Nanoparticle delivery of grape seed-derived proanthocyanidins to airway epithelial cells dampens oxidative stress and inflammation.

BACKGROUND: Chronic respiratory diseases, whose one of the hallmarks is oxidative stress, are still incurable and need novel therapeutic tools and pharmaceutical agents. The phenolic compounds contained in grape are endowed with well-recognized anti-oxidant, anti-inflammatory, anti-cancer, and anti-aging activities. Considering that natural anti-oxidants, such as proanthocyanidins, have poor water solubility and oral bioavailability, we have developed a drug delivery system based on solid lipid nanoparticles (SLN), apt to encapsulate grape seed extract (GSE), containing proanthocyanidins. METHODS: Plain, 6-coumarin (6-Coum), DiR- and GSE-loaded SLN were produced with the melt-emulsion method. Physicochemical characterization of all prepared SLN was determined by photon correlation spectroscopy and laser Doppler anemometry. MTT assay (spectrophotometry) and propidium iodide (PI) assay (cytofluorimetry) were used to assess cell viability. Flow cytometry coupled with cell imaging was performed for assessing apoptosis and necrosis by Annexin V/7-AAD staining (plain SLE), cell internalization (6-Coum-SLN) and reactive oxygen species (ROS) production (SLN-GSE). NF-κB nuclear translocation was studied by immunofluorescence. In vivo bio-imaging was used to assess lung deposition and persistence of aerosolized DiR-loaded SLN. RESULTS: Plain SLN were not cytotoxic when incubated with H441 airway epithelial cells, as judged by both PI and MTT assays as well as by apoptosis/necrosis evaluation. 6-Coum-loaded SLN were taken up by H441 cells in a dose-dependent fashion and persisted into cells at detectable levels up to 16 days. SLN were detected in mice lungs up to 6 days. SLN-GSE possessed 243 nm as mean diameter, were negatively charged, and stable in size at 37 °C in Simulated Lung Fluid up to 48 h and at 4 °C in double distilled water up to 2 months. The content of SLN in proanthocyanidins remained unvaried up to 2 months. GSE-loaded SLN determined a significant reduction in ROS production when added 24-72 h before the stimulation with hydrogen peroxide. Interestingly, while at 24 h free GSE determined a higher decrease of ROS production than SLN-GSE, the contrary was seen at 48 and 72 h. Similar results were observed for NF-κB nuclear translocation. CONCLUSIONS: SLN are a biocompatible drug delivery system for natural anti-oxidants obtained from grape seed in a model of oxidative stress in airway epithelial cells. They feature stability and long-term persistence inside cells where they release proanthocyanidins. These results could pave the way to novel anti-oxidant and anti-inflammatory therapies for chronic respiratory diseases.

Adipose-derived mesenchymal stromal (stem) cells differentiate to osteoblast and chondroblast lineages upon incubation with conditioned media from dental pulp stem cell-derived osteoblasts and auricle cartilage chondrocytes.

The potential of adipose-derived mesenchymal stromal (stem) cells (ADSCs) to differentiate into either osteoblasts or chondrocytes is controversial. In this study we investigated the multicapacity potential of ADSCs to differentiate towards adipocyte, osteoblast, and chondrocyte lineages when cells are seeded onto plastic in comparison with incubation with conditioned media (CM) obtained from differentiated cell types.ADSCs, obtained from liposuctions, were characterized for mesenchymal and hematopoietic markers by cytofluorimetry. Their differentiation capacity towards adipocytes, osteoblasts, and chondrocytes was investigated by histochemistry methods (Oil-Red-O staining, Safranin O and Alizarin Red staining, respectively). Dental pulp stem cells (DPSCs) and dedifferentiated auricle derived-chondrocytes were differentiated towards osteoblastic and chondrocytic lineages respectively, and the CM obtained from these cultures was used to induce differentiation of ADSCs. ADSCs were positive for mesenchymal markers (CD29, CD105, CD73, CD44), but not for hematopoietic lineage markers (CD14, CD34, CD45) and this behavior was conserved from the isolation up to the fifth passage. While ADSCs were readily differentiated in adipocytes, they were not towards chondrocytes and osteoblastic lineages, a behavior different from that of bone marrow-derived MSCs that differentiated into the three lineages at two weeks post-induction. Only ADSCs treated with CM from cultured chondrocytes and DPSCs, produced glycosaminoglycans and mineralized matrix. These results indicate that ADSCs need growth/morphogenic factor supplementation from the tissue environment to be appropriately differentiated to mesodermic lineages.

