Human soluble prorenin receptor expressed in mouse renal collecting duct shows sex-specific effect on cardiorenal function

Soluble prorenin receptor (sPRR), a component of the renin-angiotensin system (RAS), has been identified as a plasma biomarker for hypertension and cardiovascular diseases in humans. Despite studies showing that sPRR in the kidney is produced by tubular cells in the renal collecting duct (CD), its biological actions modulating cardiorenal function in physiological conditions remain unknown. Therefore, the objective of our study was to investigate whether CD-derived human sPRR (HsPRR) expression influences cardiorenal function and examine sex and circadian differences. Thus, we investigated the status of the intrarenal RAS, water and electrolyte balance, renal filtration capacity, and blood pressure (BP) regulation in CD-HsPRR and control (CTL) mice. CD-HsPRR mice were generated by breeding human sPRR-Myc-tag mice with Hoxb7/Cre mice. Renal sPRR expression increased in CD-HsPRR mice, but circulating sPRR and RAS levels were unchanged compared with CTL mice. Only female littermates expressing CD-HsPRR showed 1) increased 24-h BP, 2) an impaired BP response to an acute dose of losartan and attenuated angiotensin II (ANG II)-induced hypertension, 3) reduced angiotensin-converting enzyme activity and ANG II content in the renal cortex, and 4) decreased glomerular filtration rate, with no changes in natriuresis and kaliuresis despite upregulation of the β-subunit of the epithelial Na+ channel in the renal cortex. These cardiorenal alterations were displayed only during the active phase of the day. Taken together, these data suggest that HsPRR could interact with ANG II type 1 receptors mediating sex-specific, ANG II-independent renal dysfunction and a prohypertensive phenotype in a sex-specific manner.NEW & NOTEWORTHY We successfully generated a humanized mouse model that expresses human sPRR in the collecting duct. Collecting duct-derived human sPRR did not change circulating sPRR and RAS levels but increased daytime BP in female mice while showing an attenuated angiotensin II-dependent pressor response. These findings may aid in elucidating the mechanisms by which women show uncontrolled BP in response to antihypertensive treatments targeting the RAS, improving approaches to reduce uncontrolled BP and chronic kidney disease incidences in women.

Human Soluble Prorenin Receptor Expressed in Adipose Tissue Improves Insulin Sensitivity and Endothelial Function in Obese Female Mice

Increased circulating levels of the soluble prorenin receptor (sPRR), a component of the renin angiotensin system (RAS), plays a role in obesity, glucose, and insulin homeostasis. However, elevated plasma sPRR in diabetic patients has been shown correlated with hyperglycemia in women but not men. Hence, the current study sought to understand the contribution of human sPRR (HsPRR) produced in the adipose tissue (Adi) on adipogenesis, and glucose and insulin balance in obesity settings. Adi-HsPRR mice were generated by breeding human sPRR-Myc-tag transgenic mice with mice expressing Adiponectin/Cre. The mouse model was validated by detecting 28kDa myc-tagged HsPRR by western blotting. Adipose HsPRR expression did not change circulating sPRR in female mice fed a standard chow diet or high fat diet (HFD) but increased plasma sPRR in male Adi-HsPRR mice fed a HFD compared to HFD-fed controls. Yet, Adi-HsPRR improved insulin sensitivity, vascular relaxation and the vasodilator agent Ang 1-7 in obese female mice but not in the male counterparts. Moreover, Adi-HsPRR expression reduced the expression of the adipogenic genes SREBP1C and CD36 only in gonadal white adipose from obese female mice, signifying that adipose tissue-derived HsPRR exerts a sex-specific effect on insulin sensitivity and endothelial function which seems independent of circulating sPRR.

Abstract 066: Renal-derived Human Sprr Induces Hypernatremia And Water Retention In Male Mice But Not Female Mice

The soluble prorenin receptor (sPRR) plays an important role in fluid and electrolyte balance. In rodent models, sPRR contributes to aquaporin2(AQP2)-dependent antidiuretic action. However, there is a gap of knowledge concerning the functional role of locally produced human sPRR from the kidney. Hence, we evaluated the role of renal-derived human sPRR in fluid and electrolyte homeostasis.Human sPRR-Myc-tag transgenic mice were bred with mice expressing Hoxb7/Cre to selectively express human sPRR in the collecting duct (RHsPRR). RHsPRR and control (CTL) male and female mice were fed a standard diet for 10 months (n=8-11/group). Body weight was examined weekly, body composition monthly and water balance at study endpoint. Western blot analysis depicted the presence of human sPRR-Myc-tag (28 KDa) in the cortex and medulla of RHsPRR male and female mice validating the humanized mouse model.Renal-derived human sPRR did not change body weight in male or female mice (Male: CTL: 34±1, RHsPRR: 33±1 g; Female: CTL: 28±1, RHsPRR: 30±1 g) nor kidney function assessed by GFR (Male: CTL: 817±83, RHsPRR: 1088±163 μl/min/100gBW; Female: CTL: 1057±75, RHsPRR: 875±89 μl/min/100gBW). In male mice, renal-derived human sPRR significantly elevated plasma sodium (Male: CTL: 115±4, RHsPRR: 127±3 mmol/L; P<0.05) and ENaC gene expression (M: 1.7±0.7 and 3.7±0.9 2 -ΔΔCT , P<0.05). Urine flow rate was decreased (Male: CTL: 1.0±0.2, RHsPRR: 0.6±0.2 ml; P<0.05) and AQP2 protein expression was increased in male RHsPRR mice compared to CTL (M: 0.13±0.05 and 0.44±0.12 AU, P<0.05), suggesting that renal-derived human sPRR elicits hypernatremia by stimulating sodium reabsorption via ENaC-dependent mechanism and water reabsorption by AQP2 expression.In female mice, renal-derived human sPRR did not change plasma sodium (Female: CTL: 120±7, RHsPRR: 118±5 mmol/L), ENaC gene expression (F: 1.2±0.2 and 1.4±0.1 2 -ΔΔCT ), urine flow rate (Female: CTL: 0.4±0.1, RHsPRR: 0.5±0.1 ml) or AQP2 protein expression (F: 0.20±0.03 and 0.20±0.06 AU, P<0.05).Our data suggest that renal cortical and medullary human sPRR regulates water and electrolyte balance in a sex specific-manner. Translationally, human sPRR could be a promising therapeutic target to treat hypernatremia in men.

Abstract 041: Renal-derived Human Sprr Increases Blood Pressure In Female Mice But Not In Male Mice

