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Biomedical subjects

A Leonardi

Publications and source records attributed to A Leonardi.

At least 55 records · Page 3Linked to original sources
PubMed1999

Histamine effects on conjunctival fibroblasts from patients with vernal conjunctivitis.

Histamine, an important mast cell mediator in allergic disorders, may affect extracellular matrix production and cell growth in vernal keratoconjunctivitis (VKC). In the present study, the histamine reactivity of conjunctival fibroblasts derived from VKC patients was investigated in vitro. Conjunctival fibroblast cultures were derived from biopses of 8 tarsal VKC patients and 5 normal subjects. These cells were maintained in vitro and stimulated with different concentrations of histamine with and without H1 (clorpheniramine) and H2 (cimetidine) receptor antagonists. Comparisons were made to fibroblasts grown in the same media without histamine and to fibroblasts stimulated with just antihistamine. The effects of histamine were evaluated by: (1) the MTT test to assess cell proliferation; (2) an in vitro wound model for cell migration and (3) the measurement of procollagen I (PIP) and procollagen III (PIIIP) in supernatants for collagen production. Results showed: (1) While VKC-derived fibroblasts proliferated at a faster rate than normal cells in unstimulated media, after histamine stimulation, VKC and normal cells grew at a similar rate. Both H1 and H2 antagonists significantly inhibited (P<0.05) histamine-induced cell proliferation. (2) Histamine enhanced cell migration after wounding; this effect was inhibited only by H2 antagonism. (3) When stimulated with histamine, VKC fibroblasts produced significantly more PIP than those in control media. Furthermore, VKC-derived fibroblasts were more sensitive to histamine challenge, producing significantly more PIP than normal fibroblasts. H1 and H2 antagonists did not modify histamine-stimulated PIP production. The enhanced proliferative and productive capacity of VKC fibroblasts may be the result of a selective overgrowth of one or more fibroblast subpopulations in a chronically inflamed tissue. Histamine increased proliferation, migration and collagen production in both normal and VKC fibroblasts. Since H2 antagonism modulated both cell growth and migration, but not histamine-induced collagen production, the latter may be mediated by a different receptor. These results showed that histamine is at least partially responsible for fibroblast stimulation.

Cell Culture Techniques↗
PubMed1999

Ivr2, a candidate gene for a QTL of vacuolar invertase activity in maize leaves. Gene-specific expression under water stress.

Water shortage produced an early and large stimulation of acid-soluble invertase activity in adult maize leaves whereas cell wall invertase activity remained constant. This response was closely related to the mRNA level for only one of the invertase gene (Ivr2), encoding a vacuolar isoform. In parallel, four quantitative trait loci (QTLs) were detected for invertase activity under control and nine under stressful conditions. One QTL in control and one in stressed plants was located near to the Ivr2 gene on chromosome 5. Other QTLs for invertase activity were found close to carbohydrate QTLs; some of them formed 'stress clusters'.

DNA, Plant↗
PubMed1999

Cytokine production and mRNA expression by conjunctival T-cell lines in chronic allergic eye disease.

BACKGROUND: Activated CD4+ T cells, mast cells and eosinophils are the main cytokine-producing cell-types infiltrating the conjunctiva during chronic allergic eye diseases. Interactions between these cells are thought to play an important immunopathogenic role in these disorders (giant papillary conjunctivitis; vernal keratoconjunctivitis; atopic keratoconjunctivitis). OBJECTIVE: The objective was to compare the cytokine profiles of conjunctival T-cell lines from patients with different forms of chronic allergic eye disease. METHODS: T cells were isolated from conjunctival biopsies and non-specifically expanded into lines. The lines were immunophenotyped by flow cytometry. Cytokine production was quantified by immunoassays and more sensitive molecular techniques were used to investigate cytokine mRNA expression to identify the presence of interleukin (IL) -2, IL-4 and interferon (IFN) -gamma transcripts. RESULTS: Following four to six rounds of stimulation, the conjunctival T-cell populations were CD3+ (> 93%), with variable levels of CD4 and CD8 expression. All were HLA-DR+ (> 80%) with some HLA-DQ expression. Conjunctival T-cell lines from atopic keratoconjunctivitis produced selective increases in IFN-gamma, IL-10 and IL-13 (P<0.01), those from vernal keratoconjunctivitis produced increased IL-5 (P<0.01) whereas T-cell lines from giant papillary conjunctivitis produced only low levels of cytokines. IL-4 was only detected at the mRNA level and was expressed in four out of five T-cell lines in the vernal keratoconjunctivitis group. In contrast there was moderate to strong expression of IFN-gamma in five out of six T-cell lines in atopic keratoconjunctivitis. CONCLUSION: Different patterns of T-cell cytokine profiles were observed for each disease, with low-level, non-polarized cytokine production in giant papillary conjunctivitis, a TH2-like profile in vernal keratoconjunctivitis and a shift towards a TH1-like profile in atopic keratoconjunctivitis.

