Sex Differences in Renal Sphingosine‐1‐Phosphate Signaling Pathway and Blood Pressure of Intrauterine Growth Restricted Mice

Intrauterine growth restriction (IUGR) is a risk factor for hypertension, cardiovascular (CV), and kidney diseases in later life. However, the underlying mechanisms remain unclear. We previously reported IUGR in mice programs hypertension in male and female offspring before puberty (at 5 weeks of age). Sphingosine‐1‐phosphate (S1P) is a signaling sphingolipid important for fetal CV development in utero and regulation of CV function after birth. S1P receptors (S1PR1,2,3) and sphingosine kinases (SPHK1,2) are widely expressed in the CV system. S1P signaling has been reported to have a protective role against kidney injury and S1P3 is involved in controlling BP. We previously showed that S1P plays a role in hypertension of adult male IUGR mice and whole kidney S1PR3 expression is altered in male IUGR during‐ and post‐nephrogenesis. Although the potential role of the S1P signaling pathway on BP of male IUGR is reported, whether different sexes exhibit variations in these parameters is still unclear. This study aimed to determine if IUGR in mice induced by placental insufficiency programs sex differences in BP and renal S1P signaling protein expression. C57BL/6J mice underwent sham or reduced uterine perfusion (RUP) surgery at day 13 of gestation with delivery at full term. IUGR offspring (from RUP dams) had lower birth weight than controls ( P <0.05). At 24 weeks of age, we assessed BP via carotid catheter in the conscious state. Male IUGR offspring had a significantly higher BP compared to male controls (control: 112.1±2.1, IUGR: 125.0±3.7 mmHg; N=7, P <0.05). Female IUGRs had a similar BP compared to female controls (control: 113.8±3.8, IUGR: 117.8±2.8 mmHg; N=5, ns). This data suggests sex differences in IUGR programming hypertension. Moreover, male IUGR BP was significantly decreased ( P <0.05) after systemical acute administration of a non‐specific S1PR agonist (1 mg/kg BW I.P., FTY720) similarly to what we had previously reported. Then, we assessed the expression pattern of S1P signaling protein in kidney using immunohistochemistry (IHC) with N=3–4 animals for each group. Digital images were prepared for analyses using ImageJ. Antigen‐positive area was automatically separated using a color deconvolution plugin. Mean gray value was then measured and optical density was calculated and reported as fold changes. Males and females of both control and IUGR groups exhibited similar patterns of S1PR1 expression with 2‐fold higher in medulla compared to cortex ( P 0.001). Sex differences in S1PR2 expression was found in male controls and male IUGRs (2‐fold higher than female, P <0.05) within the cortex. Male and female controls had similar patterns of S1PR3 expression in both cortex and medulla. Yet, sex differences were found ( P <0.001) in IUGRs with S1PR3 levels markedly lower in males. No differences were observed in SPHK1. No sex differences were found in neither controls nor IUGRs for SPHK2 despite female IUGRs having higher levels than female controls in the medulla ( P <0.05). Together our data suggest that IUGR programs sex differences in BP and renal S1P signaling protein expression thereby contributing to an increase in sensitivity to an S1PRs agonist. Thus, S1P signaling is a potential mechanism underlying the sex differences in BP of IUGRs. Support or Funding Information Dr. Intapad was supported by funding from the AHA 16SDG27770041, ASN Kidney Research Career Development grant, and NIH P20GM104357.