Is a flavonoid-rich diet with steamer cooking safe during calcineurin inhibitors therapy?

WHAT IS KNOWN AND OBJECTIVE

Dietary therapy is recommended for decreasing the symptoms of the metabolic syndrome and the risk of type 2 diabetes and cardiovascular diseases in subjects on calcineurin inhibitors. However, food-drug interactions may occur particularly with patients on such immunosuppressive therapy. This article comments on the benefit/risk assessment of a flavonoid-rich diet and steam-cooking of such food during calcineurin inhibitors therapy.

COMMENT

Patients are commonly advised against consuming citrus fruits and juices, grape juice and green tea. High vegetable intake may however increase the risk of food-diet interactions by inhibiting drug metabolic enzymes and transporters. Vegetable glucosinolates are potential interactants and may lead to adverse effects of drugs with narrow therapeutic indices and in the presence of genetic polymorphism. Examples of food components with potential drug interactants include all members of the Brassicaceae family.

WHAT IS NEW AND CONCLUSION

The potential additive and synergistic effects of flavonoids with other molecules in interfering with drug bioavailability need to be taken into account. The risk is highest with drugs with a narrow therapeutic index and in subjects with genetic polymorphisms of proteins involved in the disposition of those drugs.

Control of matrix metalloproteinase production in human intestinal fibroblasts by interleukin 21

BACKGROUND

T cell-mediated immunity plays a central part in the pathogenesis of tissue damage in inflammatory bowel disease (IBD). The mechanism by which T cells mediate tissue damage during IBD remains unclear, but evidence indicates that T cell-derived cytokines stimulate fibroblasts to synthesise matrix metalloproteinases (MMPs), which then mediate mucosal degradation. We have previously shown that, in IBD, there is high production of interleukin (IL) 21, a T cell-derived cytokine, which enhances Th1 activity.

AIM

To investigate whether IL21 controls MMP production by intestinal fibroblasts.

METHODS

IL21 receptor (IL21R) was evaluated in intestinal fibroblasts by reverse transcriptase-polymerase chain reaction (RT-PCR) and western blotting. Fibroblasts were stimulated with IL21 and MMPs were evaluated by RT-PCR and western blotting. The effect of a neutralising IL21R fusion protein (IL21R/Fc) on the induction of MMPs in fibroblasts stimulated with IBD lamina propria mononuclear cell (LPMC) supernatants was also evaluated.

RESULTS

Intestinal fibroblasts constitutively express both IL21R and the common gamma chain receptor, which are necessary for IL21-driven signalling. IL21 enhances fibroblast production of MMP-1, MMP-2, MMP-3 and MMP-9, but not tissue inhibitors of MMP-1 and MMP-2. Moreover, IL21 synergises with tumour necrosis factor alpha to increase synthesis of MMP synthesis. IL21 enhances MMP secretion without affecting gene transcription and protein synthesis. IBD LPMC supernatants stimulate MMP secretion by intestinal fibroblasts, and this effect is partly inhibited by IL21R/Fc.

CONCLUSIONS

These results suggest that fibroblasts are a potential target of IL21 in the gut and that IL21 controls MMP secretion by fibroblasts.

Oxidant-induced pHi/Ca2+ changes in rat aortic smooth muscle cells. The role of atrial natriuretic peptide

The aim of this study was to investigate the effects of oxidative stress on PLD activity, [Ca2+]i and pHi levels and the possible relationship among them. Moreover, since atrial natriuretic peptide (ANP) protects against oxidant-induced injury, we investigated the potential protective role of the hormone in rat aortic smooth muscle (RASM) cells exposed to oxidative stress. Water-soluble 2,2'-Azobis (2-amidinopropane) dihydrochloride (AAPH) was used as free radical generating system, since it generates peroxyl radicals with defined reaction and the half time of peroxyl radicals is longer than other ROS. A significant increase of PLD activity was related to a significant decrease in pHi, while [Ca2+]i levels showed an increase followed by a decrease after cell exposure to AAPH. [Ca2+]i changes and pHi fall induced by AAPH were prevented by cadmium which inhibits a plasma membrane Ca2+ ATPase coupled to Ca2+/H+ exchanger, that operates the efflux of Ca2+ coupled to H+ influx. The involvement of PLD in pHi and [Ca2+]i changes was confirmed by calphostin-c treatment, a potent inhibitor of PLD, which abolished all AAPH-induced effects. Pretreatment of RASM cells with pharmacological concentrations of ANP attenuated the AAPH effects on PLD activity as well as [Ca2+]i and pHi changes, while no effects were observed with physiological ANP concentrations, suggesting a possible role of the hormone as defensive effector against early events of the oxidative stress.