Adult↗
PubMed1999

Granulocyte-macrophage colony-stimulating factor activity in cerebrospinal fluid.

OBJECTIVES: The purpose of this study was to analyse the presence of the granulocyte-macrophage colony-stimulating factor (GM-CSF) in human cerebrospinal fluid (SF) of patients affected by multiple sclerosis (MS) in comparison with non-inflammatory neurological diseases. MATERIAL AND METHODS: All SFs were collected from 59 patients for diagnostic purpose. The presence of GM-CSF was revealed by measuring its activity and by immunoassay. The data obtained were statistically evaluated. RESULTS: We found that GM-CSF is constitutively present in human SF; this presence was confirmed by its stimulating activity of colony-forming-unit granulocyte-macrophage (CFU-GM) production. No significant changes of the GM-CSF concentration in the SFs were observed among different neurological disorders (degenerative or vascular) and MS. CONCLUSION: Our data suggest that GM-CSF is a constitutive component of human SF, relatively uninfluenced by the different morbid conditions of the nervous system.

Blotting, Western↗
PubMed1999

Inverse agonism and neutral antagonism at alpha(1a)- and alpha(1b)-adrenergic receptor subtypes.

We have characterized the pharmacological antagonism, i.e., neutral antagonism or inverse agonism, displayed by a number of alpha-blockers at two alpha1-adrenergic receptor (AR) subtypes, alpha(1a)- and alpha(1b)-AR. Constitutively activating mutations were introduced into the alpha(1a)-AR at the position homologous to A293 of the alpha(1b)-AR where activating mutations were previously described. Twenty-four alpha-blockers differing in their chemical structures were initially tested for their effect on the agonist-independent inositol phosphate response mediated by the constitutively active A271E and A293E mutants expressed in COS-7 cells. A selected number of drugs also were tested for their effect on the small, but measurable spontaneous activity of the wild-type alpha(1a)- and alpha(1b)-AR expressed in COS-7 cells. The results of our study demonstrate that a large number of structurally different alpha-blockers display profound negative efficacy at both the alpha(1a)- and alpha(1b)-AR subtypes. For other drugs, the negative efficacy varied at the different constitutively active mutants. The most striking difference concerns a group of N-arylpiperazines, including 8-[2-[4-(5-chloro-2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro [4, 5] decane-7,9-dione (REC 15/3039), REC 15/2739, and REC 15/3011, which are inverse agonists with profound negative efficacy at the wild-type alpha(1b)-AR, but not at the alpha(1a)-AR.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1999

Vascular-selective effect of lercanidipine and other 1,4-dihydropyridines in isolated rabbit tissues.

