Kim M. Holwerda

Hydrogen Sulfide Attenuates sFlt1-Induced Hypertension and Renal Damage by Upregulating Vascular Endothelial Growth Factor

Soluble fms-like tyrosine kinase 1 (sFlt1), a circulating antiangiogenic protein, is elevated in kidney diseases and contributes to the development of preeclampsia. Hydrogen sulfide is a vasorelaxant and proangiogenic gas with therapeutic potential in several diseases. Therefore, we evaluated the potential therapeutic effect and mechanisms of action of hydrogen sulfide in an animal model of sFlt1-induced hypertension, proteinuria, and glomerular endotheliosis created by adenovirus-mediated overexpression of sFlt1 in Sprague-Dawley rats. We injected sFlt1-overexpressing animals intraperitoneally with the hydrogen sulfide-donor sodium hydrosulfide (NaHS) (50 µmol/kg, twice daily) or vehicle (n=7 per group). Treatment with NaHS for 8 days significantly reduced sFlt1-induced hypertension, proteinuria, and glomerular endotheliosis. Measurement of plasma protein concentrations with ELISA revealed a reduction of free plasma sFlt1 and an increase of free plasma vascular endothelial growth factor (VEGF) after treatment with NaHS. Renal VEGF-A mRNA expression increased significantly with NaHS treatment. In vitro, NaHS was proangiogenic in an endothelial tube assay and attenuated the antiangiogenic effects of sFlt1. Stimulation of podocytes with NaHS resulted in both short-term VEGF release (120 minutes) and upregulation of VEGF-A mRNA levels (24 hours). Furthermore, pretreatment of mesenteric vessels with a VEGF receptor 2-neutralizing antibody significantly attenuated NaHS-induced vasodilation. These results suggest that hydrogen sulfide ameliorates sFlt1-induced hypertension, proteinuria, and glomerular endotheliosis in rats by increasing VEGF expression. Further studies are warranted to evaluate the role of hydrogen sulfide as a novel therapeutic agent for vascular disorders such as preeclampsia.

Hydrogen sulfide producing enzymes in pregnancy and preeclampsia

Preeclampsia, a human pregnancy specific disorder is characterized by an anti-angiogenic state. As hydrogen sulfide (H(2)S) has pro-angiogenic and anti-oxidative characteristics, we hypothesized that H(2)S levels could play a role in the pathogenesis of preeclampsia and studied the placental expression of the H(2)S-producing enzymes cystathionine-γ-lyase (CSE) and cystathionine-β-synthase (CBS). CBS and CSE protein are expressed in the fetal-placental endothelium and CBS only in Hofbauer cells. CBS mRNA expression is decreased (p = 0.002) in early-onset preeclampsia, while CSE mRNA is unchanged. Thus, down regulation of CBS during early-onset preeclampsia may result in less H(2)S-production and may aid in the anti-angiogenic state.

Hydrogen sulfide : role in vascular physiology and pathology

Purpose of reviewHydrogen sulfide (H2S), a colorless gas that is endogenously generated in mammals from cysteine, has important biological functions. Within the vasculature it regulates vessel tone and outgrowth of new vessels. This review summarizes recent literature on H2S signaling in the vasculature and its therapeutic potential in vascular disorders Recent findingsH2S is able to induce vasorelaxation via ATP-sensitive potassium channels in vascular smooth muscle cells. Large-conductance calcium-dependent K+-channels and Kv7 voltage-gated K+-channels are also involved in H2S signaling. Vascular endothelial growth factor is the key downstream mediator that is involved in H2S induced angiogenesis. By having both direct effects on its receptor and increasing the bioavailability of vascular endothelial growth factor, H2S is proangiogenic. H2S-based therapies in vascular diseases are an expanding area of research. The applications of several compounds, such as natural donors and synthetic slow release compounds, have been extensively studied in vascular diseases such as hypertension, ischemia–reperfusion disorders and preeclampsia. SummaryH2S has a key role in vascular homeostasis during physiology and in pathological states. H2S-based therapies may have a role in several vascular diseases.

