Robert B. Zurier

Oxidative metabolism of anandamide

In addition to the well studied hydrolytic metabolism of anandamide, a number of oxidative processes are also possible. Several routes somewhat analogous to the metabolism of free arachidonic acid have been reported. These involve mediation by various lipoxygenases and COX-2 and lead to ethanolamide analogs of the prostaglandins and HETES. The physiological significance of these products is not well understood at this time. There are also preliminary data suggesting a pathway involving oxidation of the hydroxy group of anandamide to a putative metabolite, N-arachidonyl glycine (AA-gly). This molecule displays activities in experimental models that suggest that it may play a role in some of the activities attributed to its precursor, anandamide.

Suppression of interleukin 2-dependent human T cell growth in vitro by prostaglandin E (PGE) and their precursor fatty acids. Evidence for a PGE-independent mechanism of inhibition by the fatty acids.

PGE represent oxygenation products of polyunsaturated essential fatty acids and are important regulators of cell-mediated immune responses. Because oils enriched in such fatty acids reduce inflammation and tissue injury in vivo, we examined the effects of these PGE precursors on IL-2-driven growth of human T lymphocytes. Dihomogamma linoleic acid (DGLA), AA, and their metabolites (PGE1 and PGE2, respectively) strongly inhibited short- and long-term growth of IL-2-dependent T cell cultures; EPA was much less inhibitory and its product, PGE3, failed to suppress IL-2 responses. Short-term pretreatment of the cells with DGLA or AA and removal of the fatty acids before the proliferation assay resulted in a smaller reduction in [3H]TdR incorporation. PGE and fatty acids did not alter the number of high affinity IL-2 binding sites on the T cell cultures but reduced the percentage of cells expressing CD25 and HLA class II molecules. No PGE was detected in supernatants from the fatty acid-treated cultures. Moreover, indomethacin, a cyclooxygenase inhibitor, did not reverse the antiproliferative effects of the fatty acids. Together, these findings indicate that fatty acids can inhibit IL-2-driven T cell growth via a PGE-independent mechanism and might be relevant to inflammatory diseases associated with persistent T cell activation.

Restricted heterogeneity of T cell receptor transcripts in rheumatoid synovium.

RA is characterized by massive proliferation of synovial tissue, accompanying infiltration of the tissue with CD4+ T lymphocytes, and a genetic linkage to the MHC antigen HLA-DR4. Since T cells are restricted by class II MHC molecules such as DR4, this suggests a direct role for these CD4+ cells in pathogenesis. To investigate T cell receptor (TCR) usage in RA, we used oligonucleotide primers specific for each of the major alpha and beta TCR subfamilies to amplify cDNA derived from whole synovium or synovial tissue T cell lines in a family-specific manner. Detection of amplified DNA was facilitated by utilizing oligonucleotide probes derived from the constant regions of the TCRs. The TCR repertoire present in the synovial T cell lines was quite heterogeneous, with an average of 15 alpha chains and 15.8 beta chains detected. When synovial tissue was analyzed, the predominant TCR subfamilies detected tended to be more restricted, with an average of 4.6 alpha chains and 8.6 beta chains detected. This compared with an average of six alpha chains and 12 beta chains in nonrheumatoid synovial samples. The average percentage of synovia positive per TCR beta family was significantly lower for RA versus non-RA specimens (46.1 vs 65.6%, P = 0.034). These findings indicate that while a polyclonal population of T cells is present in RA synovium, the predominant patterns of TCR transcript expression may be somewhat more restricted, suggesting that TCR-based therapy of RA is possible.

Suppression of immune complex vasculitis in rats by prostaglandin.

Immune complex-induced vascular damage can be markedly suppressed by treatment of rats with either prostaglandin (PG)E1 or its stable derivative, 15-(S)-15-methyl PGE1, but not with PGF2 alpha. In addition, PGD2 and PGE2 also show suppressive effects. The PGE1 derivative is considerably more effective than PGE1 and shows potent anti-inflammatory activity even after oral administration. Suppression of the vasculitis reaction is reflected by a greatly diminished increase in vasopermeability, indicating little or no vascular damage. In suppressed animals, the infiltration of neutrophils is greatly reduced, and those leukocytes that have appeared at tissue sites fail to show phagocytic uptake of immune complexes. In suppressed animals, the skin sites nevertheless show deposits of immune complexes and C3 fixation in vascular walls. Neutrophils harvested from the blood of rats treated with PGE1 show depressed responsiveness in chemotaxis and in enzyme secretion after incubation with chemotactic peptide. These studies indicate that certain PG have potent anti-inflammatory activity, which may be related to their effects on leukocytes.