Adhesion and growth of osteoblast-like cells on laser-engineered porous titanium surface: expression and localization of N-cadherin and beta-catenin.

Response of different types of cells on biomaterials is crucial for the applications of tissue engineering and regenerative medicine. It is recognized that cell behaviour depends largely on material surface characteristics. The purpose of this study was to define the biologic response of MG63 cells to the innovative patented surface SYNTHEGRA. MG63 morphology and distribution on the three different titanium disk surfaces (sandblasted, smooth, and laser-treated) were evaluated by microscopy analysis after staining with hematoxylin and eosin. Cell adhesion was determined by crystal violet assay at 48 h while proliferation and cytotoxicity were performed by MTT assay at 24, 48, 72 and 240 h. The expression and localization of N-cadherin and beta-catenin were studied by immunofluorescence and confocal microscopy. At 48 h the adhesion was similar in all titanium surfaces, no difference in cell viability were observed in all titanium disks when compared with controls, while the cell growth on laser-treated disks was significantly higher at 240 h than at 24 and 72 h. Morphological analysis show that cells are aligned along the grooves and inside the cavities. beta-catenin signal appeared more diffuse and localized underneath the cell membrane, while N-cadherin signal was fainter in cells grown on SYNTHEGRA surface. This work put into evidence the performance of newly designed laser-micromachined surface for adhesion, growth and distribution of human osteoblast-like cells. SYNTHEGRA surface inducing modification of N-cadherin and beta-catenin expression and localization, are suggestive of cells undergoing differentiation towards osteocytes and could be particularly suited for immediate load implant procedures.

CFTR expression and activity from the human CFTR locus in BAC vectors, with regulatory regions, isolated by a single-step procedure.

We have assembled two BAC vectors containing a single fragment spanning the entire CFTR locus and including the upstream and downstream regions. The two vectors differ in size of the upstream region, and were recovered in Escherichia coli, with intact BAC DNAs prepared for structural and functional analyses. Sequence analysis allowed precise mapping of the inserts. We show that the CFTR gene was wild type and is categorized as the most frequent haplotype in Caucasian populations, identified by the following polymorphisms: (GATT)7 in intron 6a; (TG)11T7 in intron 8; V470 at position 470. CFTR expression and activity were analyzed in model cells by RT-PCR, quantitative real-time PCR, western blotting, indirect immunofluorescence and electrophysiological methods, which show the presence of an active CFTR Cl ⁻ channel. Finally, and supporting the hypothesis that CFTR functions as a receptor for Pseudomonas aeruginosa, we show that CFTR-expressing cells internalized more bacteria than parental cells that do not express CFTR. Overall, these data demonstrate that the BAC vectors contain a functional CFTR fragment and have unique features, including derivation from a single fragment, availability of a detailed genomic map and the possibility to use standard extraction procedures for BAC DNA preparations.

Color Doppler ultrasonography of the abdominal aorta.

Alterations of the abdominal aorta are relatively common, particularly in older people. Technological advances in the fields of ultrasonography, computed tomography, angiography, and magnetic resonance imaging have greatly increased the imaging options for the assessment of these lesions. Because it can be done rapidly and is also non-invasive, ultrasonography plays a major role in the exploration of the abdominal aorta, from its emergence from the diaphragm to its bifurcation. It is indicated for the diagnosis and follow-up of various aortic diseases, especially aneurysms. It can be used to define the shape, size, and location of these lesions, the absence or presence of thrombi and their characteristics. It is also useful for monitoring the evolution of the lesion and for postoperative follow-up. However, its value is limited in surgical planning and in emergency situations.

Sublingual immunotherapy: from safety to mechanism of action.