The soluble prorenin receptor (sPRR) plays an important role in blood pressure regulation. In rodent models, sPRR contributes to Ang II production by increasing renin activity and systolic blood pressure (SBP). However, there is a gap of knowledge concerning the functional role of locally produced human sPRR from the kidney in blood pressure regulation. Therefore, we evaluated the role of renal-derived human sPRR in SBP control.Human sPRR-Myc-tag transgenic mice were bred with mice expressing Hoxb7/Cre to selectively express human sPRR in the collecting duct (RHsPRR). RHsPRR and control (CTL) male and female mice were fed a standard diet for 10 months (n=8-11/group). Body weight was examined weekly and SBP measured by radio-telemetry. Western blot analysis depicted the presence of human sPRR-Myc-tag (28 KDa) in the cortex and medulla of RHsPRR male mice which validated the humanized mouse model. Renal-derived human sPRR did not change body weight in male or female mice (M: CTL: 34±1, RHsPRR: 33±1 g; F: CTL: 28±1, RHsPRR: 30±1 g). Circulating sPRR was also unchanged in male and female mice (M: 3995±643 and 4342±500pg/ml, F: 3479±194 and 3948±238pg/ml). SBP increased significantly in female RHsPRR mice compared to CTL (F: 118.7±2 and 127.2±3 mmHg, P<0.05) but not in male mice (M: 123.8±2 and 119.9±6 mmHg). In female mice, renal-derived human sPRR increased significantly renal AT1R gene expression (F: 1.7±0.5 and 2.6±0.4 2 -ΔΔCT , P<0.05) and stimulated ERK1/2 (F: 0.3±0.0 and 0.6±0.1 AU, P<0.05) suggesting that human sPRR increases blood pressure in female mice likely via AT1R-ERK1/2 pathway activation. In contrast, in male mice, AT1R-ERK1/2 pathway was not up-regulated and renal ACE2 gene expression was significantly increased in RHsPRR males (M: 1.0±0.2 and 3.3±1.1 2 -ΔΔCT , P<0.05). Mechanistically, in male mice, our results indicated that the lack of activation of AT1R-ERK1/2 pathway combined with the increase of ACE2 could have prevented RHsPRR-induced increase in SBP. Together, our data highlighted the contribution of renal human sPRR to blood pressure control in a sex-dependent manner and a new mechanism of blood pressure control that involved the renin angiotensin system.

Abstract 47: Circulating Human Sprr Increased Blood Pressure In Female Mice Fed A Low-fat Diet

Elevated plasma soluble prorenin receptor (sPRR) is associated with essential hypertension and obesity-hypertension in men. Additionally, our laboratory previously found that the infusion of mouse sPRR elevates systolic blood pressure (SBP) in high-fat (HF) fed male mice through activation of the sympathetic nervous system but did not elevate SBP in HF-fed female mice. Interestingly, mouse sPRR infusion increased renal and hepatic angiotensinogen (AGT) and plasma renin concentration in female mice fed a low-fat diet. However, whether sPRR-activates the renin angiotensin system (RAS) and increases blood pressure in low-fat fed female mice remains to be investigated. Additionally, little is known concerning the influence of human sPRR on blood pressure in women. Therefore, we developed a humanized mouse model with high circulating human sPRR. Human sPRR-Myc-tag transgenic mice were bred with mice expressing Alb/Cre recombinase to induce human sPRR release in the circulation. Control and Alb-HsPRR female mice were fed a LF-diet for 8 months (n=11/groups). Body weight and body composition were examined and blood pressure assessed by radiotelemetry. Human sPRR-Myc-tag was detected in the liver of Alb-HsPRR female mice and plasma sPRR levels increased by 50-fold (CTL: 3.6±0.5 ng/ml, HsPRR:190.5±24.4 ng/ml; P<0.05), which validated the humanized mouse model. Elevated circulating human sPRR did not change body weight (CTL: 22.2±0.37, HsPRR: 23.0±0.32 g) or fat mass (CTL: 2.5±0.2, HsPRR: 3.1±0.2 g). Liver-derived human sPRR significantly elevated SBP in Alb-HsPRR compared to control female mice (Night SBP: CTL: 130.5±1.2 mmHg; Alb-HsPRR: 135.9±2 mmHg; P<0.05) and acute injection of AngII exacerbated SBP elevation. Interestingly, the decrease in blood pressure mediated by losartan was not different between Alb-HsPRR and control female mice (Night ΔSBP: CTL: -13.11±2.2 mmHg; Alb-HsPRR: -14.8±2.7 mmHg; P>0.05). Plasma AGT and renin activity were similar between Alb-HsPRR and control female mice. Therefore, whether the local RAS or the sympathetic nervous system are involved in human sPRR-mediated increase of SBP remains to be examined. Altogether, our results suggest an important role of circulating human sPRR in blood pressure control in women.

Abstract MP34: Collecting Duct Cells-derived Human Sprr Impairs The Antihypertensive Effects Of Losartan And Upregulates Erk1/2 And Aqp2 Expression

Recent studies showed that soluble prorenin receptor (sPRR) plays an important role in blood pressure regulation and in water balance. In rodent models, sPRR contributes to AngII production by increasing renin activity, systolic blood pressure (SBP) and aquaporin2 (AQP2)-dependent antidiuretic action. However, there is a gap of knowledge concerning the functional role of locally produced sPRR from the kidney. Therefore, we evaluated the kidney-derived human sPRR role in SBP control and fluid homeostasis. Human sPRR-Myc-tag transgenic mice were bred with mice expressing Hoxb7/Cre to selectively express human sPRR in the collecting duct (RHsPRR). RHsPRR and control (CTL) male mice were fed a standard diet for 10 months (n=8-11/group). Body weight and urine volume were examined and SBP measured by radiotelemetry. Western blot analysis depicted the presence of human sPRR-Myc-tag (28 KDa) in the cortex and medulla of RHsPRR male mice validating the humanized mouse model. Body weight did not change and 24hr-SBP was similar between CLT and RHsPRR mice (128±2 and 122±5 mmHg, respectively). However, the chronic response to losartan treatment was reduced in RHsPRR compared to CTL (ΔSBP: CTL: -9±3; RHsPRR: -5±1 mmHg, P<0.05). Kidney-derived human sPRR did not change GFR (838±75 vs 1088±163 μl/min/100g BW) and urinary vasopressin (0.62±0.21; 0.72±0.20 ng/mg creatinine), while modestly decreasing urine excretion rate by ~40% (CTL: 1.04±0.20; RHsPRR: 0.57±0.25 ml/day). Furthermore, RHsPRR mice had higher AQP2 protein expression in renal cortex (CTL: 0.24±0.07; RHsPRR: 4.11±0.70 AU, P<0.05) and medulla (CTL: 0.11±0.04; RHsPRR: 4.03±1.74 AU, P<0.05) than CTL mice. Kidney-derived human sPRR significantly increased phosphorylation of ERK 1/2 in the cortex compared to CTL (CTL: 5.4±1.0; RHsPRR: 9.2±1.4 AU, P<0.05), an MAPK involved in the regulation of water balance. In addition, RHsPRR mice showed increased plasma osmolality compared to CTL mice (CTL: 349±2; RHsPRR: 357±2 mOsm/kg, P<0.05). Overall, our data suggest that renal human sPRR could contribute to the increase in plasma tonicity by promoting the activation of ERK1/2-AQP2 pathway. Whether this signaling is associated with impaired antihypertensive effects of AT1R blockage remains under investigation.

Abstract MP27: Adipose-derived Human Soluble (Pro)renin Receptor Causes Resistance To Losartan Treatment In High-Fat Diet Male And Female Mice

