Biomedical subjects
Friedrich C Luft
Publications and source records attributed to Friedrich C Luft.
A splice mutation in a Syrian autosomal recessive hypercholesterolemia family causes a two-nucleotide deletion of mRNA.
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Glucose-induced TGF-beta1 and TGF-beta receptor-1 expression in vascular smooth muscle cells is mediated by protein kinase C-alpha.
Sclerosis and increased matrix expression in diabetes are mediated by glucose-induced transforming growth factor (TGF)-beta1 expression. The intracellular effects of high glucose occur at least in part by way of protein kinase C (PKC). We previously described a role for PKC-alpha in glucose-induced permeability. We now investigated the hypothesis that glucose-induced expression of TGF-beta1 and its receptors (TGF-beta-R1 and -R2) are mediated by activation of this PKC isoform. TGF-beta1 and TGF-beta-R expressions were determined in vascular smooth muscle cells (VSMCs) by immunocytochemistry and Western blotting. PKC isoforms were assessed by confocal microscopy. PKC isoforms were inhibited with antisense oligodeoxynucleotides. PKC-alpha was upregulated by overexpression or microinjection. High glucose (20 mmol/L) increased VSMC TGF-beta1 and TGF-beta-R1 expression but not TGF-beta-R2 expression. PKC inhibitors and specific PKC-alpha downregulation by antisense treatment prevented this effect, whereas antisense treatment against PKC-beta, -epsilon, and -zeta had no influence. PKC-alpha overexpression increased TGF-beta1 and TGF-beta-R1 expression but not TGF-beta-R2 expression. PKC-alpha microinjection into individual VSMCs also increased TGF-beta1 and TGF-beta-R immunofluorescence. Last, VSMCs from PKC-alpha-deficient mice did not respond to high glucose compared with VSMCs from wild-type mice. We propose that high glucose-induced TGF-beta1 and TGF-beta-R1 expression is mediated by PKC-alpha. Our findings suggest an autocrine feedback mechanism and a possible role for PKC-alpha in diabetic vascular disease.
Transducing proteins to manipulate intracellular targets.
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Osmotically inactive skin Na+ storage in rats.
Compared with age-matched men, women are resistant to the hypertensive effects of dietary NaCl; however, after menopause, the incidence of salt-sensitive hypertension is similar in women and men. We recently suggested that osmotically inactive Na+ storage contributes to the development of salt-sensitive hypertension. The connective tissues, including those immediately below the skin that may serve as a reservoir for osmotically inactive Na+ storage, are affected by menopause. We tested the hypothesis that ovariectomy (OVX) might reduce osmotically inactive Na+ storage capacity in the body, particularly in the skin. Male, female-fertile, and female OVX Sprague-Dawley (SD) rats were fed a high (8%)- or low (0.1%)-NaCl diet. The groups received the diet for 4 or 8 wk. At the end of the experiment, subgroups received 0.9% saline infusion and urinary Na+ and K+ excretion was measured. Wet and dry weight (DW), water content in the body and skin, total body Na+ (rTBNa+) and skin Na+ (rSKNa+) content were measured relative to DW by desiccation and dry ashing. There were no gender differences in osmotically inactive Na+ storage in SD rats. All SD rats accumulated Na+ if fed 8% NaCl, but rTBNa+ was lower in OVX rats than in fertile rats on a low (P < 0.001)- and a high (P < 0.05)-salt diet. OVX decreased rSKNa+ (P < 0.01) in the rats. A high-salt diet led to Na+ accumulation (DeltaSKNa+) in the skin in all SD rats. Osmotically inactive skin Na+ accumulation was approximately 66% of DeltaSKNa+ in female and 82% in male-fertile rats, but there was no osmotically inactive Na+ accumulation in OVX rats fed 8% NaCl. We conclude that skin is an osmotically inactive Na+ reservoir that accumulates Na+ when dietary NaCl is excessive. OVX leads to an acquired reduction of osmotically inactive Na+ storage in SD rats that predisposes the rats to volume excess despite a reduced Na+ content relative to body weight.
Hydroxymethylglutaryl coenzyme A reductase inhibition reduces Chlamydia pneumoniae-induced cell interaction and activation.
