A synthetic triterpenoid, 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO), is a ligand for the peroxisome proliferator-activated receptor gamma

A novel synthetic triterpenoid, 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO), previously reported to have potent differentiating, antiproliferative, and antiinflammatory activities, has been identified as a ligand for the peroxisome proliferator-activated receptor gamma (PPARgamma). CDDO induces adipocytic differentiation in 3T3-L1 cells, although it is not as potent as the full agonist of PPARgamma, rosiglitazone. Binding studies of CDDO to PPARgamma using a scintillation proximity assay give a Ki between 10(-8) to 10(-7) M. In transactivation assays, CDDO is a partial agonist for PPARgamma. The methyl ester of CDDO, CDDO-Me, binds to PPARgamma with similar affinity, but is an antagonist. Like other PPARgamma ligands, CDDO synergizes with a retinoid X receptor (RXR)-specific ligand to induce 3T3-L1 differentiation, while CDDO-Me is an antagonist in this assay. The partial agonism of CDDO and the antagonism of CDDO-Me reflect the differences in their capacity to recruit or displace cofactors of transcriptional regulation; CDDO and rosiglitazone both release the nuclear receptor corepressor, NCoR, from PPARgamma, while CDDO-Me does not. The differences between CDDO and rosiglitazone as either partial or full agonists, respectively, are seen in the weaker ability of CDDO to recruit the coactivator CREB-binding protein, CBP, to PPARgamma. Our results establish the triterpenoid CDDO as a member of a new class of PPARgamma ligands.

Biotransformation of lantadene A (22 beta-angeloyloxy-3-oxoolean-12-en-28-oic acid), the pentacyclic triterpenoid, by Alcaligenes faecalis

A bacterial strain capable of biotransformation of lantadene A (22 beta-angeloyloxy-3-oxo-olean-12-en-28-oic acid), the pentacyclic hepatotoxin of lantana (Lantana camara var. aculeata) has been isolated from soil using lantadene A as the sole carbon source. The organism is Gram negative, rod shaped, motile, catalase positive and has been identified as Alcaligenes faecalis. The isolate has been found to be specific for lantadene A and did not utilize lantadene B. In studies using sucrose as an additional carbon source, A. faecalis elicited biotransformation of lantadene A to its trans isomer 22 beta-tigloyloxy-3-oxoolean-12-en-28-oic acid, designated as lantadene X and two other minor metabolites which could not be isolated in pure state.

Disposition of lantadene A, the pentacyclic triterpenoid hepatotoxin, orally administered to guinea pigs

Lantadene A (LA) administered orally to guinea pigs elicited cholestasis. LA could not be detected in liver, bile, gall bladder, blood and urine. LA and its biotransformation product reduced lantadene A (RLA) could be detected in caecum, large intestine, and faeces. In vitro incubation of LA with liver homogenates under aerobic and anaerobic conditions did not elicit its biotransformation to RLA. On the other hand, in vitro incubation of LA with guinea pig caecal and large intestinal contents under anaerobic conditions elicited conversion of LA to RLA. This is the first report of the biotransformation of LA in the animal system.

Binding characterization of [3H]S-0139, an antagonist of the endothelin ET(A) receptor subtype

S-0139 (27-O-3-[2-(3-carboxy-acryloylamino)-5-hydroxyphenyl]-acryloylo xy myricerone, sodium salt) is a highly specific nonpeptide endothelin ET(A) receptor antagonist. The binding of [3H]S-0139 was compared to that of [125I]endothelin-1 to characterize the binding of the antagonist in porcine aortic smooth muscle membranes. Scatchard analysis revealed a single class of [3H]S-0139 binding sites with a Kd value of 0.61 +/- 0.10 nM and a Bmax of 0.72 +/- 0.16 pmol/mg protein. These sites were saturable and reversible. [125I]Endothelin-1 also showed binding with high affinity (Kd = 0.12 +/- 0.02 nM) to a homogeneous population of binding sites, whose Bmax (0.71 +/- 0.20 pmol/mg protein) was almost the same as that for [3H]S-0139. In both cases, the binding could be displaced by known endothelin receptor ligands and their IC50 values in each case showed a very close correlation (r = 0.986). The potency of seven endothelin receptor antagonists to displace [3H]S-0139 binding also correlated highly to the potency for inhibiting the endothelin-1-induced increase in cytosolic Ca2+ concentration (r = 0.949). Myriceric acid A showed a more potent functional activity than expected from its binding affinity, but this seemed to result from the different assay conditions, such as incubation time. Together, the results suggest that S-0139 labels only endothelin ET(A) receptor binding sites in porcine aortic smooth muscle.

Specificity of the tonoplast transport of the oleanolic acid monoglycosides in the vacuoles from Calendula officinalis leaves

The specificity of two separate tonoplast permeases transporting oleanolic acid glycosides was investigated in vacuoles isolated from leaf protoplasts of marigold (Calendula officinalis) with the use of chemically synthesized analogs. The results indicate that the proper structure of both parts of oleanolic acid monoglycoside, i.e. aglycon and the sugar moiety, are required for binding to a specific tonoplast carrier.

Biodegradation of lantadene A, the pentacyclic triterpenoid hepatotoxin by Pseudomonas pickettii

A bacterial strain capable of biodegradation of lantadene A (22 beta-angeloyloxy-3-oxoolean-12-en-28-oic acid) has been isolated from soil using lantadene A as the sole carbon source. The organism is rod shaped, Gram negative, motile and has been identified as Pseudomonas pickettii. This is the first report of the biodegradation of a pentacyclic triterpenoid.

Reversibility of the oleanolic acid monoglycosides transport across the tonoplast in vacuoles isolated from Calendula officinalis leaves

The possibility of the reversible tonoplast transport of oleanolic acid monoglycosides was investigated in vacuoles isolated from Calendula officinalis leaf protoplasts. The obtained results point to the reversibility of the transport of monoglucoside I, whereas monoglucuronide F seems to be definitely stored in the vacuolar space.