Obesity, affecting more that 37% of the US, contributes to hypertension. Despite the use of one or more anti-hypertensive treatments, 48% of the hypertensive population remains with resistant hypertension, which prompts the development for new therapeutic targets. We demonstrated that obesity increased the expression of prorenin receptor (PRR) in the adipose tissue and elevated plasma soluble PRR (sPRR). In addition, the infusion of mouse sPRR increased blood pressure in male mice fed high fat-diet (HF); indicating that adipose-derived sPRR could increase circulating sPRR and contribute to hypertension. However, there is a critical gap in the functional role of human sPRR in obesity-hypertension. In this study, we aim to define whether adipose-derived human sPRR contributes to obesity-hypertension. Human sPRR-Myc-tag transgenic mice were bred with mice expressing adiponectin/Cre to selectively express human sPRR in adipocytes (adi-HsPRR). Adi-HsPRR and control littermate (CTL) male and female mice were fed HF-diet for 20 weeks (N=8-15/group). Body weight was assessed weekly and body composition monthly. Blood pressure was measured by telemetry after 15 weeks of diet. Adipose-derived human sPRR did not significantly elevate body weight or fat mass (Male: CTL.18.3±1.0g; adi-HsPRR. 17.5±0.8g. Female: CTL. 15.6±1.5g; adi-HsPRR. 11.9±1.3g; p>0.05). Systolic blood pressure (SBP) significantly increased in HF-fed male and female mice however; adipose-derived human sPRR did not further elevate SBP (24h SBP. Male: CTL. 136.0±1.7 mmHg; adi-HsPRR: 133.4±1.5mmHg; Female: CTL. 131.9±2.8 mmHg; adi-HsPRR: 130.6±3.1 mmHg; p>0.05). Surprisingly, the anti-hypertensive effect of losartan (Los) to lower blood pressure was significantly reduced in adi-HsPRR male and female mice (Male: CTL. ΔSBP: -12.1±1.5 ΔmmHg; adi-HsPRR: -7.8±0.6 ΔmmHg; Female: CTL. ΔSBP: -13.4±1.1 ΔmmHg; adi-HsPRR: -5.7±2.3 ΔmmHg; p<0.05). In 3T3-L1 cells, sPRR significantly increased phosphorylation of ERK1/2, which was not completely blunted by Los indicating that human sPRR could act as a partial agonist of AT1R or activate ERK1/2 independently of AT1R. Our data suggests that adipose-derived sPRR does not stimulate AT1R-mediated contractility, instead impairs Los efficacy.

The prorenin receptor and its soluble form contribute to lipid homeostasis

Obesity is associated with alterations in hepatic lipid metabolism. We previously identified the prorenin receptor (PRR) as a potential contributor to liver steatosis. Therefore, we aimed to determine the relative contribution of PRR and its soluble form, sPRR, to lipid homeostasis. PRR-floxed male mice were treated with an adeno-associated virus with thyroxine-binding globulin promoter-driven Cre to delete PRR in the liver [liver PRR knockout (KO) mice]. Hepatic PRR deletion did not change the body weight but increased liver weights. The deletion of PRR in the liver decreased peroxisome proliferator-activated receptor gamma (PPARγ) and triglyceride levels, but liver PRR KO mice exhibited higher plasma cholesterol levels and lower hepatic low-density lipoprotein receptor (LDLR) and Sortilin 1 (SORT1) proteins than control (CTL) mice. Surprisingly, hepatic PRR deletion elevated hepatic cholesterol, and up-regulated hepatic sterol regulatory element-binding protein 2 (SREBP2) and 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG CoA-R) genes. In addition, the plasma levels of sPRR were significantly higher in liver PRR KO mice than in controls. In vitro studies in HepG2 cells demonstrated that sPRR treatment upregulated SREBP2, suggesting that sPRR could contribute to hepatic cholesterol biosynthesis. Interestingly, PRR, total cleaved and noncleaved sPRR contents, furin, and Site-1 protease (S1P) were elevated in the adipose tissue of liver PRR KO mice, suggesting that adipose tissue could contribute to the circulating pool of sPRR. Overall, this work supports previous works and opens a new area of investigation concerning the function of sPRR in lipid metabolism and adipose tissue-liver cross talk.NEW & NOTEWORTHY Hepatic PRR and its soluble form, sPRR, contribute to triglyceride and cholesterol homeostasis and hepatic inflammation. Deletion of hepatic PRR decreased triglyceride levels through a PRR-PPARγ-dependent mechanism but increased hepatic cholesterol synthesis through sPRR-medicated upregulation of SREBP-2. Our study highlighted a new paradigm of cross talk between the liver and the adipose tissue involving cholesterol and sPRR.

(Pro)renin receptor in the kidney: function and significance

(Pro)renin receptor (PRR), a 350-amino acid receptor initially thought of as a receptor for the binding of renin and prorenin, is multifunctional. In addition to its role in the renin-angiotensin system (RAS), PRR transduces several intracellular signaling molecules and is a component of the vacuolar H⁺-ATPase that participates in autophagy. PRR is found in the kidney and particularly in great abundance in the cortical collecting duct. In the kidney, PRR participates in water and salt balance, acid-base balance, and autophagy and plays a role in development and progression of hypertension, diabetic retinopathy, and kidney fibrosis. This review highlights the role of PRR in the development and function of the kidney, namely, the macula densa, podocyte, proximal and distal convoluted tubule, and the principal cells of the collecting duct, and focuses on PRR function in body fluid volume homeostasis, blood pressure regulation, and acid-base balance. This review also explores new advances in the molecular mechanism involving PRR in normal renal health and pathophysiological states.

Abstract P246: Sex Differences In The Association Between Soluble Prorenin Receptor And Physiological And Cardiometabolic Risk Factors In Healthy Humans Varying In Age And Obesity

The prorenin receptor (PRR), which regulates renin-angiotensin system in multiple tissues, can be cleaved to generate soluble PRR (sPRR) in plasma. sPRR concentrations vary with clinical conditions such as metabolic syndrome, pregnancy, chronic kidney disease and heart failure in humans. However, whether sPRR is associated with aging and healthy obesity in men and women is unknown. We aimed to evaluate if there are sex-specific associations of sPRR with cardiometabolic risk factors among healthy women and men varying in age and obesity. Circulating cardiometabolic, vascular and inflammatory risk factors and sPRR (via ELISA) were measured in unmedicated healthy men (n=55; age 39 ± 16 yrs; BMI 29 ± 4 kg/m2) and women (n=34; age 44 ± 16 yrs; BMI 30 ± 7 kg/m2) at the University of Iowa. Women were classified by menopausal status [pre-menopausal, pre-M (n=18) and post-menopausal, post-M (n=16)]. Independent t -test was used to compare means and pearson correlation was examined. In men, sPRR was not related to age, systolic blood pressure (SBP), BMI, cholesterol or endothelial function (brachial artery flow mediated dilation, FMD), but was correlated with plasma TNFα (r=0.50, P<0.05). sPRR was higher in overweight/obese (BMI ≥ 25 kg/m2) compared with non-obese men (n=48; 10.8 ± 0.4 vs. n=7; 8.3 ± 0.4 ng/ml, P<0.05). In women, sPRR did not correlate with BMI or SBP, but correlated with total cholesterol (r=0.49, P<0.05) and TNFα (r=0.49, P<0.05). sPRR correlated with age in women with a BMI<30 (r=0.54, P<0.05) but not a BMI ≥30 kg/m2. sPRR was significantly higher in post-M compared with Pre-M women independent of obesity or hypertension status (12.1 ± 0.5 vs. 10.1 ± 0.4 ng/ml, P<0.05). sPRR correlated with FMD only in obese women (%FMD: r=-0.50, P<0.05), indicating a relation of sPRR with endothelial dysfunction in obese women. Interestingly, sPRR was significantly higher in Pre-M compared with non-obese men and menopause further exacerbated the difference. In conclusion, sPRR is associated with TNFα in both men and women, but there are sex differences in the relation with BMI, age, cholesterol and endothelial function in humans. sPRR concentrations were higher in post-M compared with pre-M women, suggesting that PRR could contribute to cardiovascular risk in post-M women.