The aim of this study was to characterize the in-vitro vasoselectivity of lercanidipine (in comparison with lacidipine, amlodipine, nitrendipine and felodipine) by evaluating its functional calcium antagonistic activity on rabbit vascular (aorta) and cardiac tissues (heart ventricle). Although incubation with all the compounds tested elicited a concentration-dependent relaxant effect on vascular tissue precontracted with KCl (80 mM), 50% relaxation was reached at different times for each concentration and drug tested. At 10 nM concentration 50% relaxation was reached after 210 min with lercanidipine, 278 min with amlodipine, 135 min with lacidipine, 75 min with nitrendipine and 70 min with felodipine. The onset of the effect was, therefore, similar for lercanidipine, amlodipine and lacidipine, but faster for nitrendipine and felodipine. Similarly, all the compounds tested concentration-dependently reduced the force of cardiac contraction (negative inotropic activity). In this model, the time needed to reach 50% reduction in contractile force was also concentration-dependent, and the ranking order of the speed of onset of the effect (evaluated as the ratio of the IC50 values (the concentrations inhibiting contraction by 50%) calculated after 1 and 4 h incubation) was lacidipine (3.8) > amlodipine (9.6) > felodipine (39) > lercanidipine (68) = nitrendipine (89). The vasoselectivity, expressed as the ratio of the IC50 values obtained on cardiac and vascular tissue, were (for 4 h incubation) 730, 193, 95, 6 and 3 for lercanidipine, lacidipine, amlodipine, felodipine and nitrendipine, respectively, showing that lercanidipine is the most vasoselective of the calcium-antagonists tested. The results show that lercanidipine reduces the inotropic force of the rabbit heart to a lesser extent than do other calcium antagonists, and that this drug had the best heart/vessel selectivity index among the compounds tested at all the times tested.

Animals↗
PubMed1999

Effect of several 5-hydroxytryptamine(1A) receptor ligands on the micturition reflex in rats: comparison with WAY 100635.

Several novel N-arylpiperazine derivatives were synthesized and tested for their 1) affinity and functional activity on 5-hydroxytryptamine(1A) (5-HT(1A)) receptors in vitro; 2) activity in models predictive of antagonism at somatodendritic and postsynaptic 5-HT(1A) receptors; and 3) effects on the micturition reflex in anesthetized and conscious rats. These studies also included 1-(2-methoxyphenyl)-4-[4-(2-phthalimido)butyl] piperazine hydrobromide (NAN 190), 8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4, 5]decane-7,9-dione dihydrochloride (BMY 7378), and N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl-N-(2-pyridinyl)cyclohex anecarboxamide (WAY 100635). Almost all compounds were found to be potent and selective for the human recombinant 5-HT(1A) receptor, with K(i) values in the nanomolar range. [(35)S]GTPgammaS binding in HeLa cells expressing the recombinant human 5-HT(1A) receptor allowed classification of the compounds into neutral antagonists and partial agonists. Almost all neutral antagonists were active in blocking 8-hydroxy-2-dipropylaminotetralin (8-OH-DPAT)-induced forepaw treading in rats (postsynaptic model) and hypothermia in mice (somatodendritic model) with the same potency, whereas compounds showing partial agonistic activity were active in the postsynaptic model but were inactive, or poorly active, in the somatodendritic model. Neutral antagonists potently inhibited volume-induced bladder-voiding contractions in anesthetized rats. Contractions were completely blocked, and the disappearance of bladder contractions lasted 7 to 13 min after the highest doses tested. Furthermore, neutral antagonists increased bladder volume capacity in conscious rats during continuous transvesical cystometry, whereas micturition pressure was only slightly, and not dose-dependently, reduced. Partial agonists were inactive or poorly active, inducing a disappearance time of bladder contractions that did not exceed 6 min in anesthetized rats, and failing to increase bladder volume capacity in conscious rats. These findings indicate that only neutral 5-HT(1A) receptor antagonists are endowed with inhibitory effects on the bladder.

Animals↗
PubMed1999

Identification of local Th2 and Th0 lymphocytes in vernal conjunctivitis by cytokine flow cytometry.