BACKGROUND: Chlamydia pneumoniae stimulates chronic inflammation in vascular cells. Hydroxymethylglutaryl coenzyme A reductase inhibitors (statins) may have an ameliorating effect. We investigated possible mechanisms. METHODS AND RESULTS: We infected human macrophages that in coculture spread infection to vascular smooth muscle cells (VSMCs). Cerivastatin (250 nmol/L) reduced VSMC infection by 33%. Western blotting made it apparent that VSMC infection resulted in increased cell membrane-associated RhoA and Rac1, implying increased prenylation of these proteins. This effect was blocked by statin but circumvented by mevalonate. Cytochrome C assays showed that infected VSMCs produced increased reactive oxygen species that was blocked by statin. Infection increased nuclear transcription factor-kappaB expression in VSMCs that was dose-dependently suppressed by statin. Infected VSMCs produced and released RANTES and MCP-1. Statin dose-dependently blocked this production both at the mRNA and protein levels. Mevalonate and M geranylgeranylpyrophosphate circumvented these effects. CONCLUSIONS: C pneumoniae can be transmitted from macrophages to VSMCs. VSMCs showed an activation profile typical of atherosclerosis, namely Rac1 and RhoA prenylation, nuclear transcription factor-kappaB activation, reactive oxygen species production, and chemokine production. Statin reduces macrophage-mediated C pneumoniae-induced signaling and transmission.
The renal arterial resistance index and renal allograft survival.
BACKGROUND: Most renal transplants fail because of chronic allograft nephropathy or because the recipient dies, but no reliable factor predicting long-term outcome has been identified. We tested whether a renal arterial resistance index of less than 80 was predictive of long-term allograft survival. METHODS: The renal segmental arterial resistance index (the percentage reduction of the end-diastolic flow as compared with the systolic flow) was measured by Doppler ultrasonography in 601 patients at least three months after transplantation between August 1997 and November 1998. All patients were followed for three or more years. The combined end point was a decrease of 50 percent or more in the creatinine clearance rate, allograft failure (indicated by the need for dialysis), or death. RESULTS: A total of 122 patients (20 percent) had a resistance index of 80 or higher. Eighty-four of these patients (69 percent) had a decrease of 50 percent or more in creatinine clearance, as compared with 56 of the 479 patients with a resistance index of less than 80 (12 percent); 57 patients with a higher resistance index (47 percent) required dialysis, as compared with 43 patients with a lower resistance index (9 percent); and 36 patients with a higher resistance index (30 percent) died, as compared with 33 patients with a lower resistance index (7 percent) (P<0.001 for all comparisons). A total of 107 patients with a higher resistance index (88 percent) reached the combined end point, as compared with 83 of those with a lower resistance index (17 percent, P<0.001). The multivariate relative risk of graft loss among patients with a higher resistance index was 9.1 (95 percent confidence interval, 6.6 to 12.7). Proteinuria (protein excretion, 1 g per day or more), symptomatic cytomegalovirus infection, and a creatinine clearance rate of less than 30 ml per minute per 1.73 m2 of body-surface area after transplantation also increased the risk. CONCLUSIONS: A renal arterial resistance index of 80 or higher measured at least three months after transplantation is associated with poor subsequent allograft performance and death.
A common polymorphism in KCNH2 (HERG) hastens cardiac repolarization.
OBJECTIVE: Genetic variants of cardiac ion channels may influence cardiac repolarization. Thereby such variants may modulate the penetrance of primary electrical disorders, contribute to differences in susceptibility to drug-induced QT-prolongation between individuals, or contribute to rhythm disturbances in the context of structural heart disease. Since the current encoded by KCNH2 (HERG; I(Kr)) is a primary determinant of repolarization, we conducted association studies between the respective alleles of the common amino acid-changing polymorphism at codon 897 (2690A>C; K897T) within HERG and rate-corrected QT interval (QTc). METHODS AND RESULTS: Association analysis in Caucasian subjects (n=1030) revealed a significant association of this polymorphism with QTc (P=0.0025) with CC homozygotes having a significantly shorter QTc (388.5+/-2.9 ms) compared to AA homozygotes (398.5+/-0.9) and heterozygotes (AC, 397.2+/-1.2). The latter two genotypes were associated with comparable mean QTc's, suggesting that the 2690C-allele is recessive. After stratification by sex, the polymorphism was more predictive of QTc in females (P=0.0021), a finding that was replicated in a second population sample (n=352) from the same ethnic background (P=0.044). To assess whether this polymorphism could represent a 'functional' polymorphism, we compared the biophysical properties of K897- and T897-HERG channels by whole-cell voltage clamp. Compared to the K897 channel, the T897 channel displayed a shift of -7 mV in voltage dependence of activation and increased rates of current activation and deactivation. CONCLUSION: As confirmed in modeling studies, these changes are expected to shorten action potential duration by an increase in I(Kr). This recapitulates the shorter QTc in females homozygous for the 2690C-allele.