Abstract 10: Mouse Recombinant Soluble PRR-induced Increase Of Blood Pressure Is Sex-dependant In High Fat-fed Mice

Obesity is a major risk factor for hypertension. Although the renin-angiotensin system (RAS) contributes to the sex difference of blood pressure (BP) control, whether the prorenin receptor (PRR) and its soluble form (sPRR) play a role in the sexual dimorphism of BP is not clear. We previously demonstrated that, in high fat (HF)-fed male C57BL/6 mice, the infusion of mouse recombinant sPRR increased systolic blood pressure (SBP) by the sympatho-excitatory effects of leptin on BP. Therefore, in the present study, we aim to address whether mouse recombinant sPRR influences the BP in HF-fed female mice. To test this hypothesis, C57BL/6 female mice were fed a HF diet for 32 weeks and were implanted with radiotelemetry transmitter. After 24 weeks of high fat feeding, female mice (5-6/group) were implanted with osmotic pumps and infused with either saline (veh) or sPRR for 3 to 4 weeks. In contrast to male mice, the infusion of sPRR (30 μg/kg/day) did not change significantly the SBP (24hSBP; veh: 135 ± 7; sPRR: 134 ± 4 mmHg; P>0.05) and the baroreflex sensitivity. The decrease in BP mediated by chlorisondamine treatment was not significantly different between female mice infused with vehicle or sPRR (ΔSBP; veh: -11 ± 9; sPRR: -16 ± 7 mmHg; P>0.05). In addition, sPRR infusion did not affect the bradycardic or tachycardic responses after propranolol or atropine treatment respectively. Moreover, the decrease of SBP induced by losartan was similar in mice infused with vehicle or sPRR (ΔSBP; veh: -9 ± 4; sPRR: -10 ± 3 mmHg; P>0.05). Similar results were obtained using higher dose of sPRR (60 μg/kg/day). In female mice, sPRR infusion did not increase significantly the body weight (veh: 32.7 ± 2.5 g; sPRR: 35.8 ± 4.2 g; P>0.05), the white adipose tissue weight (WAT; veh: 3.0 ± 0.7g; sPRR: 3.7 ± 1.6 g; P>0.05) or circulating leptin levels (veh: 12.0 ± 7.6 ng/ml; sPRR: 15.5 ± 9.5 ng/ml; P>0.05). In conclusion, in contrast to male, female mice are protected from sPRR-induced increase in BP. sPRR did not increase circulating leptin suggesting that sPRR-induced leptin increase is regulated in a sex-dependent manner. Other pathways could participate to the protection against sPRR-induced increase in BP in female mice such as the vasodilator arm of the RAS and/or the hormonal status of the female mice.

Sex-Specific Difference in Adipose Tissue and Blood Pressure in a New Mouse Model Expressing Human Soluble Prorenin Receptor in Adipocytes

Objectives

Sex differences exist in obesity associated with cardiovascular disease; however, underlying mechanisms are not completely understood. Previous studies from our laboratory demonstrated that the prorenin receptor (PRR) and its soluble form (sPRR) contribute to adipogenesis and blood pressure control. The present study aimed to determine whether adipose-sPRR stimulated obesity is associated with hypertension and whether it is sex-dependent.

Methods

Transgenic mice on the C57BL/6 J background were generated expressing the human form of the soluble prorenin receptor (HsPRR) in a Cre-inducible manner. Male mice expressing Cre recombinase under the control of the adiponectin promotor were bred to heterozygote HsPRR/+ female mice to generate mice over-secreting sPRR (adi-HsPRR) and control littermate mice (CTL). The secretion of sPRR in the media doubled in primary adipocytes of adi-HsPRR mice compared to control mice (sPRR. CTL: 3729 ± 805 pg/ml; adi-HsPRR: 6170 ± 1237 pg/ml, P &lt; 0.05) validating the mouse model. Male (CTL = 4; adi-HsPRR = 8) and female mice (CTL = 10; adi-HsPRR = 10) were fed a low-fat (LF) diet or a high-fat diet (HF) for 20 weeks. Body weight was assessed weekly and EchoMRI was examined monthly.

Results

After 20 weeks on LF diet, adi-HsPRR male mice gained significantly more weight than CTL male mice (CTL: 25.1 ± 0.8 g; adi-HsPRR: 29.0 ± 0.8 g P &lt; 0.05), whereas no significant differences in body weights were observed in female mice. The body composition revealed a significant increase of fat mass, specifically in the epidydimal fat (CTL: 0.35 ± 0.04 g; adi-HsPRR: 0.61 ± 0.07 g, P &lt; 0.05), and lean mass of HsPRR male mice compared to CTL male mice. In contrast, female mice exhibited similar body weights (CTL: 20.6 ± 0.3 g; adi-HsPRR: 20.4 ± 0.4 g) and there was no differences of fat mass or lean mass between CTL and adi-HsPRR female mice. The sex-specific mechanism of sPRR on adipogenesis and blood pressure (by radiotelemetry) with LF and HF diet is currently under investigation.

Conclusions

Overall, sPRR stimulated body weight gain and fat mass expansion in male mice but not in female mice suggesting that female mice are protected from sPRR induced-hypertrophic effect.

Funding Sources

R01_HL142969–01 Yiannikouris, PI 07/15/2018–06/30/2022 NIH/NHLBI Title: The role of soluble prorenin receptor in hypertension associated with obesity Role: Ph.D Graduate Student.

A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

Mast cells in asthma--state of the art

Mast cells (MCs) play a central role in tissue homoeostasis, sensing the local environment through numerous innate cell surface receptors. This enables them to respond rapidly to perceived tissue insults with a view to initiating a co-ordinated programme of inflammation and repair. However, when the tissue insult is chronic, the ongoing release of multiple pro-inflammatory mediators, proteases, cytokines and chemokines leads to tissue damage and remodelling. In asthma, there is strong evidence of ongoing MC activation, and their mediators and cell-cell signals are capable of regulating many facets of asthma pathophysiology. This article reviews the evidence behind this.

Polymerase chain reaction for diagnosis of genital herpes: a missed opportunity?

This study audited the utilization of herpes simplex virus polymerase chain reaction (HSV PCR) in the investigation of recurrent anogenital ulceration at the Mortimer Market Centre. Clinic guidelines for use of HSV PCR were modified in April 2003 to expand PCR use. Ninety-six case-notes belonging to patients presenting with recurrent anogenital ulceration between 1 April and 16 October 2003 were reviewed and 59 were suitable for inclusion. Details of the investigations carried out at each visit were recorded. HSV PCR was used according to guidelines in eight of the 59 cases studied. This audit showed under-utilization of HSV PCR testing with poor adherence to clinic guidelines when cases of suspected recurrent genital herpes were investigated. This led to under-diagnosis and delay in diagnosis. This audit stresses the importance of informing all clinical staff of the improved sensitivity and relative affordability of HSV PCR compared with HSV tissue culture.

Is vaginal microscopy an essential tool for the management of women presenting with vaginal discharge?

Point-of-care microscopy is the gold standard for the diagnosis of vaginal discharge in genitourinary (GU) medicine clinics but not used in primary care settings and reproductive health clinics to which many patients present. In our GU medicine clinic setting, we conducted an audit to assess the utility of microscopy of vaginal secretions versus clinical diagnosis alone for the differential diagnosis of uncomplicated lower vaginal infections. Clinical diagnosis (including pH) of bacterial vaginosis had a sensitivity between 85% and 88% at two clinic sites. Our results suggest that it may be safe and more cost-effective to restrict vaginal microscopy to a subgroup of women presenting with vaginal discharge.

HIV voluntary counselling and testing for African communities in London: learning from experiences in Kenya

OBJECTIVES

To explore the feasibility and acceptability of translating a successful voluntary counselling and testing (VCT) service model from Kenya to African communities in London.

METHODS

Qualitative study with focus group discussions and a structured workshop with key informants. Five focus group discussions were conducted in London with 42 participants from 14 African countries between August 2006 and January 2007. A workshop was held with 28 key informants. Transcripts from the group discussions and workshop were analysed for recurrent themes.