PURPOSE: Th2 lymphocytes may play a key role in the development of allergic diseases such as vernal keratoconjunctivitis (VKC). Cytokine flow cytometry of tear samples was used to identify the phenotypical and functional properties of lymphocytes at the actual site of the allergic reaction. METHODS: Tear and blood samples were obtained from patients affected by active VKC (n = 12) and from normal control subjects (n = 10). Tears were obtained after gentle scraping of the tarsal and bulbar conjunctiva. Tear and blood samples were placed in a solution of brefeldin-A, phorbol myristate acetate (PMA), ionomycin, and RPMI for 4 hours and then processed for flow cytometry. Lymphocytes were marked with the monoclonal antibodies, anti-IFN-gamma and anti-interleukin (IL)-4. Levels of IL-4, IL-2, IFN-gamma, IL-2R, total IgE, eosinophil cationic protein (ECP), eosinophil protein X/neurotoxin (EPX), and myeloperoxidase (MPO) were also evaluated in serum. RESULTS: Expression of IL-4 was observed in 9.2%+/-9.5% of lymphocytes in tears of patients with VKC. Of the 12 patients with VKC, 8 (67%) had tear lymphocytes positive for IL-4 (Th2). Two patients (17%) had a double population of lymphocytes: One was positive for Th2, and the other was positive for both IL-4 and IFN-gamma (Th0). One patient (8%) was positive for IFN-gamma (Th1) only, and one patient was negative for both ILs. No differences in the percentage of Th2 lymphocytes were found between tarsal and limbal patients. The percentage of Th2 lymphocytes was significantly correlated with the severity of the disease. No positive lymphocytes were found in tears of control subjects. Eosinophils, serum IgE, ECP, and EPX were all significantly higher in VKC than in control subjects. CONCLUSIONS: In ocular allergic diseases, local lymphocytes expressed the Th2 phenotype and, to a lesser degree, the Th0 phenotype. Although results of systemic allergic markers can be inconclusive in patients with VKC, flow cytometry demonstrated a local lymphocyte phenotype that can account for the clinical and histologic abnormalities of VKC.

Adult↗
PubMed1998

Design, synthesis, and biological activity of prazosin-related antagonists. Role of the piperazine and furan units of prazosin on the selectivity for alpha1-adrenoreceptor subtypes.

Prazosin-related quinazolines 4-20 were synthesized, and their biological profiles at alpha1-adrenoreceptor subtypes were assessed by functional experiments in isolated rat vas deferens (alpha1A), spleen (alpha1B), and aorta (alpha1D) and by binding assays in CHO cells expressing human cloned alpha1-adrenoreceptor subtypes. The replacement of piperazine and furan units of prazosin (1) by 1, 6-hexanediamine and phenyl moieties, respectively, affording 3-20, markedly affected both affinity and selectivity for alpha1-adrenoreceptor subtypes in functional experiments. Cystazosin (3), bearing a cystamine moiety, was a selective alpha1D-adrenoreceptor antagonist being 1 order of magnitude more potent at alpha1D-adrenoreceptors (pA2, 8.54 +/- 0.02) than at the alpha1A- (pA2, 7.53 +/- 0.01) and alpha1B-subtypes (pA2, 7.49 +/- 0. 01). The insertion of substituents on the furan ring of 3, as in compounds 4 and 5, did not improve the selectivity profile. The simultaneous replacement of both piperazine and furan rings of 1 gave 8 which resulted in a potent, selective alpha1B-adrenoreceptor antagonist (85- and 15-fold more potent than at alpha1A- and alpha1D-subtypes, respectively). The insertion of substituents on the benzene ring of 8 affected, according to the type and the position of the substituent, affinity and selectivity for alpha1-adrenoreceptors. Consequently, the insertion of appropriate substituents in the phenyl ring of 8 may represent the basis of designing new selective ligands for alpha1-adrenoreceptor subtypes. Interestingly, the finding that polyamines 11, 16, and 20, bearing a 1,6-hexanediamine moiety, retained high affinity for alpha1-adrenoreceptor subtypes suggests that the substituent did not give rise to negative interactions with the receptor. Finally, binding assays performed with selected quinazolines (2, 3, and 14) produced affinity results, which were not in agreement with the selectivity profiles obtained from functional experiments. This rather surprising and unexpected finding may be explained by considering neutral and negative antagonism.

Adrenergic alpha-Antagonists↗
PubMed1998

Search for alpha 1-adrenoceptor subtypes selective antagonists: design, synthesis and biological activity of cystazosin, an alpha 1D-adrenoceptor antagonist.

