High-performance liquid chromatographic-nuclear magnetic resonance investigation of the isomerization of alachlor-ethanesulfonic acid.

The metabolism of the acetanilide herbicide alachlor in soils leads to the formation of alachlor-ethanesulfonic acid (alachlor-ESA) as one of the major transformation products of this compound. The unique structure of alachlor and its metabolites allows the formation of two diastereomers (s-trans and s-cis) due to the hindered rotation of the amide bond connected to a rigid aromatic ring. Although these stereoisomers do interconvert by rotation about the amide bond, the rate of interconversion is slow allowing separation of the isomers on the chromatographic time scale. Once separated, the unique nuclear magnetic resonance signals of each isomer can be used to monitor the rate of isomerization. This paper reports the on-line separation and detection of the rotational diastereomers using high-performance liquid chromatography-nuclear magnetic resonance (HPLC-NMR) to efficiently measure the isomerization rate of alachlor-ESA.

Dual roles for lipolysis and oxidation in peroxisome proliferation-activator receptor responses to electronegative low density lipoprotein.

Low density lipoprotein (LDL) exists in various forms that possess unique characteristics, including particle content and metabolism. One circulating subfraction, electronegative LDL (LDL(-)), which is increased in familial hypercholesterolemia and diabetes, is implicated in accelerated atherosclerosis. Cellular responses to LDL(-) remain poorly described. Here we demonstrate that LDL(-) increases tumor necrosis factor alpha (TNFalpha)-induced inflammatory responses through NF kappa B and AP-1 activation with corresponding increases in vascular cell adhesion molecule-1 (VCAM1) expression. LDL receptor overexpression increased these effects. In contrast, exposing LDL(-) to the key lipolytic enzyme lipoprotein lipase (LPL) reversed these responses, inhibiting VCAM1 below levels seen with TNFalpha alone. LPL is known to act on lipoproteins to generate endogenous peroxisomal proliferator-activated receptor alpha (PPAR alpha) ligand, thus limiting inflammation. These responses varied according to the lipoprotein substrate triglyceride content (very low density lipoprotein >> LDL > high density lipoprotein). The PPAR alpha activation seen with LDL, however, was disproportionately high. We show here that MUT LDL activates PPAR alpha to an extent proportional to its LDL(-) content. As compared with LDL(-) alone, LPL-treated LDL(-) increased PPAR alpha activation 20-fold in either cell-based transfection or radioligand displacement assays. LPL-treated LDL(-) suppressed NF kappa B and AP-1 activation, increasing expression of the PPAR alpha target gene I kappa B alpha, although only in the genetic presence of PPAR alpha and with intact LPL hydrolysis. Mass spectrometry reveals that LPL-treatment of either LDL or LDL(-) releases hydroxy-octadecadienoic acids (HODEs), potent PPAR alpha activators. These findings suggest LPL-mediated PPAR alpha activation as an alternative catabolic pathway that may limit inflammatory responses to LDL(-).