RESULTS

Participants indicated that a community-based HIV VCT service would be acceptable to African communities in London, but also identified barriers to uptake: HIV-related stigma, concerns about confidentiality, and doubts about the ability of community-based services to maintain professional standards of care. Workshop participants highlighted three key requirements to ensure feasibility: (a) efficient referrals to sexual health services for the newly diagnosed; (b) a locally appropriate testing algorithm and quality assurance scheme; (c) a training programme for VCT counsellors.

CONCLUSIONS

Offering community-based VCT with rapid HIV tests appears feasible within a UK context and acceptable to African communities in London, provided that clients' confidentiality is ensured and appropriate support is given to the newly diagnosed. However, the persistence of concerns related to HIV-related stigma among African communities suggests that routine opt-out testing in healthcare settings may also constitute an effective approach to reducing the proportion of late diagnoses in this group. HIV service models and programmes from Africa constitute a valuable knowledge base for innovative interventions in other settings, including developed countries.

Behaviour change in clients of health centre-based voluntary HIV counselling and testing services in Kenya

OBJECTIVE

To explore behaviour change, baseline risk behaviour, perception of risk, HIV disclosure and life events in health centre-based voluntary counselling and testing (VCT) clients.

DESIGN AND SETTING

Single-arm prospective cohort with before-after design at three (one urban and two rural) government health centres in Kenya; study duration 2 years, 1999-2001.

SUBJECTS

Consecutive eligible adult clients.

MAIN OUTCOME MEASURES

Numbers of sexual partners, partner type, condom use, reported symptoms of sexually transmitted infection, HIV disclosure and life events.

RESULTS

High rates of enrollment and follow-up provided a demographically representative sample of 401 clients with mean time to follow-up of 7.5 months. Baseline indicators showed that clients were at higher risk than the general population, but reported a poor perception of risk. Clients with multiple partners showed a significant reduction of sexual partners at follow-up (16% to 6%; p<0.001), and numbers reporting symptoms of sexually transmitted infection decreased significantly also (from 40% to 15%; p<0.001). Condom use improved from a low baseline. Low rates of disclosure (55%) were reported by HIV-positive clients. Overall, no changes in rates of life events were seen.

CONCLUSION

This study suggests that significant prevention gains can be recorded in clients receiving health centre-based VCT services in Africa. Prevention issues should be considered when refining counselling and testing policies for expanding treatment programmes.

Trends in bloodstream infections among human immunodeficiency virus-infected adults admitted to a hospital in Nairobi, Kenya, during the last decade

Bloodstream infections are a frequent complication in human immunodeficiency virus (HIV)-infected adults in Africa and usually associated with a poor prognosis. We evaluated bloodstream infections across a decade in 3 prospective cross-sectional surveys of consecutive medical admissions to the Kenyatta National Hospital, Nairobi, Kenya. Participants received standard clinical care throughout. In 1988-1989, 29.5% (28 of 95) of HIV-positive patients had bloodstream infections, compared with 31.9% (46 of 144) in 1992 and 21.3% (43 of 197) in 1997. Bacteremia and mycobacteremia were significantly associated with HIV infection. Infections with Mycobacterium tuberculosis, non-typhi species of Salmonella (NTS), and Streptococcus pneumoniae predominated. Fungemia exclusively due to Cryptococcus neoformans was uncommon. Clinical features at presentation remained similar. Significant improvements in the survival rate were recorded among patients with NTS bacteremia (20%-83%; P<.01) and mycobacteremia (0%-73%; P<.01). Standard clinical management can improve outcomes in resource-poor settings.

Human growth factor receptor bound 14 binds the activated insulin receptor and alters the insulin-stimulated tyrosine phosphorylation levels of multiple proteins

To identify proteins interacting in the insulin-signaling pathway that might define new pathways or regulate existing ones, we have employed the yeast two-hybrid system. In a two-hybrid screen of a human liver cDNA library, we identified the human growth factor receptor bound 14 (hGrb14) adaptor protein as a partner of the activated insulin receptor. Additional analysis of the insulin receptor--hGrb14 interaction in the yeast two-hybrid system revealed that the SH2 domain of hGrb14 was not the sole region involved in binding the activated insulin receptor. The insulin-stimulated interaction between hGrb14 and the insulin receptor was also observed in different mammalian cultured cell lines. This association was detected at 1 min of insulin stimulation and was maximal at 10 nM and greater concentrations of insulin. Chinese hamster ovary cells stably expressing the insulin receptor (CHO-IR) and hGrb14 were used to examine the effects of hGrb14 overexpression on insulin-stimulated tyrosine phosphorylation of proteins; in general, increasing levels of hGrb14 expression resulted in a reduction in tyrosine phosphorylation. This decrease was demonstrated for the specific proteins src homology-containing and collagen-related protein (Shc), insulin receptor substrate-1 (IRS-1), and Downstream of tyrosine Kinase (Dok). The broad effects of hGrb14 overexpression on insulin-stimulated tyrosine phosphorylation suggest that it acts early in the insulin-signaling pathway.

Synthesis and growth inhibitory properties of glucosamine-derived glycerolipids

[figure: see text] 2-Amino C-glycerolipid 1b was synthesized by using the Ramberg-Bäcklund rearrangement as the key step. beta-C-Glycerolipid 1b exhibits in vitro antiproliferative effects strikingly similar to those of O-glycoside analogue 1a.

The changing impact of HIV/AIDS on Kenyatta National Hospital, Nairobi from 1988/89 through 1992 to 1997

OBJECTIVE

Consequences of the growing HIV/AIDS epidemic for health services in sub-Saharan Africa remain poorly defined. Longitudinal data from the same centre are scarce. We aimed to describe the impact of a rapidly rising HIV/AIDS disease burden on an urban hospital over the last decade.

DESIGN AND SETTING

Cross-sectional observational study in 1997, compared to similar data from 1988/89 and 1992. The study was carried out in the Kenyatta National Hospital, Nairobi, Kenya.

METHOD

Consecutive adult medical patients were enrolled on admission and then followed up until death or discharge. The main outcome measures were clinical stage, HIV status, bacteraemia, length of stay, bed occupancy, final diagnosis and outcome of hospital admission.

RESULTS

In 1997, 518 patients, 493 with HIV serology, were enrolled: HIV prevalence was 40.0%, bed occupancy 190%, the mean length of stay 9.5 days (SD 12) and overall mortality 18.5%. The mean number of HIV-positive admissions per day steadily rose from 4.3 [95% confidence interval (CI), 0.6] patients in 1988/89, through 9.6 (95% CI, 1.4) in 1992, to 13.1 (95% CI, 2.8) or 13.9 adjusted for those enrolled without HIV serology in 1997. In contrast the mean number admitted with clinical AIDS, 1.7 in 1988/89 and 3.3 in 1992, fell to 2.6 cases per day in 1997. With HIV-negative admissions increasing by 37% and bed occupancy nearly doubling in 1997, HIV prevalence appeared to be stabilizing (19 then 39 and 40% respectively). Over time fewer HIV-infected patients were bacteraemic (26, 24 and 14%; P < 0.01); had clinical AIDS (39, 34 and 24% respectively; P < 0.01); or died (36, 35 and 22.6%; P < 0.02). HIV-negative mortality, 14% in 1988/89, rose to 23% in 1992 but fell to 15% in 1997. The mean length of hospital stay (9.5-10 days) did not differ according to HIV status nor did it change across the decade.

