Sebastiaan Wesseling

The Vascular Endothelial Growth Factor Receptor Inhibitor Sunitinib Causes a Preeclampsia-Like Syndrome With Activation of the Endothelin System

Angiogenesis inhibition is an established treatment for several tumor types. Unfortunately, this therapy is associated with adverse effects, including hypertension and renal toxicity, referred to as “preeclampsia.” Recently, we demonstrated in patients and in rats that the multitarget tyrosine kinase inhibitor sunitinib induces a rise in blood pressure (BP), renal dysfunction, and proteinuria associated with activation of the endothelin system. In the current study we investigated the effects of sunitinib on rat renal histology, including the resemblance with preeclampsia, as well as the roles of endothelin 1, decreased nitric oxide (NO) bioavailability, and increased oxidative stress in the development of sunitinib-induced hypertension and renal toxicity. In rats on sunitinib, light and electron microscopic examination revealed marked glomerular endotheliosis, a characteristic histological feature of preeclampsia, which was partly reversible after sunitinib discontinuation. The histological abnormalities were accompanied by an increase in urinary excretion of endothelin 1 and diminished NO metabolite excretion. In rats on sunitinib alone, BP increased (&Dgr;BP: 31.6±0.9 mm Hg). This rise could largely be prevented with the endothelin receptor antagonist macitentan (&Dgr;BP: 12.3±1.5 mm Hg) and only mildly with Tempol, a superoxide dismutase mimetic (&Dgr;BP: 25.9±2.3 mm Hg). Both compounds could not prevent the sunitinib-induced rise in serum creatinine or renal histological abnormalities and had no effect on urine nitrates but decreased proteinuria and urinary endothelin 1 excretion. Our findings indicate that both the endothelin system and oxidative stress play important roles in the development of sunitinib-induced proteinuria and that the endothelin system rather than oxidative stress is important for the development of sunitinib-induced hypertension.

Maternal Supplementation With Citrulline Increases Renal Nitric Oxide in Young Spontaneously Hypertensive Rats and Has Long-Term Antihypertensive Effects

NO deficiency is associated with development of hypertension. Defects in the renal citrulline-arginine pathway or arginine reabsorption potentially reduce renal NO in prehypertensive spontaneously hypertensive rats (SHRs). Hence, we investigated genes related to the citrulline-arginine pathway or arginine reabsorption, amino acid pools, and renal NO in 2-week-old prehypertensive SHRs. In addition, because perinatally supporting NO availability reduces blood pressure in SHRs, we supplemented SHR dams during pregnancy and lactation with citrulline, the rate-limiting amino acid for arginine synthesis. In female offspring, gene expression of argininosuccinate synthase (involved in renal arginine synthesis) and renal cationic amino acid Y-transporter (involved in arginine reabsorption) were both decreased in 2-day and 2-week SHRs compared with normotensive WKY, although no abnormalities in amino acid pools were observed. In addition, 2-week-old female SHRs had much less NO in their kidneys (0.46±0.01 versus 0.68±0.05 nmol/g of kidney weight, respectively; P<0.001) but not in their heart. Furthermore, perinatal supplementation with citrulline increased renal NO to 0.59±0.02 nmol/g of kidney weight (P<0.001) at 2 weeks and persistently ameliorated the development of hypertension in females and until 20 weeks in male SHR offspring. Defects in both the renal citrulline-arginine pathway and in arginine reabsorption precede hypertension in SHRs. We propose that the reduced cationic amino acid transporter disables the developing SHR kidney to use arginine reabsorption to compensate for reduced arginine synthesis, resulting in organ-specific NO deficiency. This early renal deficiency and its adverse sequels can be corrected by perinatal citrulline supplementation persistently in female and transiently in male SHRs.

