In vitro effect of retinoids on calcineurin activity

Identification of alkylbenzene sulfonate surfactants leaching from an acrylonitrile butadiene rubber as novel inhibitors of calcineurin activity

Calcineurin (CN) is a Ca(2+)/calmodulin (CaM) dependent serine/threonine protein phosphatase and plays important role in several cellular functions in both higher and lower eukaryotes. Here we report inhibition of CN by linear alkylbenzene sulfonate. The clue to the finding was obtained while identifying the inhibitory material leaching from acrylonitrile butadiene rubber used for packing. Using standard dodecylbenzene sulfonate (C12-LAS), we obtained strong inhibition of CN with a half maximal inhibitory concentration of 9.3 µM, whereas analogs such as p-octylbenzene sulfonate and SDS hardly or only slightly affected CN activity. Three alkaline phosphatases, derived from shrimp, bacteria, and calf-intestine, which exhibit similar enzymatic activities to CN, were not inhibited by C12-LAS at concentrations of up to 100 µM. Furthermore, C12-LAS did not inhibit Ca(2+)/CaM-dependent myosin light chain kinase activity when tested at concentrations of up to 36 µM. The results indicate that C12-LAS is a potent selective inhibitor of CN activity.

Synthesis of optically pure norcantharidin analogue NCA-01, a highly selective protein phosphatase 2B inhibitor, and its derivatives

An efficient synthetic route to optically pure norcantharidin analogue NCA-01, a highly selective inhibitor of protein phosphatase 2B (PP2B; calcineurin), has been developed. The absolute stereochemistry of the enantiomers was determined by X-ray crystallographic analysis. Optically pure NCA derivatives that had various substituents at the C1 position were synthesized in a similar manner. The PP2B-inhibitory activities of NCA-01 and its derivatives were independent of the enantiomeric form. NCA-01 dimethyl ester potently inhibited IL-2 production in Jurkat cells.

Inhibition of calcineurin by polyunsaturated lipids

From earlier studies on calcineurin, the presence of multiple double bonds in putative inhibitors was hypothesized as critical features for effective inhibition. Polyunsaturated fatty acids were tested as inhibitors of calcineurin and found to inhibit the phosphatase activity of calcineurin although effective inhibition was observed only in the absence of calmodulin. Calmodulin and fatty acids seemed to compete for the enzyme with the activation curve of calmodulin shifted approximately 100-fold in the presence of 50 microM eicosa-11Z,14Z-dienoic acid (20:2, n-6) or 50 microM eicosa-8Z,11Z,14Z-trienoic acid (20:3, n-6). Leukotriene B4 and derivatives also were screened as inhibitors. The most effective inhibition was caused by the 6-trans,12-epi-leukotriene B4 with an IC50 of 16.4 microM for the inhibition of calcineurin with pNPP as the substrate. Lipoxins A4 and B4 likewise caused inhibition in the presence of calmodulin with an IC50 of 42.7 microM for lipoxin B4. There was no protection by calmodulin, as found with the inhibition by the fatty acids. These data support the hypothesis that effective inhibition is bolstered by the presence of conjugated double bonds in the inhibitor. Consideration of cis- and trans-orientation of the double bonds suggests that presentation of the delocalized electron density is also a factor in effective inhibition of calcineurin.

Moderate maternal vitamin A deficiency alters myogenic regulatory protein expression and perinatal organ growth in the rat

Vitamin A deficiency is one of the most common dietary deficiencies in the developing world and is a major health concern where it is associated with increased risk of fetal and infant mortality and morbidity. Early studies in the rat demonstrated that, in addition to respiratory problems, neonates showed evidence of mobility problems in response to moderate vitamin A deficiency. This study investigated whether moderate deficiency of this vitamin plays a role in regulating key skeletal muscle regulatory pathways during development. Thirty female rats were fed vitamin A-moderate (VAM) or vitamin A-sufficient diets from weaning and throughout pregnancy. Fetal and neonatal hindlimb and muscle samples were collected on days 13.5, 15.5, 17.5, and 19.5 of pregnancy and 1 day following birth. Mothers fed the VAM diet had reduced retinol concentrations at all time points studied (P < 0.01), and neonates had reduced relative lung weights (P < 0.01). Fetal weight and survival did not differ between groups but neonatal survival was lower in the VAM group where neonates had increased relative heart weights (P < 0.05). Analysis of myogenic regulatory factor expression and calcineurin signaling in fetuses and neonates demonstrated decreased protein levels of myf5 [50% at 17.5 dg (P < 0.05)], myogenin [70% at birth (P < 0.001)], and myosin heavy chain fast [50% at birth (P < 0.05)] in response to moderate vitamin A deficiency. Overall, these changes suggest that vitamin A status during pregnancy may have important implications for fetal muscle development and subsequent muscle function in the offspring.