Circulating Lymphangiogenic Factors in Preeclampsia

Background. Preeclampsia (PE), a human pregnancy-specific disorder is characterized by an anti-angiogenic state due to high levels of circulating soluble vascular endothelial growth factor 1 (sVEGFR-1). However, the role of lymphangiogenesis in PE has not been investigated. Recently, impaired vascular endothelial growth factor C (VEGF-C) (factor that regulates lymphangiogenesis) signaling has been implicated in the pathogenesis of interstitial edema and salt-sensitive hypertension. Therefore, we hypothesized that circulating VEGF-C and its circulating receptors (sVEGFR-2 and sVEGFR-3) may also be altered in PE and correlate with the severity of the phenotype. Methods. We analyzed plasma levels of VEGF-C, sVEGFR-1, sVEGFR-2, and sVEGFR-3 in women with gestational hypertension (GHTN, n = 20), PE (n = 20), and normotensive pregnancies (NP, n = 20) in the third trimester and values were reported as mean ± SD in pg/mL. Results. As previously reported, sVEGFR-1 levels were significantly higher in subjects with PE (19,938 ± 12,973) than in GHTN (7156 ± 5432), p < 0.01 or NP (7760 ± 6018), p < 0.01. VEGF-C levels were lower in subjects with GHTN (676 ± 323) than in PE (1335 ± 625), p < 0.01, but not statistically different than in NP (971 ± 556), p = 0.11. There was a trend toward lower sVEGFR-2 in PE as compared to GHTN or NP. Interestingly, sVEGFR-3 was significantly lower in PE (54,371 ± 21,107) as compared to NP (83,709 ± 24,983), p < 0.01, but not different as compared to GHTN (54,642 ± 26,947). The ratio of sVEGFR-2 + sVEGFR-3/VEGF-C was dramatically lower during PE (57 ± 38) as compared to GHTN (113 ± 72), p < 0.01 or NP (133 ± 91), p < 0.01. Conclusions. PE is characterized by circulating pro-lymphangiogenic state as evidenced by decreased sVEGFR-3, slightly decreased sVEGFR-2, increased VEGF-C, and a dramatically lower ratio of sVEGFR-2 + sVEGFR-3/VEGF-C. Our data suggest that the circulating pro-lymphangiogenic state during PE may be a compensatory response to edema and hypertension. Additional studies are needed to evaluate the clinical relevance of the altered lymphangiogenic signaling pathway during PE.

Gasotransmitters: A Solution for the Therapeutic Dilemma in Preeclampsia?

Preeclampsia complicates 2% to 8% of all pregnancies and is a major contributor to maternal mortality worldwide. The only therapy is delivery, often before term.1 Nitric oxide, carbon monoxide, and hydrogen sulfide are gasotransmitters that regulate vascular development, vascular tone, and affect antioxidant status.2 Abnormalities in gasotransmitter signaling and production are linked to hypertension, atherosclerosis, and inflammation.2 Drugs that enhance gasotransmitter signaling have proven therapeutic potential in the clinical and experimental setting. Gasotransmitters are involved in the vascular adaptations of normal pregnancy,3–7 and experimental studies have shown that abnormal production is associated with preeclampsia.8–12 The aim of this review is to give an overview of the role of gasotransmitters in the physiology of pregnancy and relate their aberrant production to preeclampsia. Specific emphasis will be put on and overview their therapeutic potential for preeclampsia. Preeclampsia is defined by hypertension and proteinuria during the second half of gestation. Although the exact cause of preeclampsia is unknown, the placenta and the maternal inflammatory response play a key role in its pathogenesis.1,13 Preeclampsia is often described as a 2-stage disease. During placentation in normal pregnancy, trophoblasts invade into the endometrium and spiral arteries resulting in spiral artery dilation.1 In preeclampsia, trophoblast invasion is incomplete resulting in inadequate spiral artery remodeling and placental hypoperfusion; this is stage 1 of the disease.1 Subsequently, the oxygen-deprived placenta produces factors that enter the maternal circulation, causing maternal endothelial dysfunction and maternal immune response activation, leading to the signs of preeclampsia; this is stage 2 of the disease.1 Some of the factors produced by the placenta are antiangiogenic factors, such as soluble fms-like tyrosine kinase receptor 1 (sFlt1).14 They are (partly) responsible for the maternal syndrome in preeclampsia because increased sFlt1 is …

The association of single nucleotide polymorphisms of the maternal cystathionine-β-synthase gene with early-onset preeclampsia

OBJECTIVES Preeclampsia (PE) is a pregnancy complication, characterized by hypertension and proteinuria. The transsulfuration pathway may be involved in its pathophysiology, since homocysteine, cystathionine and cysteine are increased in PE. Cystathionine-β-synthase (CBS) is a key-enzyme in the pathway, converting homocysteine into cysteine via cystathionine. Another product of CBS is hydrogen sulfide (H2S), a vasodilatory, proangiogenic and cytoprotective gas that is thought to play a role in placental and vascular function during pregnancy. Since single nucleotide polymorphisms (SNPs) can affect CBS expression and/or function, we studied tag-SNPs in the CBS gene in PE patients. STUDY DESIGN Controls (n=75), early-onset (n=45), and late-onset PE (n=52) cases were genotyped for six tag-SNPs in the CBS gene; rs12329764, rs2851391, rs234713, rs234706, rs1789953, and rs11203172. Plasma homocysteine, cysteine and cystathionine were determined during pregnancy. MAIN OUTCOME MEASURES Early-onset PE, late-onset PE. RESULTS Women with the minor allele of rs11203172 have a reduced risk for early-onset PE. Compared to women without the minor allele, normotensive pregnant women with the minor allele of rs11203172 and rs234713 have lower cysteine levels. Women with the minor allele of rs1789953 have increased levels of cysteine and cystathionine, compared to women without. CONCLUSION The CBS tag-SNP rs11203172 is associated with a decreased risk for early-onset PE. Decreased cysteine concentrations in normotensive pregnant women carrying the minor allele of rs11203172, may be due to increased cysteine conversion to H2S by CBS. Higher H2S levels may positively affect placentation and vascular function during pregnancy and decrease their risk for PE.