IFNγ-dependent SOCS3 expression inhibits IL-6-induced STAT3 phosphorylation and differentially affects IL-6 mediated transcriptional responses in endothelial cells

IL-6 has pro- and anti-inflammatory effects and is involved in endothelial cell (EC) dysfunction. The anti-inflammatory effects of IL-6 are mediated by signal transducer and activator of transcription-3 (STAT3), which is importantly controlled by suppressor of cytokine signaling 3 (SOCS3). Therefore, cytokines that modulate SOCS3 expression might inhibit the anti-inflammatory effects of IL-6. We hypothesized that in EC, interferon-gamma (IFNgamma)-induced SOCS3 expression leads to inhibition of IL-6-induced STAT3 activation and IL-6-dependent expression of anti-, but not pro-inflammatory, target genes. IFNgamma activated STAT1 and STAT3 and increased SOCS3 expression in EC. IL-6 only activated STAT3 and induced SOCS3 expression. IFNgamma pretreatment of EC inhibited IL-6-induced STAT3 activation accompanied by increased SOCS3 protein. Inhibition of SOCS3 expression, using costimulation, Act-D, and small interfering RNA (siRNA), subsequently implicated the importance of IFNgamma-induced SOCS3 in this phenomenon. Pretreatment of EC with IFNgamma also affected the transcriptional program induced by IL-6. We identified 1) IL-6 anti-inflammatory target genes that were inhibited by IFNgamma, 2) IFNgamma-target genes of pro-inflammatory nature that were increased in response to IL-6 in the presence of IFNgamma, and 3) a set of target genes that were increased upon IL-6 or IFNgamma alone, or combined IFNgamma and IL-6. In summary, by increasing SOCS3 expression in EC, IFNgamma can selectively inhibit STAT3-dependent IL-6 signaling. This in turn leads to decreased expression of some EC protective genes. In contrast, other genes of pro-inflammatory nature are not inhibited or even increased. This IFNgamma-induced shift in IL-6 signaling to a pro-inflammatory phenotype could represent a novel mechanism involved in EC dysfunction.

Soluble epoxide hydrolase in the generation and maintenance of high blood pressure in spontaneously hypertensive rats

We hypothesized that perinatal inhibition of soluble epoxide hydrolase (SEH), which metabolizes epoxyeicosatrienoic acids in the arachidonic acid (AA) cascade, with an orally active SEH inhibitor, 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA), would persistently reduce blood pressure (BP) in adult SHR despite discontinuation of AUDA at 4 wk of age. Renal cytoplasmic epoxide hydrolase-2 (Ephx2) gene expression was enhanced in SHR vs. WKY from 2 days to 24 wk. Effects of perinatal treatment with AUDA, supplied to SHR dams until 4 wk after birth, on BP in female and male offspring and renal oxylipin metabolome in female offspring were observed and contrasted to female SHR for direct effects of AUDA (8-12 wk). Briefly, inhibition of SEH was effective in persistently reducing BP in female SHR when applied during the perinatal phase. This was accompanied by marked increases in major renal AA epoxides and decreases in renal lipoxygenase products of AA. Early inhibition of SEH induced a delayed increase in renal 5-HETE at 24 wk, in contrast to a decrease at 2 wk. Inhibition of SEH in female SHR from 8 to 12 wk did not reduce BP but caused profound decreases in renal 15(S)-HETrE, LTB4, TBX2, 5-HETE, and 20-HETE and increases in TriHOMEs. In male SHR, BP reduction after perinatal AUDA was transient. Thus, Ephx2 transcription and SEH activity in early life may initiate mechanisms that eventually contribute to high BP in adult female SHR. However, programmed BP-lowering effects of perinatal SEH inhibition in female SHR cannot be simply explained by persistent reduction in renal SEH activity but rather by more complex and temporally dynamic interactions between the renal SEH, lipoxygenase, and cyclooxygenase pathways.

Beneficial effects of diminished production of hydrogen sulfide or carbon monoxide on hypertension and renal injury induced by NO withdrawal

Whether NO, carbon monoxide (CO) and hydrogen sulfide (H2S) compensate for each other when one or more is depleted is unclear. Inhibiting NOS causes hypertension and kidney injury. Both global depletion of H2S by cystathionine γ‐lyase (CSE) gene deletion and low levels of exogenous H2S cause hypertension. Inhibiting CO‐producing enzyme haeme oxygenase‐1 (HO‐1) makes rodents hypersensitive to hypertensive stimuli. We hypothesized that combined inhibition of NOS and HO‐1 exacerbates hypertension and renal injury, but how combined inhibition of NOS and CSE affect hypertension and renal injury was unclear.