Two novel quinazolines (2 and 3) related to both prazosin and its open analogue 1 were synthesized, and their biological profile at alpha 1-adrenoceptor subtypes was assessed by functional assays in rat isolated tissues, namely prostatic vas deferens (alpha 1A), spleen (alpha 1B) and aorta (alpha 1D). Furthermore, the binding profile of 3 was assessed at native alpha 2 and D2 receptors, and cloned human 5-HT1A receptors, in comparison to prazosin, (+)-cyclazosin, 1 and BMY 7383. It turned out that the cystamine-bearing quinazoline 3 (cystazosin) has a reversed affinity profile relative to (+)-cyclazosin owing to a higher affinity for alpha 1D-adrenoceptors and a significantly lower affinity for the alpha 1A and alpha 1B subtypes. Furthermore, in comparison to BMY 7378, cystazosin (3) displays a much better specificity profile since it has lower affinity for D2 and 5-HT1A receptors.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1998

Mice deficient in nuclear factor (NF)-kappa B/p52 present with defects in humoral responses, germinal center reactions, and splenic microarchitecture.

p52 is a subunit of nuclear factor (NF)-kappa B transcription factors, most closely related to p50. Previously, we have shown that p52, but not p50 homodimers can form transactivating complexes when associated with Bcl-3, an unusual member of the I kappa B family. To determine nonredundant physiologic roles of p52, we generated mice deficient in p52. Null mutant mice were impaired in their ability to generate antibodies to T-dependent antigens, consistent with an absence of B cell follicles and follicular dendritic cell networks in secondary lymphoid organs, and an inability to form germinal centers. Furthermore, the splenic marginal zone was disrupted. These phenotypes are largely overlapping with those observed in Bcl-3 knockout animals, but distinct from those of p50 knockouts, supporting the notion of a physiologically relevant complex of p52 homodimers and Bcl-3. Adoptive transfer experiments further suggest that such a complex may be critical in accessory cell functions during antigen-specific immune reactions. Possible roles of p52 and Bcl-3 are discussed that may underlie the oncogenic potential of these proteins, as evidenced by recurrent chromosomal translocations of their genes in lymphoid tumors.

Adoptive Transfer↗
PubMed1998

Procollagens and inflammatory cytokine concentrations in tarsal and limbal vernal keratoconjunctivitis.

To quantify the presence of inflammatory/fibrogenic cytokines and procollagens type I (PICP) and III (PIIIP) in active and non-active tarsal and limbal forms of vernal keratoconjunctivitis (VKC), tear and blood samples were collected from 27 VKC patients (20 active and 7 non-active) and 15 normal subjects. Upper tarsal conjunctival biopses were obtained from 8 controls and 8 tarsal VKC patients. From biopses of 4 tarsal VKC, fibroblasts were cultured in F12 medium with 10% FCS. TGF-beta 1, IL-1 alpha, IL-1 beta, IL-6 and TNF-alpha, PICP and PIIIP were measured in: (1) tears, (2) homogenized conjunctival tissues, (3) serum, (4) supernatants of tissue cultures at 24 hr, and fibroblast primary passage cultures. Results showed: (1) in tears, TGF-beta 1 and TNF were identified in several active VKC patients without significant differences between the tarsal and the limbal forms. IL-1 beta (27 +/- 51 pg ml-1, P = 0.03) and IL-6 (28 +/- 43 pg ml-1, P = 0.006) were significantly increased in tarsal VKC compared to controls. Both control and non-active VKC tear samples had undetectable levels of all of the above cytokines. PICP and PIIIP were significantly increased in tarsal VKC compared to both limbal VKC and controls. Non-active VKC levels were similar to controls. (2) In homogenized VKC tissues, TGF-beta 1 and IL-6 were both significantly increased compared to controls (P < 0.01) while no increases were observed in IL-1 and TNF-alpha. (3) In serum, IL-1 alpha, IL-1 beta and TNF-alpha were higher in VKC patients compared to controls. (4) In vitro fibroblasts from VKC patients showed an increased production of TGF-beta 1, IL-1 alpha, IL-1 beta, IL-6, TNF-alpha, PICP, and PIIIP over time. Increased levels of TGF-beta 1, IL-1 and IL-6 in VKC tissues and tears indicate a local production of these cytokines in active VKC. Collagen hyperproduction occurs only in active tarsal VKC and may be related to high levels of TGF-beta 1, IL-1 and IL-6. Increased serum levels of IL-1 and TNF-alpha suggests that systemic immunological changes occur in VKC. Cell culture can be used as a model to further study the pathogenesis of VKC and its characteristic local fibroblast activation.