Role of the cholinergic system and of apamin-sensitive Ca2+-activated K+ channels on rabbit jejunum spontaneous activity and on the inhibitory effects of adrenoceptor agonists

1. One reason why rabbit jejunum is suitable for studying the mechanisms underlying the actions of the various neurotransmitters and their interactions is its spontaneous motility. The main regulator of spontaneous motility is the cholinergic system. How the cholinergic system regulates the spontaneous activity in the rabbit jejunum and how it affects the inhibitory action of alpha- and beta-adrenoceptor agonists remains unclear. 2. We studied the influence of the cholinergic system and apamin-sensitive Ca2+-activated K+ channels on spontaneous contractions in the rabbit jejunum and on the inhibitory effects of alpha1- and beta-adrenoceptor agonists. 3. In naïve tissues, atropine (ATR, 7.4 x 10(-8) m) and tetrodotoxin (8 x 10(-8) m) almost completely inhibited - to a similar extent - the amplitude of spontaneous activity. Despite the presence of ATR or TDX, tissue contraction gradually recovered to about 50% of the baseline amplitude within 5-10 min. When ATR or TDX, respectively, were added to the TDX- or ATR-treated tissues, the recovered activity decreased weakly but significantly. After washout and a 45-min rest the contraction amplitude returned to baseline values. A further exposure to ATR or TDX reduced the contraction to a level significantly lower than the one obtained after TDX or ATR added 5 min after ATR or TDX, respectively. In preparations prestimulated for 10 min with acetylcholine (ACh), ATR abolished the TDX-resistant recovered spontaneous activity. 4. Adrenaline (ADR, 0.5-5 x 10(-7) m) and phenylephrine (PHE, 1-10 x 10(-7) m) inhibited tissue motility in naïve and in ATR- and in TDX-exposed preparations. But whereas in naïve preparations the alpha1-adrenoceptor antagonists completely antagonized inhibition induced by both drugs, in ATR- and TDX-exposed tissues they did so only partially for ADR. Agonist-induced inhibition had a rapid onset but rapidly faded; pendular movements took significantly longer to recover in ATR- and TDX-treated tissues than in naïve tissues. In tissues exposed for 2 min to ADR (0.5-5 x 10(-7) m) or PHE (1-10 x 10(-7) m), washout or addition of alpha1-adrenoceptor antagonists caused an immediate short-lasting increase in contraction amplitude. 5. Apamin (APAM, 5 x 10(-9) m) caused a rapid and persistent increase in the amplitude of contractions. It also blocked the inhibitory responses to ADR and PHE, and removed washout-induced contractions. The APAM-induced increase in the contraction amplitude correlated with the increase obtained by washing out ADR or PHE. 6. Isoprenaline (at concentrations up to 2.8 x 10(-7) m) produced no inhibitory response in naïve tissues, but it invariably blocked (at a concentration of 0.7 x 10(-7) m) the recovered spontaneous activity (and sometimes depressed muscletone) in tissues exposed to ATR or TDX. Neither propranolol (3.4 x 10(-7) m) nor APAM (5 x 10(-9) m) counteracted these inhibitory effects. 7. These results indicate that spontaneous motility in the rabbit jejunum is predominantly mediated by neuronal release of ACh and by some other unidentified neuronal activity. Released ACh inhibits myogenic activity and strongly antagonizes beta-adrenoceptor-induced APAM-insensitive inhibition but leaves alpha1 agonist-induced APAM-sensitive inhibition unchanged.