CONCLUSION

The HIV/AIDS disease burden in Kenyatta National Hospital medical wards has risen inexorably over the last decade. Most recently, the number of HIV-uninfected patients has also risen, leading to bed occupancy figures of 190%. Despite overcrowding and irrespective of HIV status, in-patient mortality has fallen. Time trends suggest fewer clinical AIDS patients are presenting for hospital care, implying a rising community burden of chronic HIV/AIDS disease. Although widely predicted, it is not inevitable that medical services in urban African hospitals dealing with large volumes of HIV/AIDS disease, will collapse or become overwhelmed with chronic, end-stage disease and death.

The effect of fenofibrate treatment on endothelium-dependent relaxation induced by oxidative modified low density lipoprotein from hyperlipidemic patients

The objective of the research project was to investigate whether fenofibrate treatment may alter the biochemical content of the oxidized LDL and consequently its ability to impair the endothelium-dependent relaxation in hyperlipidemic patients. We hypothesized that fenofibrate treatment of hyperlipidemic patients may attenuate the ability of their oxidized LDL to impair the endothelium-dependent relaxation of the blood vessels as a consequence of fenofibrate-induced changes to the content and composition of lysoPC in the LDL molecule. Hyperlipidemic patients (Type IIb and Type IV) were recruited from the Lipid Clinic, HSC, Winnipeg, Canada, for this study. A blood sample was taken immediately after the recruitment, a second sample was taken after 6 weeks of dietary treatment, and a third sample was taken after 8 weeks of fenofibrate treatment. LDL was isolated from the plasma and oxidized by copper sulfate. Fenofibrate was shown to be highly effect in the reduction of total cholesterol, LDL cholesterol and triglycerides in these patients. Fenofibrate treatment also caused the attenuation of impairment of endothelium-dependent relaxation by the oxidized LDL from these patients. A slight reduction of lysophosphatidylcholine level was also found in the oxidized LDL of the fenofibrate treated patients, relative to LDL isolated after dietary treatment. In addition there were no changes in the fatty acid levels of the lysophosphatidylcholine isolated from LDL. Taken together, our results suggest that while the reduced lysophosphatidylcholine levels may contribute to the attenuated impairment of the endothelium-dependent relaxation of the aortic ring, other unidentified factors impacted by fenofibrate are likely to contribute to the attenuated effects.

Convergent C-glycolipid synthesis via the Ramberg-Bäcklund reaction: active antiproliferative glycolipids

[formula: see text] A novel methodology has been developed, employing the Ramberg-Bäcklund rearrangement and ionic hydrogenation to synthesize C-glycosides with high stereoselectivity at the anomeric center. The C-glycolipid 14b exhibits antiproliferative properties similar to those of O-glycoside analogue 14a.

Decreased sensitivity to 1-O-octadecyl-2-O-methyl-glycerophosphocholine in MCF-7 cells adapted for serum-free growth correlates with constitutive association of Raf-1 with cellular membranes

We have previously shown that inhibition of MCF-7 cell proliferation by 1-O-octadecyl-2-O-methyl-glycerophosphocholine (ET-18-OCH3) is linked to a drug-induced decrease in membrane Raf-1 levels and the subsequent inhibition of mitogen-activated protein (MAP) kinase activation in response to growth factor stimulation. We now report that adaptation of MCF-7 cells for growth in a serum-free formulation results in decreased sensitivity to growth inhibition by ET-18-OCH3. The decrease in ET-18-OCH3 sensitivity occurred progressively during the adaptation process and correlated with the presence of increasing amounts of inactive Raf-1 that stably associated with MCF-7 cell membranes. ET-18-OCH3 sensitivity could be restored by growing the adapted cells in serum-containing medium, which resulted in the loss of membrane-associated Raf-1. In human normal mammary epithelial cells, which are insensitive to ET-18-OCH3, Raf-1 was also associated with membranes in quiescent cells. In both cell types, incubation with ET-18-OCH3 had no effect on the membrane-Raf-1 levels, suggesting that ET-18-OCH3-induced reduction of Raf-1 levels in growth factor-stimulated MCF-7 cells is due to inhibition of Raf translocation. The activation and termination of the MAP kinase pathway in response to growth factors in the adapted MCF-7 cells and HNME cells occurred without changes to membrane Raf-1 levels. Because membrane translocation is not required to activate Raf in these cells, inhibition of Raf translocation by ET-18-OCH3 subsequent to cell stimulation has no effect on the activation of the membrane-bound Raf and, consequently, the activation of the MAP kinase pathway. The ability of the cells to activate the MAP kinase pathway in the presence of the drugs enables them to resist the growth-inhibitory effects of the drug, leading to the observed ET-18-OCH3 insensitivity of the cells.

Effects of a water-soluble antitumor ether phosphonoinositide, D-myo-inositol 4-(hexadecyloxy)-3(S)-methoxybutanephosphonate (C4-PI), on inositol lipid metabolism in breast epithelial cancer cell lines

We have demonstrated previously that D-myo-inositol 4-(hexadecyloxy)-3(S)-methoxybutanephosphonate (C4-PI), an isosteric phosphonate analog of phosphatidylinositol developed to inhibit inositol lipid metabolism, was unable to inhibit phosphatidylinositol (PI) 3-kinase activity. We now report the effects of the compound on other aspects of inositol metabolism. We demonstrated that C4-PI inhibits the activity of purified recombinant PI-phospholipase C-beta (PLC-beta) at all concentrations tested; it enhanced the activity of PI-PLC-gamma and PI-PLC-delta at low concentrations (10 microM), while severely inhibiting their activities at higher concentrations. In the breast cancer cell lines MCF-7 (estrogen receptor positive) and MDA-MB-468 (estrogen receptor negative), C4-PI had no effect on the uptake of D-myo-inositol but severely inhibited its incorporation into PI. In spite of the drastic decrease in PI synthesis, C4-PI did not affect the levels of inositol incorporated into phosphatidylinositol 4,5-bisphosphate (PIP2) in the cells. In vitro assays showed that C4-PI inhibited PI synthase activity (inhibition of 35% at 50 microM) but had little effect on PI 4-kinase activity (inhibition of 13% at 150 microM). C4-PI inhibited the proliferation of MCF-7 and MDA-MB-468 cell lines with IC(50) values of 12 and 18 microM. Taken together, the results suggest that the accumulation of [3H]inositol in PIP2 in cells incubated with C4-PI may be due to the inhibition of PIP2 hydrolysis in the cells with no effect on its synthesis. The role of these C4-PI-induced effects in the mechanism of growth inhibition by C4-PI remains to be established.

Development of brief pictorial instruments for assessing spirituality in primary care

The relationship between spirituality and health is an emerging area of study. However, spirituality assessment instruments with clinical utility for busy health care practices are lacking. The article describes research directed at developing and validating brief pictorial measures of spirituality as instruments to measure the relationship between reported spirituality and health. The instruments presented are patterned after the Dartmouth Medical School Primary Care Cooperative (COOP) charts. The charts also provide a nonthreatening way to enhance communication between patients and physicians in this important area.

CQI teamwork: reevaluate, restructure, renew

Here, a continuous quality improvement (CQI) team evaluates and streamlines hospital processes, and impacts admission and transportation, medication administration, and morale.

The relationship between a patient's spirituality and health experiences

BACKGROUND AND OBJECTIVES

The relationship between spirituality and health is a new frontier in medicine. This study is a preliminary investigation into the relationship between a patient's experience of overall health, physical pain, and intrinsic spirituality.

METHODS

We used a stratified, random sample of 462 patients at a family practice residency clinic. The Index of Core Spiritual Experiences (INSPIRIT) measured intrinsic spirituality, and Dartmouth Primary Care Cooperative Charts measured overall health and pain. Pearson correlations tested the association between health, pain, and spirituality. Patient scores on the INSPIRIT were then placed into three groups (high, medium, and low levels of intrinsic spirituality). ANOVA tested for significant differences in health and pain.