Allergen specific immunotherapy is an important option for the treatment of respiratory allergy and its clinical efficacy has been clearly demonstrated by several studies. However, the injective route of administration and the possibility of severe side effects has limited its use in children and led to the introduction of new forms of administration. Sublingual immunotherapy (SLIT) has proven to be an effective and safe treatment for respiratory allergy. However, its mechanism of action is still debated. Pharmacokinetic studies showed that, differently from nasal mucosa, allergen extracts administered by SLIT are not immediately adsorbed but are long retained before being drained to local lymph nodes. This difference may be responsible of the absence of severe side effects and instead of short-lasting local symptoms. Studies by biopsies of the oral mucosa should greatly help in defining the presence and the role of cells involved in the mechanisms of oral tolerance.

Angiotensin-converting enzyme I/D polymorphism and macrovascular disease in systemic sclerosis.

OBJECTIVE: Systemic sclerosis (SSc) is characterized by microvascular and macrovascular alterations. The D allele of the ACE I/D polymorphism is known to be associated with an increased incidence of atherosclerosis and has been recently proposed as associated with increased risk of SSc. This study evaluates the relationship between intima-media thickness (IMT), ankle-brachial pressure measurements (ABPI) and ACE I/D polymorphism in SSc patients. METHODS: According to the presence of ACE D allele (analysed by PCR), 53 SSc patients (47 females and 6 males; median age was 60.4 +/- 10.68 yrs; range 40-75 yrs) were divided in carriers of the D allele (DD + ID) (n = 46) and carriers of the I allele (II) (n = 7). In these patients, IMT and ABPI [calculated as the posterior tibial artery pressure (mmHg) divided by the brachial pressure] were obtained. Forty-three healthy controls (40 women and 13 men; median age 56.3 +/- 10.23; range 40-70 yrs) of the same ethnicity were recruited. RESULTS: SSc patients had IMT significantly higher than controls (0.85 +/- 0.03 vs 0. 68 +/- 0.01; P < 0.03). No significant differences (P > 0.3) in ABPI values between patients (1.018 +/- 0.10) and controls (1.091 +/- 0.11) were found. SSc patients with ACE DD and ID genotype showed an IMT significantly greater (0.89 +/- 0.03) than those carrying the II genotype (0.61 +/- 0.01) (P < 0.04). ABPI was not different among ACE gene genotypes. CONCLUSION: Our findings confirm an increased prevalence of macrovascular disease in SSc patients and show that IMT is greater in patients carrying the ACE DD and ID genotype in comparison with II homozygotes. This suggests that, in SSc, the presence of ACE D allele may predispose to an involvement of the macrovascular system.

Circulating levels of Nepsilon-(carboxymethyl)lysine are increased in systemic sclerosis.

OBJECTIVE: Advanced glycation endproducts (AGEs), including Nepsilon-(carboxymethyl)lysine-protein adducts (CML) are involved in micro/macrovascular changes and are co-localized with adhesion molecules in inflamed tissues. Serum levels of CML were investigated in systemic sclerosis (SSc) characterized by microvascular modifications and correlated with indices of micro/macrovascular damage. METHODS: In 66 SSc patients (limited SSc, n = 55; diffuse SSc, n = 11) and 20 controls, CML serum levels were measured by enzyme-linked immunosorbent assay. Nailfold capillaroscopy, intima-media thickness (IMT) and the ankle-brachial index (ABI) were also recorded, to characterize micro/macrovascular involvement. RESULTS: CML levels were significantly higher in SSc (79.2 +/- 39 mg/ml vs 49.6 +/- 26.1 mg/ml, mean +/- s.d.; P<0.01), without significant differences between SSc subsets. CML levels were significantly higher in all capillaroscopic patterns: the 'early' pattern showed higher levels than 'active' and 'late' patterns. IMT was significantly higher in SSc (P<0.01) than in controls, whilst ABI was no different from controls. CONCLUSIONS: These data indicate that although both CML formation and macrovascular involvement are increased in SSc, there is no correlation between these two parameters. However, the characteristic early nailfold capillaroscopy changes of SSc are associated with proportionally greater CML formation, suggesting that AGEs are involved in SSc microangiopathy.

Cognitive impairment and carotid atherosclerosis in a general Italian midlife and old population.