Salt sensitivity of blood pressure: developmental and sex-related effects

Epidemiologic studies have shown convincingly that drastically reducing salt intake in the community is accompanied by blood pressure reductions that are comparable to those achieved by antihypertensive medication. Moreover, many subjects with hypertension are salt sensitive. This implies that, in these subjects, blood pressure is more responsive to changes in salt intake than in subjects with normal blood pressure. The presence of conventional risk factors associated with the metabolic syndrome correlates with salt sensitivity. However, women appear to be more salt sensitive than men. Sparse data indicate that the salt sensitivity of blood pressure is greater in subjects with low birth weight. Experimental studies in rats have also shown that hypertensive offspring of dams maintained on low-protein diets throughout or in late pregnancy are more salt sensitive. This is accompanied by increased expression of the thick ascending limb Na-K-2Cl symporter (NKCC2). Perinatal interventions aimed at persistently lowering blood pressure in genetically hypertensive rats have consistently proven to be very effective and are often accompanied by a wave of natriuresis exclusively at 4 wk of age. In sum, in addition to conventional metabolic risk factors for cardiovascular disease, low birth weight and possibly its sequels such as catch-up growth should be viewed as modifiable risk factors for salt sensitivity of blood pressure. Female sex may also be a nonmodifiable risk factor for salt sensitivity. Experimental data indicate that NKCC2 may well be an important determinant of salt sensitivity in acquired (developmental) hypertension.

dl-propargylglycine reduces blood pressure and renal injury but increases kidney weight in angiotensin-II infused rats

Hydrogen sulfide (H2S), carbon monoxide (CO) and nitric oxide (NO) share signaling and vasorelaxant properties and are involved in proliferation and apoptosis. Inhibiting NO production or availability induces hypertension and proteinuria, which is prevented by concomitant blockade of the H2S producing enzyme cystathionine γ-lyase (CSE) by d,l-propargylglycine (PAG). We hypothesized that blocking H2S production ameliorates Angiotensin II (AngII)-induced hypertension and renal injury in a rodent model. Effects of concomitant administration of PAG or saline were therefore studied in healthy (CON) and AngII hypertensive rats. In CON rats, PAG did not affect systolic blood pressure (SBP), but slightly increased proteinuria. In AngII rats PAG reduced SBP, proteinuria and plasma creatinine (180 ± 12 vs. 211 ± 19 mmHg; 66 ± 35 vs. 346 ± 92 mg/24 h; 24 ± 6 vs. 47 ± 15 μmol/L, respectively; p < 0.01). Unexpectedly, kidney to body weight ratio was increased in all groups by PAG (p < 0.05). Renal injury induced by AngII was reduced by PAG (p < 0.001). HO-1 gene expression was increased by PAG alone (p < 0.05). PAG increased inner cortical tubular cell proliferation after 1 week and decreased outer cortical tubular nucleus number/field after 4 weeks. In vitro proximal tubular cell size increased after exposure to PAG. In summary, blocking H2S production with PAG reduced SBP and renal injury in AngII infused rats. Independent of the cardiovascular and renal effects, PAG increased HO-1 gene expression and kidney weight. PAG alone increased tubular cell size and proliferation in-vivo and in-vitro. Our results are indicative of a complex interplay of gasotransmitter signaling/action of mutually compensatory nature in the kidney.

Taurine Red Bull or Red Herring

Taurine, a sulfur-containing amino acid (Figure), has been termed a functional nutrient that could be used to protect against, among others, diabetes mellitus and atherosclerosis.1 Indeed, an increasing body of literature supports the use of taurine supplements. Because taurine has very diverse functions, notably, intracellular osmoregulation and bile acid formation, and is abundantly present in several organs, multiple pathways could be involved. Some of these are discussed in this editorial. Figure. A simplified biosynthesis pathway from methionine to taurine. Methionine is converted to homocysteine in 3 steps. Homocysteine is used as a substrate to form cysteine in 2 steps but can also be converted back to methionine by 2 different mechanisms. Cysteine, precursor for the important antioxidant glutathione and the gaseous transmitter/signaling molecule H2S, can be further converted to cysteine sulfinate. Cysteine sulfinate is converted to taurine in 2 steps via 2 different pathways. Taurine can decrease methionine by decreasing uptake. Whether taurine decreases homocysteine directly or via a reduction of methionine is unclear. Of the 20 canonical amino acids, 18 are composed of carbon, hydrogen, nitrogen, and oxygen only. The remaining 2, methionine and cysteine, also contain 1 atom of sulfur. Because sulfur is not as electronegative as oxygen, the sulfur-containing amino acids play a key role in protein structure and synthesis.2 Methionine and cysteine also play important roles in cell metabolism. For instance, methionine serves as a substrate for S-adenosylmethionine, which is vital for methylation of nucleic acids, proteins, lipids, etc. In proteins, cysteine easily forms double bonds with other cysteine residues, thus determining tertiary structure and binding sites. Moreover, cysteine is substrate for glutathione, an important intracellular antioxidant, and H2S, a gas that can induce endothelial-dependent relaxation.3 Cysteine is considered a nonessential amino acid because it is synthesized …