RESULTS

We collected information from 442 of the patients surveyed (95%). We found significant correlation between patient health and spirituality. Significant differences were also found in both overall health and physical pain, based on the three levels of spirituality. Gender differences were only significant for overall health, not for patient pain.

CONCLUSIONS

Our results suggest an association between intrinsic spirituality and a patient's experience of health and pain. Assessment of spirituality may be important for family physicians to consider as a supplement to patient interviews.

Glycosylated antitumor ether lipids are more effective against oncogene-transformed fibroblasts than alkyllysophospholipids

We have investigated the antiproliferative effects of different types of antitumor ether lipids (AELs) against non-transformed and transformed fibroblasts. The compounds examined were choline phosphate-containing alkyllysophospholipids (1-O-octadecyl-2-O-methyl glycerophosphocholine (ET18-OCH3), 2'-(trimethylammonio)ethyl 3-(hexadecyloxy)-2-(methoxymethyl)propylphosphate (oxo-BM 41.440), 2'-(triethylammonio)ethyl 4-(hexadecyloxy)-3-methoxybutane phosphonate (ET16-OCH3-phosphonocholine)), and glycosylated ether-linked diglycerides (1-O-hexadecyl-2-O-methyl-3-S-(beta-D-1'-thioglucopyranosyl-sn-gly cerol) [ET16-OCH3-beta-thio-Glc] and 1-O-hexadecyl-2-O-methyl-3-O-(2'amino-2'-deoxy-beta-D-glucopyranosyl)-sn -glycerol (ET16-OCH3-Gln)). The choline phosphate-containing alkyllysophospholipids (ALPs) had little or moderate effect on the proliferation and none on the viability of NIH 3T3 clone 7, and sublines transformed by raf (NIH/9IV #5), fes (Fes 1), src (Src 1) and mos (Mos 1) oncogenes. The glycosylated ether-linked diglycerides were more effective than the choline phosphate-containing ALPs. Of the two ether-linked diglycerides, ET16-OCH3-beta-thio-Glc did not affect the viability of the cells at any of the concentrations examined while ET16-OCH3-Gln was cytotoxic to all the transformed cell lines at concentrations equal to or greater than 9 microM. The IC50 for ET16-OCH3-Gln was 6.4 microM for Mos 1, 6.5 microM for NIH/9IV #5, 7.5 microM for Src 1, 8.2 microM for Fes 1 and 8.4 microM for NIH 3T3 clone 7. These results suggest that the ether-linked diglycerides may be more effective against fibrosarcomas than the cholinephosphate containing ALPs. Also, with the exception of ET16-OCH3-Gln there was no significant difference in the effect of the compounds on the transformed and untransformed cell lines, suggesting that the selectivity displayed by AELs may depend on both the type of compound and transformation in the cell.

Heterogeneity of polyclonal IgE characterized by differential charge, affinity to protein A, and antigenicity

Functional and physical heterogeneity of polyclonal IgE has been reported. Extremely low serum concentrations of IgE have limited the study of these important differences. We have purified polyclonal dog IgE and developed polyclonal and monoclonal (mAb C2) anti-dog IgE antibodies. In this study chromatofocusing of dog IgE revealed two biologically active IgE fractions: IgE1 eluted at pH 5.0, and IgE2 eluted at pH 4.7. The two IgE subforms (IgEs) exhibited typical IgE characteristics: positive in the 48-hour passive cutaneous anaphylaxis response, heat-labile, identical molecular weight, and reactive to polyclonal anti-dog IgE. However, the two IgEs were found to be significantly heterogeneous. IgE1 bound to protein A and did not react with mAb C2 in ELISA and isoelectric focusing-immunoblotting, whereas IgE2 did not bind to protein A and reacted with mAb C2. Further, in sodium dodecylsulfate-polyacrylamide gel electrophoresis and immunoblotting, IgE2, but not IgE1, reacted with seven well-defined mAb anti-human IgE antibodies and an mAb anti-mouse IgE antibody, even though both IgE1 and IgE2 reacted with polyclonal anti-human and anti-mouse IgE. Neuraminidase or endoglycosidase treatment did not abolish the differential antigenicity and charge of IgE1 and IgE2, although the antigenicity of IgE2 was significantly reduced after incubation with endoglycosidase. These data suggest that carbohydrate moieties are not involved in the observed differences in antigenicity and charge and that the two IgE molecules represent distinct isotypes. In studies with seven purified IgE fractions obtained from different ragweed-allergic dogs, the distribution of ragweed IgE2 varied 200-fold, whereas ragweed total IgE levels varied only fourfold. This raises the possibility of a relationship between different IgEs and the allergic response.

1-O-Octadecyl-2-O-methylglycerophosphocholine inhibits protein kinase C-dependent phosphorylation of endogenous proteins in MCF-7 cells

Studies with leukaemic cells, based primarily on in vitro assays, have suggested that antitumour ether lipids have only a moderate effect on protein kinase C (PKC) activity, and, furthermore, inhibition of PKC is unlikely to be involved in the mechanism of inhibition of cell proliferation by these compounds. To determine if this is also the case for epithelial cancer cells, we examined the effect of 1-O-octadecyl-2-O-methylglycerophosphocholine (ET18-OCH3) on PKC-induced phosphorylation of endogenous proteins in MCF-7 cells under incubation conditions where the drug inhibited cell proliferation. As expected, stimulation of quiescent 32P-labelled MCF-7 cells with 1 microM PMA resulted in the phosphorylation of a number of proteins. The PMA-induced phosphorylation of the proteins was abolished by preincubation of the cells with Ro 31-8220 (5 microM) for 20 min, or 10 microg/ml ET18-OCH3 for 3 h before stimulation with PMA. Thus under incubation conditions where ET18-OCH3 inhibited the proliferation of MCF-7 cells, the ether lipid potently inhibited the activity of PKC in intact cells. This inhibition was unlikely to be due to the effect of the compound on PKC translocation since there was little effect of ET18-OCH3 on the translocation of the alpha, gamma and epsilon species of PKC. These results suggest that a role for the inhibition of PKC activity by ET18-OCH3 in the mechanism of inhibition of cell proliferation by ET18-OCH3 cannot yet be discounted in epithelial cancer cells. In addition, we also observed that ET18-OCH3 enhanced the phosphorylation of selected proteins under basal unstimulated conditions. Although some of these proteins were also observed to be phosphorylated in response to PMA stimulation, the phosphorylation induced by ET18-OCH3 was not inhibited by Ro 31-8220, indicating that this was not mediated by PKC.

Enantioselective synthesis and antiproliferative properties of an ilmofosine analog, 2'-(trimethylammonio)ethyl 3-(hexadecyloxy)-2-(methoxymethyl)propyl phosphate, on epithelial cancer cell growth

An asymmetric synthesis of the 1-alkyloxy analog of the thioether phosphocholine ilmofosine (BM 41.440, rac-1), 2'-(trimethylammonio)ethyl 3-(hexadecyloxy)-2-(methoxymethyl)propyl phosphate (2), is described. Stereoselectivity was obtained in an asymmetric hydroboration-oxidation sequence carried out on a 2,2-disubstituted 1-alkene, 3-(hexadecyloxy)-2-(methoxymethyl)-1-propene (9), which was prepared by starting with either ethyl acrylate or ethyl alpha-(hydroxymethyl)acrylate (3). (R)- and (S)-2 and rac-1 were highly effective in inhibiting the proliferation of the breast adenocarcinoma cell line MCF-7 (IC50, 2 microM), moderately effective against A549 (non-small-cell lung adenocarcinoma) (IC50, 8-10 icroM), and less effective against A427 (large cell lung carcinoma) (IC50, approximately 20 microM). The in vitro cytotoxicity against the three epithelial cancer cell lines was independent of the configuration about C-2 of the glycerol backbone of 2 and was also not altered by substitution of oxygen for sulfur in the sn-1 ether linkage of ilmofosine.