Adolescent↗
PubMed1998

Search for selective antagonists at alpha 1-adrenoreceptors: neutral or negative antagonism?

In this article the use of competitive antagonists as tools in receptor characterization and classification is discussed. It is pointed out that caution is required in receptor characterization because negative antagonism (inverse agonism) rather than neutral antagonism could play a relevant role. This implies that antagonists should be evaluated not only with regard to their affinity, but also with regard to their ability to affect the equilibrium between the two receptor states, namely active and inactive states. Since affinity and efficacy of a negative antagonist are system dependent the use of negative antagonists as competitive antagonists in receptor characterization may give rise to false differences in receptor subtypes. Finally, this article summarizes recent developments in the design of new alpha 1-adrenoreceptor antagonists which are structurally related to prazosin or WB 4101.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1998

Isoxazolo-[3,4-d]-pyridazin-7-(6H)-ones and their corresponding 4,5-disubstituted-3-(2H)-pyridazinone analogues as new substrates for alpha1-adrenoceptor selective antagonists: synthesis, modeling, and binding studies.

A series of phenylpiperazinylalkyl moieties were attached to monocyclic or bicyclic substituted pyridazinones and the new compounds tested for their affinity towards alpha1-adrenoceptor and its alpha1a, alpha1b and alpha1d subtypes, as well as serotonin 5-HT1A receptor. Several analogues (5, 6, 9, and 10) showed remarkable potency and selectivity towards alpha1a, and alpha1d with respect to alpha1b subtype. None of the test compounds exhibited significant affinity for 5-HT1A receptor. Finally, on the basis of the alpha1-AR subtypes 3D models recently proposed, we have elaborated theoretical interaction models for the new compounds. The theoretical study allowed us to predict the affinity of the new compounds as well as to infer the structural/dynamics determinants of their interaction with the three alpha1-AR subtypes.

Adrenergic alpha-Antagonists↗
PubMed1998

Effect of lercanidipine and its (R)-enantiomer on atherosclerotic lesions induced in hypercholesterolemic rabbits.

The in vivo antiatherogenic activity of the calcium antagonist lercanidipine and its (R)-enantiomer was investigated in two different types of atherosclerotic lesions (hyperplastic and fatty-streak lesions) in rabbits. Lercanidipine (0.3, 1, and 3 mg kg(-1) week(-1)) as well as its (R)-enantiomer at 3 mg kg(-1) week(-1) were given by subcutaneous injection for 10 weeks to White New Zealand rabbits, with cholesterol feeding beginning at week 2. The hyperplastic lesion was obtained by positioning a hollow silastic collar around one carotid artery, while aortic fatty streak lesions were induced by cholesterol feeding. In untreated animals (n=5), 14 days after collar positioning an intimal hyperplasia was clearly detectable: the arteries without collar showed a intima/media (I/M) ratio of 0.03+/-0.02, whereas in carotids with a collar the ratio was 2+/-0.42. In lercanidipine-treated animals a significant and dose-dependent effect on intimal hyperplasia was observed. I/M ratios were 0.73+/-0.4, 0.42+/-0.1, 0.32+/-0.1 for 0.3, 1, and 3 mg kg(-1) week(-1), respectively (P<0.05). The lercanidipine enantiomer (3 mg kg(-1) week(-1)) was as effective as the racemate (0.41+/-0.11). Proliferation of smooth muscle cells, assessed by incorporation of BrdU into DNA, was reduced by about 50%, 70%, 85%, and 80% by lercanidipine (0.3, 1, and 3 mg kg(-1) week(-1)) and its (R)-enantiomer, respectively. The area of fatty-streaks in the aorta (n = 11-15) was significantly reduced by lercanidipine (3 mg kg(-1) week(-1), 16% vs 27%, P<0.05), a trend was observed also with lower doses. When different segments of the aorta were considered (arch, thoracic, abdominal) a significant and dose-dependent effect in the thoracic and abdominal aorta was observed also at lower doses. The (R)-enantiomer was as effective as lercanidipine. These results suggest a direct antiatherosclerotic effect of lercanidipine, independent of modulation of risk factors such as hypercholesterolemia and/or hypertension as demonstrated by the absence of stereoselectivity.