Perinatal inhibition of NF-KappaB has long-term antihypertensive and renoprotective effects in fawn-hooded hypertensive rats

BACKGROUND Inhibition of transcription factor nuclear factor-kappa B (NFκB) is beneficial in various models of hypertension and renal disease. We hypothesized first that NFκB inhibition during renal development ameliorates hereditary hypertensive renal disease and next whether this was mediated via suppression of peroxisome proliferator-activated receptor (PPAR)γ coactivator 1α (PGC-1α). METHODS AND RESULTS Prior to the development of renal injury in fawn-hooded hypertensive (FHH) rats, a model of hypertension, glomerular hyperfiltration, and progressive renal injury, NFkB activity, measured by nuclear protein expression of NFkB subunit p65, was enhanced twofold in 2-day-old male and female FHH kidneys as compared to normotensive Wistar-Kyoto (WKY) rats (P < 0.05). Treating FHH dams with pyrrolidine di thio carbamate (PDTC), an NFκB inhibitor, from 2 weeks before birth to 4 weeks after birth diminished NFkB activity in 2-day-FHH offspring to 2-day-WKY levels (P < 0.01). Perinatal PDTC reduced systolic blood pressure from 20 weeks onwards by on average 25 mm Hg (P < 0.001) and ameliorated proteinuria (P < 0.05) and glomerulosclerosis (P < 0.05). In kidneys of 2-day-, 2-week-, and adult offspring of PDTC-treated FHH dams, PGC-1α was induced on average by 67% (quantitative polymerase chain reaction (qPCR)) suggesting that suppression of this factor by NFkB could be involved in renal damage. Follow-up experiments with perinatal pioglitazone (Pio), a PPARγ agonist, failed to confer persistent antihypertensive or renoprotective effects. CONCLUSIONS Perinatal inhibition of enhanced active renal NFκB in 2-day FHH had persistent antihypertensive and renoprotective effects. However, this was not the case for PPARγ stimulation. NFkB stimulation is therefore involved in renal damage in the FHH model of proteinuric renal disease by pathways other than via PPARγ.

Perinatal exogenous nitric oxide in fawn-hooded hypertensive rats reduces renal ribosomal biogenesis in early life

Nitric oxide (NO) is known to depress ribosome biogenesis in vitro. In this study we analyzed the influence of exogenous NO on ribosome biogenesis in vivo using a proven antihypertensive model of perinatal NO administration in genetically hypertensive rats. Fawn-hooded hypertensive rat (FHH) dams were supplied with the NO-donor molsidomine in drinking water from 2 weeks before to 4 weeks after birth, and the kidneys were subsequently collected from 2 day, 2 week, and 9 to 10-month-old adult offspring. Although the NO-donor increased maternal NO metabolite excretion, the NO status of juvenile renal (and liver) tissue was unchanged as assayed by EPR spectroscopy of NO trapped with iron-dithiocarbamate complexes. Nevertheless, microarray analysis revealed marked differential up-regulation of renal ribosomal protein genes at 2 days and down-regulation at 2 weeks and in adult males. Such differential regulation of renal ribosomal protein genes was not observed in females. These changes were confirmed in males at 2 weeks by expression analysis of renal ribosomal protein L36a and by polysome profiling, which also revealed a down-regulation of ribosomes in females at that age. However, renal polysome profiles returned to normal in adults after early exposure to molsidomine. No direct effects of molsidomine were observed on cellular proliferation in kidneys at any age, and the changes induced by molsidomine in renal polysome profiles at 2 weeks were absent in the livers of the same rats. Our results suggest that the previously found prolonged antihypertensive effects of perinatal NO administration may be due to epigenetically programmed alterations in renal ribosome biogenesis during a critical fetal period of renal development, and provide a salient example of a drug-induced reduction of ribosome biogenesis that is accompanied by a beneficial long-term health effect in both males and females.