The authors describe the design and the general, ultrasonographic, neuropsychological methodology of an observational epidemiological population survey, named REMEMBER (Registry Evaluation Memory in Buttrio e Remanzacco) conducted in the northeast of Italy in a randomized stratified sample of 1,026 subjects (554 F and 472 M) aged 55-98 years. The study was planned as cross-sectional and longitudinal survey of cognitive impairment, cardiovascular risk factors, carotid atherosclerosis in a midlife and older Italian population sample. The objectives of the first phase are to assess the prevalence of the different types of dementia, the cognitive impairment non-dementia, the cardiovascular risk factors, the carotid intima-media thickness and arterial distensibility, and of depression. The conclusions of this study will make it possible to organize preventive and interventional strategies for these epidemic conditions.

Homocysteine-lowering therapy and carotid intima-media thickness in renal transplant recipients.

The aim of this study was to document, in hyperhomocysteinemic renal transplant recipients, the effect of vitamin supplementation on carotid intima-media thickness (cIMT). Fifty-six hyperhomocysteinemic stable renal transplant recipients were randomly assigned to either vitamin supplementation (group A) or placebo treatment (group B). All patients underwent high-resolution B mode ultrasound to measure IMT of common carotid arteries before and after 6 months of vitamin supplementation. In group A, cIMT significantly decreased after treatment, whereas no significant changes were observed in group B. In conclusion, our results demonstrate a beneficial effect of the treatment of hyperhomocysteinemia by vitamin supplementation on an early sign of atherosclerosis in a group of renal transplant recipients.

Renal adaptive mechanisms in aged and hypertensive humans: possible effects of treatment.

BACKGROUND: In the aging kidney renal blood flow and glomerular filtration rate are reduced due to glomerulosclerosis. On this regard, hypertension has synergistic effects and may lead to end-stage renal disease in a significant proportion of cases. MATERIAL AND METHODS: To study the effects of antihypertensive drugs in an acute setting, we expressly designed an acute experiment to assess the renal response to mental stress (MS). In healthy elderly, the response was characterized by a prolonged and pronounced renal vasoconstriction, due to a reduction in renal autacoid modulatory capacity, particularly of prostaglandins. In older patients with isolated systolic hypertension, the response to MS was impaired, being characterized by a passive vasodilation with hyperfiltration. The effects of antihypertensive drugs were evaluated twice in adults patients with mild to moderate essential hypertension: after two weeks of pharmacological wash-out and after two weeks of treatment with the ACE-inhibitor trandolapril (4 mg), or the non-dihydropyridinic Ca2+ channel blocker verapamil (240 mg), or both (2 mg + 180 mg). RESULTS: While the three antihypertensive regimens reduced blood pressure to a similar extent, their effects on the renal response to MS were different. Each regimen re-established a renal vasoconstrictive response to adrenergic activation. However, with trandolapril, renal vasoconstriction was limited, as it occurs physiologically, to the period of blood pressure rise, while verapamil, or the combination of the two drugs, were associated with more prolonged vasoconstriction. CONCLUSIONS: Further studies are needed to confirm the nephroprotective effects of these drugs, particularly of ACE-inhibitors. These data may be a pathophysiological basis for future clinical trials.

Double reinforcement with fludarabine/high-dose cytarabine enhances the impact of autologous stem cell transplantation in acute myeloid leukemia patients.

Reinforced chemotherapy based on a double high-dose consolidation regimen could be a different way to enhance in vivo purging prior to autologous stem cell transplantation (auto-SCT) in acute myeloid leukemia (AML). We investigated the impact on outcome of auto-SCT after two different strategies of early intensification performed after an identical induction regimen in adult patients with AML. Between January 1993 and December 1998, 140 consecutive AML patients were enrolled in a program consisting of an identical anthracycline-based induction (ICE) and two different consolidation regimens: one cycle, cytarabine-based (single-NOVIA: 91 patients); two cycles, fludarabine-based (double-FLAN: 49 patients). Seventy out of 91 patients received single-NOVIA consolidation: 60 underwent a transplantation procedure (allogeneic bone marrow transplantation (allo-BMT):16 patients; auto-SCT: 44). Thirty-five out of 49 patients received double-FLAN consolidation: 31 underwent a transplantation procedure (allo-BMT: 10; auto-SCT: 21). The double consolidation regimen was well-tolerated with only minor side-effects. Median follow-up observation time for surviving patients was 38 months (range, 17-71) for the double-FLAN consolidation group and 70 months (range: 48-93) for the single-NOVIA consolidation group. Among the patients who received auto-SCT, the double consolidation strategy produced a superior disease-free survival curve at 36 months (78.6% (95%CI: 59.4-97.8) vs 47.7% (95%CI: 33-62.4)) compared with the single-NOVIA group. This difference was confirmed when the patients were analyzed for intention to treat (P = 0.04). In addition, the double-FLAN consolidation group showed a superior overall survival and lower relapse rate (P = 0.02). We conclude that the double-FLAN reinforcement strategy is safe and enhances the clinical impact of auto-SCT for AML patients in first complete remission. It may provide specific clinical benefit for patients undergoing auto-SCT.

