Prostaglandins (PG) are important modulators of immune and inflammatory responses. We recently demonstrated that the production of PGD 2 by the helminthic parasite Schistosoma mansoni inhibits the migration of epidermal Langerhans cells (LC) to the draining lymph nodes (DLN). Here, we identify the responsible parasite enzyme as being a 28-kDa glutathione-S-transferase (termed Sm28GST). Intradermal injection of Sm28GST in wildtype (WT), but not in D prostanoid receptor (DP) 1-deficient mice abrogates the departure of LC from the epidermis after TNF- § or FITC treatment. During infection, DP1 deficiency restores LC migration, but does not enhance the rate of T cell proliferation in the skin DLN. However, relative to WT mice, DLN cells from DP1-deficient infected mice produce dramatically less IFN-+ and IL-10, but equal amount of IL-4. Interestingly, infected DP1-deficient mice develop a more Th2-biased humoral immune response, a significantly reduced parasitemia and a decreased egg-induced inflammatory response in the liver and intestines. Taken together, we propose that DP1 activation by the Sm28GST-derived PGD 2 could represent a strategy for the schistosome to evade host immune defenses. We also suggest that DP1 is important in the Th1/Th2 balance of the immune response and in inflammatory reactions during infection.

To examine the function of prostaglandin (PG) D synthase (PGDS) gene, as well as endogenously produced PGD 2 in sleep regulation in vivo, we generated transgenic (TG) mice that overexpress human PGDS gene to study their sleep behavior. Although no difference was observed in the sleep͞wake patterns between wild-type and TG mice, a striking time-dependent increase in non-rapid eye movement (NREM), but not in rapid eye movement (REM), sleep was observed in two independent lines of TG mice after stimulation by tail clipping. Concomitantly, the spontaneous locomotor activity of TG animals was drastically decreased in response to the tail clip. Induction of NREM sleep in TG mice was positively correlated with the PGD2 production in the brain. Sleep, locomotion, and PGD2 content were essentially unchanged in wild-type mice after tail clipping. The results with TG mice demonstrate the involvement of the PGDS gene in the regulation of NREM sleep.

Hematopoietic prostaglandin (PG) D synthase (PGDS)is the first identified vertebrate ortholog in the Sigma class of the glutathione S-transferase (GST) family and catalyzes both isomerization of PGH 2 to PGD 2 and conjugation of glutathione to 1-chloro-2,4-dinitrobenzene. We introduced site-directed mutations of 199, which are presumed to participate in catalysis or PGH 2 substrate binding based on the crystallographic structure. Mutants were analyzed in terms of structure, GST and PGDS activities, and activation of the glutathione thiol group. Of all the mutants, only Y8F, W104I, K112E, and L199F showed minor but substantial differences in their far-UV circular dichroism spectra from the wild-type enzyme. Y8F, R14K/E, and W104I were completely inactive. C156L/Y selectively lost only PGDS activity. K112E reduced GST activity slightly and PGDS activity markedly, whereas K198E caused a selective decrease in PGDS activity and K m for glutathione and PGH 2 in the PGDS reaction. No significant changes were observed in the catalytic activities of Y152F and L199F, although their K m for glutathione was increased. Using 5,5-dithiobis(2-nitrobenzoic acid) as an SH-selective agent, we found that only Y8F and R14E/K did not accelerate the reactivity of the glutathione thiol group under the low reactivity condition of pH 5.0. Prostaglandin (PG)1 D synthase (PGDS) is the key enzyme responsible for the formation of PGD 2 and its additional metabolites, the J series of PGs; and these prostanoids exhibit a variety of pharmacological activities and are involved in a number of physiological processes (1). For example, PGD 2 induces vasodilation and bronchoconstriction (2, 3); inhibits platelet aggregation (4); regulates body temperature (5, 6), hormone release (7), and nociception (8); and promotes sleep (9). Furthermore, ⌬ 12 -PGJ 2 inhibits the growth of various tumor cell lines (10), and 15-deoxy-⌬ 12,14 -PGJ 2 is an endogenous ligand for a nuclear receptor, peroxisome proliferator-activated receptor ␥ (11, 12).Two distinct types of PGDS have been isolated and characterized biochemically and immunologically; one is GSHdependent or hematopoietic PGDS (13,14), and the other is GSH-independent or lipocalin-type PGDS (15). Hematopoietic PGDS expressed in antigen-presenting, Kupffer, dendritic, Langerhans (16), megakaryoblastic (17), and mast (18, 19) cells of various organs is involved in the production of PGD 2 as an allergic and inflammatory mediator. In addition, it was characterized as a member of the glutathione S-transferase (GST) gene family (20), whose members are known to catalyze the conjugation of GSH to an electrophilic substrate (21).Recently, we cloned the cDNA for rat hematopoietic PGDS, crystallized the recombinant enzyme, and determined by x-ray crystallography the three-dimensional structure of the enzyme complexed with GSH (22). The deduced amino acid sequence and the tertiary structure of hematopoietic PGDS classified the enzyme as a member of the Sigma class of GSTs. The enzyme isomerizes PGH 2 to PGD 2 sele...

Angiotensin II (Ang II) induces a prominent and sustained nitration and activation of ERK1/2 in rat vascular smooth muscle cells, both mediated via AT1 receptor. Nitration and activation was also shown for recombinant non-activated extracellular signal-regulated kinase (ERK) and MEK. Nitration and phosphorylation of ERK1/2 by Ang II was significantly inhibited by NAD(P)H inhibitors and scavengers of oxygen and nitrogen reactive species and completely blocked by a selective inducible nitric-oxide synthase inhibitor. MEK inhibitor U0126 did not affect ERK nitration but completely blocked activation. These data indicate that Ang II nitrates and activates ERK1/2 via a reactive species-sensitive pathway.

No abstract