Selective impairment in sympathetic vasomotor control with norepinephrine transporter inhibition.
BACKGROUND: Norepinephrine transporter (NET) inhibition increases the responsiveness to vasoactive medications and attenuates the response to sympathetic stimuli. The phenomenon may be a result of impaired regulation of sympathetic vasomotor tone. METHODS AND RESULTS: We studied the effects of the selective NET blocker reboxetine and placebo on baroreflex control of heart rate (HR) and sympathetic traffic in a randomized, double-blind, crossover manner in healthy subjects. Subjects ingested 8 mg reboxetine or placebo 12 hours and 1 hour before testing. ECGs were measured for HR, brachial and finger blood pressure (BP), and muscle sympathetic nerve activity (MSNA). Sympathetic and parasympathetic baroreflex slopes were determined by use of incremental phenylephrine and nitroprusside infusions. The dose to reach BP changes of 12.5 mm Hg was significantly lower during NET inhibition (0.25 versus 0.64 microg x kg(-1) x min(-1) phenylephrine and 0.40 versus 1.10 microg x kg(-1) x min(-1) nitroprusside, P<0.01). Baroreflex control of HR was similar (16 ms/mm Hg with placebo versus 14 ms/mm Hg with reboxetine) but reset to higher BP values. MSNA and sympathetically mediated low-frequency BP oscillations were profoundly reduced at baseline and failed to increase sufficiently during nitroprusside infusion. Reboxetine attenuated BP and MSNA responses to cold pressor testing. CONCLUSIONS: NET inhibition profoundly and selectively reduces baroreflex control of sympathetic vasomotor tone and attenuates the responsiveness to sympathetic stimuli. The reduction in baroreflex buffering increases the sensitivity to vasoactive medications. Therefore, our findings represent a novel mechanism for drug interactions.
Genome-wide linkage reveals a locus for human essential (primary) hypertension on chromosome 12p.
Essential (primary) hypertension is an important risk factor for cardiovascular morbidity and mortality. Blood pressure is largely heritable; however, the genetic factors contributing to essential hypertension are mostly unknown. We examined a large Chinese kindred (n=387) and selected a subset of 94 individuals for genotyping. An additional 32 Chinese nuclear families with essential hypertension were also recruited. Genome-wide parametric linkage analysis identified a new locus for primary hypertension on chromosome 12p (parametric LOD score 3.44). This locus overlaps with the assigned locus that causes severe autosomal-dominant hypertension and brachydactyly, the only form of monogenic hypertension known to date that resembles primary hypertension. We suggest that this genomic region, spanning 18 annotated genes, will be of great relevance in elucidating new mechanisms for primary hypertension.
Inhibition of NF-kappaB by a TAT-NEMO-binding domain peptide accelerates constitutive apoptosis and abrogates LPS-delayed neutrophil apoptosis.
Delivery of biologically active peptides into human polymorphonuclear neutrophils (PMNs) has implications for studying cellular functions and may be therapeutically relevant. The transcription factor nuclear factor-kappaB (NF-kappaB) regulates the expression of multiple genes controlling inflammation, proliferation, and cell survival. PMNs play a crucial role in first-line defense. Targeting NF-kappaB in these cells may promote apoptosis and therefore facilitate resolution of inflammation. We used an 11-amino acid sequence NEMO-binding domain (NBD) that selectively inhibits the IKKgamma (NEMO)/IKKbeta interaction, preventing NF-kappaB activation. An HIV-TAT sequence served as a highly effective transducing shuttle. We show that lipopolysaccharide (LPS), granulocyte-macrophage colony-stimulating factor (GM-CSF), and dexamethasone (DEX) significantly reduced apoptosis after 20 hours. LPS, but not GM-CSF or DEX, activated NF-kappaB as shown by IkappaBalpha degradation, NF-kappaB DNA binding, and transcriptional activity. The TAT-NBD blocked LPS-induced NF-kappaB activation and NF-kappaB-dependent gene expression. TAT-NBD accelerated constitutive PMN apoptosis dose dependently and abrogated LPS-delayed apoptosis. These results provide a proof of principle for peptide delivery by TAT-derived protein transduction domains to specifically inhibit NF-kappaB activity in PMNs. This strategy may help in controlling various cellular functions even in short-lived, transfection-resistant primary human cells.