Animals↗
PubMed1998

Lercanidipine: short plasma half-life, long duration of action and high cholesterol tolerance. Updated molecular model to rationalize its pharmacokinetic properties.

Calcium-channel antagonist drugs of the 1,4-dihydropyridine type have been shown to bind to the L-type calcium channel. These drugs are not only amphiphilic, but new molecular designs have become increasingly lipophilic and can readily transport across cell membranes, accessing both hydrophilic and hydrophobic environments, despite becoming more soluble in the membrane bilayer. This biophysical understanding appears not only to define the molecular pathways for drug binding to the calcium-channel receptor, but also to explain differences in the overall clinical pharmacokinetics observed for different drugs in this class. The pharmacokinetic profile of calcium antagonists, although influenced to some degree by interactions with their target calcium-channel receptor, appears to be largely dictated by their interactions with cell membranes at the molecular level. There appears to be a correlation between the duration of action of such membrane-active drugs and the membrane partition coefficient in conjunction with the washout rate. This class of drugs has evolved from a drug such as amlodipine, with a long duration of action related to prolonged plasma half-life, to lercanidipine, which has the shortest plasma half-life relative to its intrinsically long duration of action. Recently, it was discovered that membrane cholesterol reduces the amount of calcium-channel antagonist that can partition into the membrane. Atherosclerotic disease results in increased levels of membrane cholesterol in smooth muscle cells. Latest generation calcium antagonist, which have a long duration of action, can better overcome this negative effect. Lercanidipine has now been shown to have one of the highest measured tolerances to cholesterol, which may indicate its ability to treat a broad range of hypertensive patients with varying degrees of progressive atherosclerotic disease. On what criteria should the effectiveness of calcium antagonists be evaluated? A good calcium antagonist needs to exhibit a placebo-like side-effect profile, thus ensuring good patient compliance. However, an intrinsically long-lasting, once-a-day dose is also pharmacokinetically desirable. To be a truly optimal calcium antagonist, it should function and be efficacious over a broad range of hypertensive patients. It should be able to control blood pressure in light of other complications such as progressive atherosclerotic disease. Recent studies indicate that during the progression of atherosclerosis, cholesterol levels within cell membranes of the arterial wall increase, a process that can reduce the effective concentration of calcium antagonists in these membranes. What is needed is a calcium antagonist that is slow acting to reduce vasodilatory induced side-effects and intrinsically long lasting to ensure once-a-day dosage, and that possesses a high cholesterol tolerance factor to overcome the molecular and compositional changes taking place in the arterial wall, so that it can treat effectively a broad range of hypertensive patients.

Animals↗
PubMed1997

Requirement for NF-kappaB in osteoclast and B-cell development.

NF-kappaB is a family of related, dimeric transcription factors that are readily activated in cells by signals associated with stress or pathogens. These factors are critical to host defense, as demonstrated previously with mice deficient in individual subunits of NF-kappaB. We have generated mice deficient in both the p50 and p52 subunits of NF-kappaB to reveal critical functions that may be shared by these two highly homologous proteins. We now demonstrate that unlike the respective single knockout mice, the p50/p52 double knockout mice fail to generate mature osteoclasts and B cells, apparently because of defects that track with these lineages in adoptive transfer experiments. Furthermore, these mice present markedly impaired thymic and splenic architectures and impaired macrophage functions. The blocks in osteoclast and B-cell maturation were unexpected. Lack of mature osteoclasts caused severe osteopetrosis, a family of diseases characterized by impaired osteoclastic bone resorption. These findings now establish critical roles for NF-kappaB in development and expand its repertoire of roles in the physiology of differentiated hematopoietic cells.

Animals↗