PP013. Single nucleotide polymorphisms of the maternal cystathionine-b-synthase gene are associated with preeclampsia (PE)

INTRODUCTION Cystathionine-b-synthase (CBS) produces the vasodilatory and anti-inflammatory hydrogen sulfide (H2S) by conversion of homocysteine (Hcy). H2S is involved in placental vascular tone regulation. Previously, we showed that woman with PE have hyperhomocysteinemia and decreased placental CBS gene expression. OBJECTIVES Aberrant CBS gene expression may play a role in hyperhomocysteinemia and decreased H2S and could be involved in pathogenesis of PE. We studied whether the presence of CBS single nucleotide polymorphisms (SNPs) is associated with the development of PE. METHODS Six CBS SNPs (rs12329764, rs2851391, rs234713, rs234706, rs1789953, rs11203172) were genotyped in 99 controls, 60 severe, and 39 mild PE cases. Severe and mild PE cases were additionally subdivided into late- (>34 weeks) and early-onset (<34 weeks) PE. The association of the alleles with development PE was tested with logistic regression. RESULTS Two of the six SNPs are associated with PE. The minor allele for rs11203172 reduces the risk for developing severe PE (OR[95% CI]=0.54[0.21-0.94], p=0.023). The minor allele for rs234706, which is associated with low Hcy, increased the risk to develop mild, late-onset PE (2.10[1.15-3.85], p=0.016). CONCLUSION SNPs in the CBS gene are associated with risk of developing PE. Within the CBS gene, SNPs associated with both a decreased and an increased risk to develop PE were found. Altered effectiveness of CBS may affect PE through decreased H2S production or Hcy accumulation.

PP016. Circulating lymphangiogenic factors in preeclampsia.

INTRODUCTION Preeclampsia, a human pregnancy specific disorder is characterized by an anti-angiogenic state due to high levels of circulating soluble vascular endothelial growth factor 1 (sVEGFR1). However, the role of lymphangiogenesis in preeclampsia has not been investigated. Recently, impaired VEGF-C (factor that regulates lymphangiogenesis) signalling has been implicated in the pathogenesis of interstitial edema and salt-sensitive hypertension. OBJECTIVES Therefore, we hypothesized that circulating VEGF-C and its circulating receptors (sVEGFR2 and sVEGFR3) may also be altered in preeclampsia and correlate with the severity of the phenotype. METHODS We analyzed plasma levels of VEGF-C, sVEGFR1, sVEGFR2 and sVEGFR3 in women with gestational hypertension (GHTN, n=20), preeclampsia (PE, n=20) and normotensive pregnancies (NP, n=20) in the third trimester and values reported as mean±SD in pg/ml. RESULTS As previously reported, sVEGFR1 levels were significantly higher in subjects with PE (19938 ± 12973) than in GHTN (7156±5432), p<0.01 or NP (7760±6018), p<0.01. VEGF-C levels were lower in subjects with GHTN (676±323) than in PE (1335±625), p<0.01, but not statistically different than in NP (971±556), p=0.11. There was a trend towards lower sVEGFR-2 in PE as compared to GHTN or NP. Interestingly sVEGFR-3 was significantly lower in PE (54,371±21,107) as compared to NP (83,709±24,983), p<0.01, but not different as compared to GHTN (54,642±26,947). The ratio of sVEGFR-2+sVEGFR-3/VEGF-C was dramatically lower during PE (57±38) as compared to GHTN (113±72), p<0.01 or NP (133±91), p<0.01. CONCLUSION Preeclampsia is characterized by circulating pro-lymphangiogenic state as evidenced by decreased sVEGFR-3, slightly decreased VEGFR-2, increased VEGF-C and a dramatically lower ratio of sVEGFR2+sVEGFR3/VEGF-C. Our data suggests that the circulating pro-lymphoangiogenic state during preeclampsia may be a compensatory response to edema and hypertension. Additional studies are needed to evaluate the clinical relevance of the altered lymphangiogenic signalling pathway during preeclampsia.