The clot gene of Drosophila melanogaster encodes a conserved member of the thioredoxin-like protein superfamily

The conversion of pyruvoyl-H(4)-pterin to pyrimidodiazepine (PDA), which is an essential step in the biosynthesis of the red components of Drosophila eye pigments known as drosopterins, requires the products of the genes sepia and clot. While the product of sepia has been shown to correspond to the enzyme PDA-synthase, the role of clot remains unknown, although the clot(1) allele was one of the first eye-color mutants to be isolated in Drosophila melanogaster,and much genetic and biochemical data has become available since. Here we report the cloning of the clot gene, describe its molecular organization and characterize the sequence alterations associated with the alleles cl(1) and cl(2). The coding properties of the gene show that it encodes a protein related to the Glutaredoxin class of the Thioredoxin-like enzyme superfamily, conserved members of which are found in human, mouse and plants. We suggest that the Clot protein is an essential component of a glutathione redox system required for the final step in the biosynthetic pathway for drosopterins.

Functional analysis of regulatory elements controlling the expression of the ecdysone-regulated Drosophila ng-1 gene

The steroid hormone ecdysone controls multiple aspects of insect development, including larval moults and metamorphosis, and can induce specific genetic responses in different tissues. The definition of the molecular mechanisms able to mediate this tissue-specific responsiveness may greatly contribute to understanding how such an accurate genetic response is achieved. In this work we have identified, by transgenic analysis, the regulatory elements directing the expression of ng-1, an ecdysone-regulated Drosophila gene showing a highly specific developmental expression profile. Our results show that an ecdysone-responsive element located within the ng-1 coding region is necessary for high-level gene expression, whereas the gene's spatial and temporal expression profile is fully controlled by a distinct upstream regulatory region. This region binds a set of transcriptional factors, including the FKH regulatory protein, which can potentially modulate the ecdysone genetic regulated response.

minifly, a Drosophila gene required for ribosome biogenesis

We report here the genetic, molecular, and functional characterization of the Drosophila melanogaster minifly (mfl) gene. Genetic analysis shows that mfl is essential for Drosophila viability and fertility. While P-element induced total loss-of-function mutations cause lethality, mfl partial loss-of-function mutations cause pleiotropic defects, such as extreme reduction of body size, developmental delay, hatched abdominal cuticle, and reduced female fertility. Morphological abnormalities characteristic of apoptosis are found in the ovaries, and a proportion of eggs laid by mfl mutant females degenerates during embryogenesis. We show that mfl encodes an ubiquitous nucleolar protein that plays a central role in ribosomal RNA processing and pseudouridylation, whose known eukaryotic homologues are yeast Cfb5p, rat NAP57 and human dyskerin, encoded by the gene responsible for the X-linked dyskeratosis congenita disease. mfl genetic analysis represents the first in vivo functional characterization of a member of this highly conserved gene family from higher eukaryotes. In addition, we report that mfl hosts an intron encoded box H/ACA snoRNA gene, the first member of this class of snoRNAs identified so far from Drosophila.

The Ceratitis capitata homologue of the Drosophila sex-determining gene sex-lethal is structurally conserved, but not sex-specifically regulated

In Drosophila, Sxl functions as a binary switch in sex determination. Under the control of the primary sex-determining signal, it produces functional protein only in XX animals to implement female development. Here we report that, in contrast to Drosophila, the Sxl homologue in the Medfly, Ceratitis capitata, expresses the same mRNAs and protein isoforms in both XX and XY animals irrespective of the primary sex-determining signal. Also, experiments with two inducible transgenes demonstrate that the corresponding Ceratitis SXL product has no significant sex-transforming effects when expressed in Drosophila. Similar results have been obtained for the Sxl homologue of Musca domestica (Meise, M., Hilfiker-Kleiner, D., Brunner, C., DLbendorfer, A., N?thiger, R. and Bopp, D. (1998) Development 125, 1487–1494). Our findings suggest that Sxl acquired its master regulatory role in sex determination during evolution of the Acalyptratae group, most probably after phylogenetic divergence of the genus Drosophila from other genera of this group.