Mutation of residues in the coenzyme binding pocket of Dopa decarboxylase. Effects on catalytic properties.

Residues D271, H192, H302 and N300 of L-3,4-dihydroxyphenylalanine decarboxylase (DDC), a homodimeric pyridoxal 5'-phosphate (PLP) enzyme, were mutated in order to acquire information on the catalytic mechanism. These residues are potential participants in catalysis because they belong to the common PLP-binding structural motif of group I, II and III decarboxylases and other PLP enzymes, and because they are among the putative active-site residues of structural modelled rat liver DDC. The spectroscopic features of the D271E, H192Q, H302Q and N300A mutants as well as their dissociation constants for PLP suggest that substitution of each of these residues causes alteration of the state of the bound coenzyme molecule and of the conformation of aromatic amino acids, possibly in the vicinity of the active site. This supports, but does not prove, the possibility that these residues are located in the coenzyme-binding cleft. Interestingly, mutation of each residue generates an oxidative decarboxylase activity towards L-3,4-dihydroxyphenylalanine (L-Dopa), not inherent in the wild-type in aerobiosis, and reduces the nonoxidative decarboxylase activity of L-Dopa from 3- to 390-fold. The partition ratio between oxidative and nonoxidative decarboxylation ranges from 5.7 x 10(-4) for N300A mutant to 946 x 10(-4) for H302Q mutant. Unlike wild-type enzyme, the mutants catalyse these two reactions to the same extent either in the presence or absence of O2. In addition, all four mutants exhibit an extremely low level of the oxidative deaminase activity towards serotonin with respect to wild-type. All these findings demonstrate that although D271, H192, H302 and N300 are not essential for catalysis, mutation of these residues alters the nature of catalysis. A possible relationship among the integrity of the PLP cleft, the productive binding of O2 and the transition to a closed conformational state of DDC is discussed.

Changes in renal autacoids and hemodynamics associated with aging and isolated systolic hypertension.

The aging kidney is characterized by a decrease in renal blood flow and glomerular filtration rate mainly due to glomerulosclerosis. Nevertheless, even in the presence of these changes, the kidney maintains its functionality until advanced age. However, there is a tendency towards greater renal vasoconstriction in the elderly as compared with young individuals. This occurs either in physiological circumstances such as physical exercise, or in disease manifestations, such as the effective circulatory volume depletion that develops, for example, in heart failure. This tendency may be secondary to the reduction of renal autacoid modulatory capacity, particularly at the vasodilating prostaglandin level. In an acute experimental model we could demonstrate that, in the healthy elderly, the renal response to adrenergic activation by mental stress is characterized by a prolonged and pronounced vasoconstriction. In addition to this, in elderly patients affected by isolated systolic hypertension, we demonstrated an impairment of renal hemodynamic and humoral adaptation capacity in response to adrenergic activation and blood pressure increase. In the presence of sudden blood pressure increase, the kidney of these patients responds with a passive vasodilation and a glomerular filtration rate increase without any activation of humoral modulatory substances. The impairment in renal adaptation capacity may predispose these patients to renal injury, particularly in the presence of the many hypertensive peaks which characterize everyday life of elderly individuals. In conclusion, these results show that renal adaptation capacity of elderly patients with isolated systolic hypertension is completely lost. Further studies will elucidate whether antihypertensive treatment per se, or specific classes of antihypertensive drugs, are able to revert this impairment.