1-O-octadecyl-2-O-methyl-glycerophosphocholine inhibits the transduction of growth signals via the MAPK cascade in cultured MCF-7 cells

1-O-Octadecyl-2-O-methyl-glycerophosphocholine (ET18-OCH3) is an ether lipid with selective antiproliferative properties whose mechanism of action is still unresolved. We hypothesized that since ET18-OCH3 affects a wide variety of cells, its mechanism of action was likely to involve the inhibition of a common widely used pathway for transducing growth signals such as the mitogen-activated protein kinase (MAPK) cascade. To test this, we established conditions whereby quiescent MCF-7 cells took up ET18-OCH3 in sufficient quantities that inhibited cell proliferation subsequent to the addition of growth medium and examined the activation of components of the MAPK cascade under these conditions. ET18-OCH3 inhibited the sustained phosphorylation of MAPK resulting in a decrease in the magnitude and duration of activation of MAPK in cells stimulated with serum or EGF. ET18-OCH3 had no effect on the binding of EGF to its receptors, their activation, or p21ras activation. However, an interference in the association of Raf-1 with membranes and a resultant decrease in Raf-1 kinase activity in membranes of ET18-OCH3-treated cells was observed. ET18-OCH3 had no direct effect on MAPK or Raf-1 kinase activity. A direct correlation between ET18-OCH3 accumulation, inhibition of cell proliferation, Raf association with the membrane, and MAPK activation was also established. These results suggest that inhibition of the MAPK cascade by ET18-OCH3 as a result of its effect on Raf-1 activation may be an important mechanism by which ET18-OCH3 inhibits cell proliferation.

Synthesis of ether-linked analogues of lysophosphatidate and their effect on the proliferation of human epithelial cancer cells in vitro

To investigate whether lysophosphatidate analogues of alkyllysophospholipids were antiproliferative we synthesized three new ether-linked analogues of lysophosphatidic acid and investigated their antiproliferative activity on epithelial cancer cell lines derived from different tissues. The antiproliferative effects of the compounds on MCF-7 and T47D (breast), A549 and A427 (lung), A498 (kidney), SK-N-SH and SK-N-MC (neuroblastoma), and DU145 (prostate) cells were compared with the ability of 1-O-octadecyl-2-O-methyl-glycero-3-phosphocholine, the archetypic alkyllysophospholipid, to inhibit the proliferation of all the cell lines. 1-O-Hexadecyl-2-O-methyl-sn-glycero-3-phosphate and 4-thiohexadecyl-3(S)-O-methoxybutane-4-phosphate were unable to inhibit the proliferation of any of the cells to any degree, while slightly enhancing the proliferation of DU145 cells. In contrast 4-O-hexadecyl-3(S)-O-methoxybutanephosphonate was a potent antiproliferative agent that was on the whole more active than 1-O-octadecyl-2-O-methyl-glycero-3-phosphocholine. Since 1-Oleoyl-2-lyso-phosphatidate (LPA) was non-mitogenic in all the cell lines except the neuroblastoma line SK-N-SH, it is unlikely that the inhibition of cell proliferation by 4-O-hexadecyl-3(S)-O-methoxybutanephosphonate was a consequence of perturbation of cellular response to the mitogenic effects of LPA.

Synthesis and evaluation of the antiproliferative effects of 1-O-hexadecyl-2-O-methyl-3-O-(2'-acetamido-2'-deoxy-beta-D- glucopyranosyl)-sn-glycerol and 1-O-hexadecyl-2-O-methyl-3-0- (2'-amino-2'-deoxy-beta-D-glucopyranosyl)-sn-glycerol on epithelial cancer cell growth

Two ether glucosyl diglyceride analogs were synthesized, and their antiproliferative activity against four epithelial cancer cell lines was evaluated. 1-O-Hexadecyl-2-O-methyl-3-O-(2'-acetamido-2'-deoxy-beta-D- glucopyranosyl)-sn-glycerol (4) was synthesized by reaction of 2-acetamido-2-deoxy-3,4,6-tri-O-acetyl-alpha-D-glucopyranosyl chloride with 1-O-hexadecyl-2-O-methyl-sn-glycerol followed by deacetylation by methanolic hydrolysis. The N-acetyl group of 4 was removed by hydrolysis with ethanolic potassium hydroxide to form 1-O-hexadecyl-2-O-methyl-3-O-(2'-amino-2'-deoxy-beta-D-glucopyranosyl)- sn-glycerol (5). Compounds 4 and 5 inhibited the proliferation of MCF-7, A549, A427, and T84 cancer cell lines. The IC(50) values for 5 ranged from 6.5 to 12.2 microM, whereas 4 was more effective against A549 cells (IC(50) 9 microM) than against MCF-7 (IC(50) 17 microM) and A427 (IC(50) 25 microM) cells and was inactive against T84 cells. Under identical incubation conditions, compounds 4 and 5 were potent inhibitors of the proliferation of OVCAR-3 cells with IC(50) values of 12 and 4 microM, respectively, whereas ET-18-OCH(3), hexadecylphosphocholine, and erucylphosphocholine had IC(50) values of 24, >30, and >30 microM, respectively. The cell-inhibitory profile of these ether-linked glucosyl diglycerides strengthens the hypothesis that such glycolipids represent a distinct group of antitumor ether lipids, having antineoplastic activities that differ from the well-known alkylphosphocholines and alkyllysophospholipids.

Evidence for receptor and G-protein regulation of a phosphatidylethanolamine-hydrolysing phospholipase A1 in guinea-pig heart microsomes: stimulation of phospholipase A1 activity by DL-isoprenaline and guanine nucleotides

While evidence has been presented for the receptor-mediated activation of phospholipases A2, C and D, the activation of phospholipase A1 subsequent to receptor activation has not been established. Phospholipase A1-catalysed hydrolysis of 1-palmitoyl-2-linoleoyl-glycerophosphoethanolamine (GPE) by guinea-pig heart microsomes was stimulated 40-60% by isoprenaline. This isoprenaline-mediated increase in activity was blocked by propranolol and butoxamine, a specific beta 2-adrenergic antagonist, but not by atenolol, a specific beta 1-adrenergic antagonist. Neither clonidine nor phenylephrine, alpha 1- and alpha 2-adrenergic agonists respectively, had a stimulatory effect on the hydrolysis of the PE substrate. Guanosine 5'(-)[gamma-thio]triphosphate (GTP[S]) and guanosine 5'(-)[beta,gamma-imido]triphosphate, but not guanosine 5'(-)[beta-thio]diphosphate (GDP[S]) or adenosine 5'(-)[gamma-thio]triphosphate, stimulated the hydrolysis of 1-palmitoyl-2-linoleoyl-GPE by phospholipase A1. GDP[S] inhibited the isoprenaline-mediated stimulation of phospholipase A1 activity. Phospholipase A1 hydrolysis of 1-palmitoyl-2-linoleoyl-GPE was not dependent on cations; however, the stimulatory effects of isoprenaline and GTP[S] on the hydrolytic activity were abolished by cation chelators. The above data suggest that phospholipase A1 activity in guinea-pig heart microsomes is activated by the binding of isoprenaline to beta 2-adrenergic receptors. Furthermore the stimulation of phospholipase A1 activity by the agonist may be mediated via activation of G-proteins.