP1-eIF4F Axis Promotes Translation of Oncogenic Proteins in Triple-Negative Breast Cancer Cells

Triple-negative breast cancer (TNBC) remains clinically challenging as effective targeted therapies are lacking. In addition, patient mortality mainly results from the metastasized lesions. CXCR4 has been identified to be one of the major chemokine receptors involved in breast cancer metastasis. Previously, our lab had identified LIM and SH3 Protein 1 (LASP1) to be a key mediator in CXCR4-driven invasion. To further investigate the role of LASP1 in this process, a proteomic screen was employed and identified a novel protein-protein interaction between LASP1 and components of eukaryotic initiation 4F complex (eIF4F). We hypothesized that activation of the CXCR4-LASP1-eIF4F axis may contribute to the preferential translation of oncogenic mRNAs leading to breast cancer progression and metastasis. To test this hypothesis, we first confirmed that the gene expression of CXCR4, LASP1, and eIF4A are upregulated in invasive breast cancer. Moreover, we demonstrate that LASP1 associated with eIF4A in a CXCL12-dependent manner via a proximity ligation assay. We then confirmed this finding, and the association of LASP1 with eIF4B via co-immunoprecipitation assays. Furthermore, we show that LASP1 can interact with eIF4A and eIF4B through a GST-pulldown approach. Activation of CXCR4 signaling increased the translation of oncoproteins downstream of eIF4A. Interestingly, genetic silencing of LASP1 interrupted the ability of eIF4A to translate oncogenic mRNAs into oncoproteins. This impaired ability of eIF4A was confirmed by a previously established 5′UTR luciferase reporter assay. Finally, lack of LASP1 sensitizes 231S cells to pharmacological inhibition of eIF4A by Rocaglamide A as evident through BIRC5 expression. Overall, our work identified the CXCR4-LASP1 axis to be a novel mediator in oncogenic protein translation. Thus, our axis of study represents a potential target for future TNBC therapies.

A pilot program of contraceptive continuation in six school-based clinics

PURPOSE

Few school-based health centers (SBHC) in the United States dispense contraceptives on-site and little is known about contraceptive continuation in these health centers.

METHODS

An 11-month contraceptive continuation pilot project offering monthly reproductive health assessment and counseling to students enrolled in Baltimore school clinics was evaluated. One hundred-forty-three women voluntarily enrolled in the study over a seven month period. A monthly contraceptive calendar was developed to collect data on contraceptive use, pregnancy and STD risk, sexual behavior and parental support for contraceptive use. Physical assessment was provided as needed to assess the presence of STD's or pregnancy. Data were analyzed for the month prior to enrollment in the program and eleven months after entry into the program.

RESULTS

Both contraceptive (OCP) use and abstinence increased over the course of the program. Condom use remained at approximately 30% with frequent use of OCP's and condoms, condoms or abstinence. Program drop-out was common. Thirteen students became pregnant while enrolled in the program and 35% of the students were diagnosed with one or more sexually transmitted diseases. Partner-switching was common, although two or more partners within any one month was rare.

CONCLUSIONS

Monthly follow-up provided through SBHCs can improve contraceptive use although dropout rate and contraceptive failure remain high.