Changes in renal autacoids in aged human hypertensives.

The aging process determines several modifications of the kidney, that, however, do not provoke any dysfunction in normal conditions. But in the elderly--in the presence of stressful situations and particularly when adrenergic activation is present--the kidney is more vulnerable than in the young, and renal failure may arise. Variations typical of the aging kidney are accelerated when hypertension overlaps the physiological renal process, because both senescence and hypertension weight on the same structures, i.e. glomeruli. We studied renal hemodynamic adaptation capacity both in the healthy elderly and in patients affected by isolated systolic hypertension, in an acute experiment which requires the application of a mental stress-induced adrenergic activation. In hypertensive patients we have already demonstrated a total lack of renal adaptation capacity. In fact, while the elderly normotensives react with a prolonged and pronounced vasoconstriction, in those with isolated systolic hypertension, adrenergic activation induces a passive renal vasodilation and glomerular hyperfiltration. The anomalous adaptation capacity of renal hemodynamics is probably due to an impairment in the paracrine response of renal vasculature. Indeed in the hypertensive elderly, unlike in the normotensive one, no variations of autacoid production occur during the adrenergic activation. Following on from this, pattients affected by isolated systolic hypertension passively suffer the many hypertensive peaks which characterize their every day life. The altered renal autoregulation of the elderly with isolated systolic hypertension may explain the accelerated glomerulosclerosis and the greater incidence of renal damage and end-stage renal disease which characterize this condition. These aspects underline the primary role of the antihypertensive treatment of isolated systolic hypertension, not only for the prevention of cardiovascular mortality but also of renal damage and/or end-stage renal disease.

Impaired renal adaptation to stress in the elderly with isolated systolic hypertension.

The aim of this study was to evaluate the renal response in the elderly with isolated systolic hypertension (ISH) when an adrenergic activation, as induced by mental stress, is applied. Renal hemodynamics and kidney neurohumoral response to mental stress were studied in 8 elderly patients with ISH (aged 63 to 82 years) along with 8 elderly normotensive subjects. The study encompassed four 30-minute experimental periods (baseline, mental stress, and recovery I and II). In these patients, the mental stress-induced blood pressure rise was associated with a significant increase in both effective renal plasma flow ((131)I-labeled hippurate clearance) and glomerular filtration rate ((125)I-labeled iothalamate clearance) (+42% and +29%, respectively; P<0.01 for both), without variations in filtration fraction, while elderly normotensives reacted to adrenergic stimulation with renal vasoconstriction but with the glomerular filtration rate constant. Variations in renal vasoactive substances, which paralleled hemodynamics of the kidney, differed in the 2 groups. In normotensives, excretion (radioimmunoassay) of endothelin-1, prostaglandin E(2), and cGMP increased during the stimulus (+50%, +54%, and +59%, respectively; P<0.05). In ISH patients the release of these autacoids did not vary in any of the experimental periods. In conclusion, in patients with ISH the renal adaptive capacity to sympathetic activation is impaired, and the data may suggest that the glomerulus passively suffers the blood pressure increase, probably because of the insufficiency of the neurohumoral response, particularly in regard to the increase of endothelin-1. This hemodynamic pattern may predispose ISH patients to a higher risk of renal injury.

Characterization of autotransplant-related thrombocytopenia by evaluation of glycocalicin and reticulated platelets.

Thrombocytopoiesis of 21 multiple myeloma patients undergoing single or double transplant regimen was characterized by measuring the level of reticulated platelets and plasma glycocalicin. Since reticulated platelets are an index of thrombopoietic activity and glycocalicin plasma values are related to platelet damage and turnover, it may be possible to perform a novel type of analysis of the thrombopoietic compartment during the mobilizing regimen and during transplant-related chemotherapy. Patients underwent mobilizing therapy and first transplant. Some randomized patients also underwent a second transplant with mobilized peripheral blood stem cells. The results show that the percentage of reticulated platelets decreased after therapy and then gradually increased in the recovery phase either during first or second transplant. By contrast, the percentage of reticulated platelets increased until day +8 and then gradually decreased during the mobilizing regimen. The glycocalicin index (glycocalicin plasma value normalized for the individual platelet count) increased significantly both during the course of mobilization and after transplant-related chemotherapy when the platelet number was at its nadir. However, the glycocalicin index was more elevated after transplant-related chemotherapy than after the mobilizing regimen. Our findings suggest that chemotherapy-related thrombocytopenia may be due to a dual mechanism: thrombocytopenia results from decreased platelet production in addition to increased platelet damage and possible destruction.

