Macrophages were infected with virulent B. abortus strain 2308 or attenuated strain 19. Intracellular bacteria were recovered at different times after infection and their proteomes compared. The virulent strain initially reduced most biosynthesis and altered its respiration, adaptations reversed later in infection. The attenuated strain was unable to match the magnitude of the virulent strain’s adjustments. The results provide insight into mechanisms utilized by Brucella to establish intracellular infections.

Oxidative stress is a cardinal manifestation of various intestinal disorders. However, very little knowledge is available on the intestine's inherent defense mechanisms against free radicals. This study was designed to determine the protein expression, subcellular localization and oxidative stress response of paraoxonase 2 (PON2), a member of a powerful antioxidant family in human and rat intestine. Biochemical and ultrastructural experiments all showed a substantial expression of PON2 in human and rat intestine. Western blot analysis disclosed higher levels of PON2 in the jejunum than in the duodenum, ileum, and colon. Cell fractionation revealed a predominant PON2 association with microsomes and lysosomes in the human jejunum, which differed from that in rats. PON2 was detected in the intestine as early as week 15 of gestation and was significantly increased by week 20. Iron ascorbate-mediated lipid peroxidation induced a marked decrease in PON2 expression in intestinal specimens coincidental to an abundant rise in malondialdehyde (MDA). On the other hand, preincubation with potent antioxidants, such as butylated hydroxytoluene, Trolox, and N-acetylcysteine, prevented iron-ascorbate-generating PON2 reduction in parallel with MDA suppression. Finally, the preincubation of permeabilized Caco-2 cells with purified PON2 led to a protection against iron-ascorbate-induced lipid peroxidation. These observations demonstrate that the human intestine is preferentially endowed with a marked PON2 expression compared with the rat intestine and this expression shows a developmental and intracellular pattern of distribution. Furthermore, our observations suggest PON2 protective effects against prooxidant stimuli in the small intestine.

Paraoxonase 1 (PON1) is a serum enzyme closely associated with high-density lipoprotein (HDL), which may protect against atherosclerosis by hydrolyzing lipid peroxides and several organophosphorus compounds. The purpose of the present study was to test the hypothesis that lipid peroxidation modifies the activity and protein mass of PON1 in humans and rats. Our findings revealed that the bulk of the activity monitored by the hydrolysis of paraoxon and phenyl acetate was confined to liver intracellular endoplasmic reticulum-derived microsomes and was mostly recovered in circulating HDL3. Confirmation was obtained by the determination of PON1 expression by Western blot. It is noteworthy that PON1 levels were consistently decreased in human sera, HDL, and liver microsomes compared with rat counterparts. Concomitant with iron-ascorbate-mediated lipid peroxidation, there was a decline in PON1 activity and protein in both HDL3 and microsomes, which was attenuated by butylated hydroxytoluene antioxidant treatment. The current data indicate that PON1 localization in microsomes and HDL3 could represent a selective cellular and lipoprotein response to oxidative stress. This was tested by the iron-ascorbate oxygen-radical generating system. It is also proposed that the increased PON1 level may have a function related to the well-known atherosclerosis resistance of rats.