An extensive search for RFLP in the human glucose-6-phosphate dehydrogenase locus has revealed a silent mutation in the coding sequence

The genetic polymorphism of an approximately 100-kb DNA region comprising and flanking the glucose-6-phosphate dehydrogenase (G6PD) gene on human chromosome Xq28 has been analyzed in detail. By using 14 unique sequence probes and 18 restriction enzymes, we have characterized 257 restriction fragments or 370 restriction sites. On testing 12-57 individual X chromosomes, all sites but one were nonpolymorphic. However, a PstI site that maps to exon 10 of the G6PD gene, which is still monomorphic in all British and Italian subjects tested, is polymorphic in west-African people. Specifically, it is absent from 22% of Nigerian X chromosomes. By sequence analysis we have shown that the absence of this PstI site results from a G----A replacement at position 1116, corresponding to the third base of a glutamine codon; no amino acid change is produced in the protein. Thus, a polymorphic silent mutation is demonstrated in a human gene.

Insulin resistance, acanthosis nigricans, and polycystic ovaries associated with a circulating inhibitor of postbinding insulin action

A 21-yr-old moderately obese woman with hirsutism, acanthosis nigricans, and oligomenorrhoea was diagnosed as having polycystic ovary syndrome. Despite hyperinsulinemia, binding of insulin to her red cells was within the range for normal, young adult subjects. Her serum did not bind or degrade [125I]insulin or alter its binding to fat cells, and was negative for insulin receptor antibodies. However, her serum caused a dose-dependent inhibition of insulin-stimulated lipogenesis (conversion of [3-3H]glucose to [3H]lipid) in rat fat cells significantly greater than that produced with control serum (relative potency, 3.5:1) and (at a 1:20 dilution) markedly impaired the response of both lipogenesis and 2-deoxy-D-glucose uptake to maximum concentrations of insulin. After the patient was treated with clomiphene for 4 months, her menses resumed, hair growth slowed, fasting blood glucose and plasma insulin concentrations decreased, and serum inhibitory activity decreased to the control range. Serum inhibitory activity was stable to freezing and thawing and to heating at 56 C for 30 min, and could be extracted into acid-ethanol. By dialysis, its mol wt was below 1000, whereas by ultracentrifugation, it was above 3500; both high and low mol wt forms were detected after Sephadex G-50 gel chromatography of serum, suggesting that the inhibitor was of low mol wt but loosely bound to a higher mol wt component in serum. These findings indicate that insulin resistance in this patient with acanthosis nigricans and polycystic ovaries could be attributed to a circulating low mol wt inhibitor of postbinding insulin action.

A postbinding inhibitor of insulin action. Increased concentrations in the plasma of non-insulin-dependent diabetic subjects

"Postreceptor" insulin resistance in persons with non-insulin-dependent diabetes (NIDDM) could be due to an intrinsic defect in insulin-sensitive pathways or to the action of a circulating inhibitor. Since evidence for the former is lacking, we have addressed the question of a circulating inhibitor by examining the effect of plasma and plasma extracts from NIDDM subjects on the lipogenic response of rat adipocytes to insulin. A majority (77%) of plasma samples (1:20 dilution) from unselected, treated NIDDM subjects (N = 69) inhibited insulin-stimulated conversion of 3-3H-glucose to 3H-lipid in rat adipocytes to a greater extent than did control samples (N = 24). The mean +/- SD inhibition by NIDDM plasma (81 +/- 21%) was significantly greater (P less than 0.01) than by control plasma (50 +/- 14%). Diabetic and, to a lesser degree, control plasma both caused a significant decrease in the maximal response of lipogenesis to insulin. Inhibitory activity was extracted into acid/ethanol, present in the flow of a Sep-pak C18 column, heat-stable (56 degrees C for 30 min [plasma], 80 degrees C for 30 min [acid/ethanol]), resistant to proteases, and dialyzable through 1000-dalton-mol wt exclusion dialysis tubing. The inhibition by NIDDM plasma or partially purified inhibitor could not be explained by the presence of insulin antibodies, insulin receptor antibodies, other inhibitors of insulin binding, or the concentrations of known counterregulatory factors. There was no correlation between inhibitory activity and plasma glucose (r = 0.26), insulin (r = 0.33), C-peptide (r = 0.26), or HbA1c (r = 0.26).(ABSTRACT TRUNCATED AT 250 WORDS)