Baa, Baa, black sheep, are your kidneys full?
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Pressor effect of water drinking in tetraplegic patients may be a spinal reflex.
Water drinking elicits a profound sympathetically mediated pressor response in patients with autonomic failure. To further elucidate the mechanism of the response, we assessed the acute effect of drinking water on supine blood pressure and heart rate in 13 tetraplegic patients (12 men, 1 woman; 39+/-4 years of age; body mass index, 25+/-1 kg/m2) with complete spinal cord injury (C2 to C7). Heart rate and finger blood pressure were recorded continuously. Brachial blood pressure was measured every 5 minutes. Baroreflex sensitivity was assessed by the sequence method. Stroke volume was calculated by use of transthoracic bioimpedance. Patients were placed in the supine position with the upper body elevated by 15 degrees. After 30 minutes, supine patients ingested 500 mL of water and the following 60 minutes were monitored. Finger blood pressure at baseline was 123+/-8/65+/-4 mm Hg. Water drinking elicited a pressor response that was apparent within 5 minutes and reached a maximum of 138+/-8/73+/-4 mm Hg after 35 to 40 minutes (P<0.05). Heart rate decreased from 64+/-2 bpm at baseline to 60+/-2 bpm (P<0.001). The mean area under the curve for brachial systolic blood pressure changes differed significantly from zero (364+/-151 mm Hg/min). Total peripheral resistance increased by 15+/-4% (P<0.05). Baroreflex sensitivity increased from 18+/-5 ms/mm Hg at baseline to 23+/-6 ms/mm Hg at 35 minutes after water drinking (P<0.01). Water drinking elicits a pressor response even if the direct connection between brain stem cardiovascular centers and spinal sympathetic neurons is interrupted. This observation might suggest that water drinking activates postganglionic sympathetic neurons either directly or through a spinal reflex mechanism.
Exercising restraint in measuring blood pressure in conscious mice.
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AT1 receptor agonistic antibodies from preeclamptic patients stimulate NADPH oxidase.
BACKGROUND: We recently identified agonistic autoantibodies directed against the angiotensin AT1 receptor (AT1-AA) in the plasma of preeclamptic women. To elucidate their role further, we studied the effects of AT1-AA on reactive oxygen species (ROS), NADPH oxidase expression, and nuclear factor-kappaB (NF-kappaB) activation. METHODS AND RESULTS: We investigated human vascular smooth muscle cells (VSMC) and trophoblasts, as well as placentas. AT1-AA were isolated from sera of preeclamptic women. Angiotensin II (Ang II) and AT1-AA increased ROS production and the NADPH oxidase components, p22, p47, and p67 phox in Western blotting. We next tested if AT1-AA lead to NF-kappaB activation in VSMC and trophoblasts. AT1-AA activated NF-kappaB. Inhibitor-kappaBalpha (I-kappaBalpha) expression was reduced in response to AT1-AA. AT1 receptor blockade with losartan, diphenylene iodonium, tiron, and antisense against p22 phox all reduced ROS production and NF-kappaB activation. VSMC from p47phox-/- mice showed markedly reduced ROS generation and NF-kappaB activation in response to Ang II and AT1-AA. The p22, p47, and p67 phox expression in placentas from preeclamptic patients was increased, compared with normal placentas. Furthermore, NF-kappaB was activated and I-kappaBalpha reduced in placentas from preeclamptic women. CONCLUSIONS: NADPH oxidase is potentially an important source of ROS that may upregulate NF-kappaB in preeclampsia. We suggest that AT1-AA through activation of NADPH oxidase could contribute to ROS production and inflammatory responses in preeclampsia.
Haplotypes, "hyplotypes," and complex genetic disease.
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