Excessive vasoconstriction after stress by the aging kidney: inadequate prostaglandin modulation of increased endothelin activity.

The adaptive capacity of the aging kidney to stimulation of the sympathetic nervous system, as induced by a 30-minute mental stress (MS), was assessed in 8 elderly healthy women (68 to 82 years of age) and compared with that of 8 younger women (24 to 40 years of age). The study encompassed 4 consecutive 30-minute periods (baseline, mental stress, recovery 1, and recovery 2). In the elderly subjects, baseline effective renal plasma flow (ERPF)(iodine 131-labeled hippurate clearance) was lower and glomerular filtration rate (GFR)(iodine 125-labeled iothalamate clearance) was proportionally less reduced than in the younger group; the filtration fraction (FF) was higher. The elderly group excreted more endothelin 1 (ET-1) (P < .05), prostaglandin E2 (PGE2), and 6-keto-prostaglandin F1alpha (6-keto PGF1alpha)(P < .001 for both)(radioimmunoassay). Mental stress induced similar increases in blood pressure, heart rate, and plasma catecholamines in the 2 age groups, limited to the stimulation period. In the elderly group, mental stress caused a prolonged decrease in ERPF that reached its maximum 60 minutes after mental stress (-33%, P < .05), while GFR remained constant during the whole experiment, so that FF increased. In the younger subjects, renal hemodynamic changes were limited to the mental stress period. ET-1 increased during mental stress and the first recovery period in the elderly group (+50% and +25%, P < .05) as it did in the younger group, but the elderly group differed from the younger in that vasodilating prostaglandins increased only during mental stress. In conclusion, the aging kidney reacts to adrenergic stimulation with more-pronounced and -prolonged vasoconstriction that is probably caused by a defect in prostaglandin modulation of endothelin activity. Autoregulation of GFR is maintained at the expense of increased intraglomerular pressure.

Mutation of cysteine 111 in Dopa decarboxylase leads to active site perturbation.

Cysteine 111 in Dopa decarboxylase (DDC) has been replaced by alanine or serine by site-directed mutagenesis. Compared to the wild-type enzyme, the resultant C111A and C111S mutant enzymes exhibit Kcat values of about 50% and 15%, respectively, at pH 6.8, while the K(m) values remain relatively unaltered for L-3,4-dihydroxyphenylalanine (L-Dopa) and L-5-hydroxytryptophan (L-5-HTP). While a significant decrease of the 280 nm optically active band present in the wild type is observed in mutant DDCs, their visible co-enzyme absorption and CD spectra are similar to those of the wild type. With respect to the wild type, the Cys-111-->Ala mutant displays a reduced affinity for pyridoxal 5'-phosphate (PLP), slower kinetics of reconstitution to holoenzyme, a decreased ability to anchor the external aldimine formed between D-Dopa and the bound co-enzyme, and a decreased efficiency of energy transfer between tryptophan residue(s) and reduced PLP. Values of pKa and pKb for the groups involved in catalysis were determined for the wild-type and the C111A mutant enzymes. The mutant showed a decrease in both pK values by about 1 pH unit, resulting in a shift of the pH of the maximum velocity from 7.2 (wild-type) to 6.2 (mutant). This change in maximum velocity is mirrored by a similar shift in the spectrophotometrically determined pK value of the 420-->390 nm transition of the external aldimine. These results demonstrate that the sulfhydryl group of Cys-111 is catalytically nonessential and provide strong support for previous suggestion that this residue is located at or near the PLP binding site (Dominici P, Maras B, Mei G, Borri Voltattorni C. 1991. Eur J Biochem 201:393-397). Moreover, our findings provide evidence that Cys-111 has a structural role in PLP binding and suggest that this residue is required for maintenance of proper active-site conformation.