Release of prostaglandins from human polymorphonuclear leukocytes

Human PMNs release prostaglandins E and F to the surrounding medium when these cells are exposed to zymosan. PGE1 is the prostaglandin compound found in highest concentration in the medium, and the PGE/PGF balance is approximately 3∶1. Release of prostaglandins is not due to platelet contamination. Agents which inhibit prostaglandin synthesis (indomethacin, aspirin) prevent release of prostaglandins from phagocytic cells. Addition to cells of dibutyryl cyclic 3′,5′-adenosine monophosphate produces striking increases in concentrations of prostaglandins released during ingestion of zymosan. Prostaglandins appear to be synthesized by human PMN during phagocytosis, and their release from cells may help regulate the inflammatory response.

Fatty acids, inflammation and immune responses

Evidence obtained from experiments in vitro and in vivo suggests that certain unsaturated fatty acids (FA) may be safe and effective antiinflammatory and immunomodulatory agents. Generation of a unique eicosanoid profile with different biological effects by administration of FA precursors other than arachidonic acid is one approach under investigation. In addition to their role as eicosanoid precursors, FA are of major importance in maintaining cell membrane structure, are key determinants of membrane bound enzyme activity and receptor expression. FA can exert these functions directly and therefore may themselves be important regulators of immune responses. For example, certain FA influence cytokine production and proliferation of human T lymphocytes in a manner that is direct and not due to their conversion to eicosanoids. The observations indicate that FA can modulate immune responses by acting directly on T-cells and suggest that alteration of cellular FA may be a worthwhile approach to control of inflammation.

CD4+CD25high T cell numbers are enriched in the peripheral blood of patients with rheumatoid arthritis

Accumulating evidences support that CD4(+)CD25(high) T regulatory (Treg) cells play an essential role in controlling and preventing autoimmunity. Paradoxically, RA patients have elevated numbers of circulating CD4(+)CD25(high) T cells, however, the inflammation is still ongoing. Further identification of these CD4(+)CD25(high) T cells may contribute to a better understanding of underlying mechanisms. We show here that these CD4(+)CD25(high) T cells were composed of CD4(+)CD25(high)FoxP3(+) Treg cells and activated CD4(+)CD25(high)FoxP3(-) effector cells. Moreover, there were significantly more Treg cells and effector T cells expressing GITR, and more monocytes expressing GITR-L. Thus, although RA patients have elevated numbers of CD4(+)CD25(high) T cells, the suppressive function is not increased, because of the increased number of activated effector T cells. In addition, the GITR-GITR-L system was activated in RA patients, which might lead to diminish suppressive activity of Treg cells and/or lead to resistance of activated effector T cells to suppression by Treg cells, thus, contributing to the ongoing inflammation in RA patients.

Dimethylheptyl‐THC‐11 OIC acid: A nonpsychoactive antiinflammatory agent with a cannabinoid template structure

OBJECTIVE To assess the antiinflammatory activity of dimethylheptyl-THC-11 oic acid (DMH-11C), a nonpsychoactive synthetic derivative of tetrahydrocannabinol. METHODS Acute inflammation was induced by injection of interleukin-1beta and tumor necrosis factor alpha into subcutaneous air pouches formed on the backs of mice. Inflammation was quantified 6 hours later by pouch fluid leukocyte counts. Adjuvant-induced polyarthritis in rats was used as a model of chronic inflammation and joint tissue injury. Animals were either untreated, treated with safflower oil, or treated with DMH-11C in safflower oil. Arthritis was assessed by clinical observation and by histomorphologic evaluation of tibiotarsal joints. RESULTS Oral administration of DMH-11C reduced the accumulation of pouch fluid leukocytes and significantly reduced the severity of adjuvant-induced polyarthritis. Histopathologic studies of tibiotarsal joints showed that DMH-11C treatment attenuated pannus formation and joint tissue injury. CONCLUSION DMH-11C suppresses acute inflammation in the subcutaneous air pouch in mice and chronic joint inflammation characteristic of adjuvant disease in rats. These results demonstrate the potential use of this nonpsychoactive cannabinoid as an antiinflammatory agent.

Use of Medium-Chain Triglyceride in Management of Patients with Massive Resection of the Small Intestine

ALTHOUGH the consequences of extensive resection of the small intestine differ in pattern and intensity a syndrome of conditioned malnutrition invariably follows.1 2 3 4 5 The chief manifestation i...

Regulation of anandamide tissue levels by N-arachidonylglycine

N-arachidonylglycine (NAGly), the carboxylic analog of the endocannabinoid anandamide, occurs in rat and bovine brain as well as in peripheral sites and shows activity against tonic, formalin-induced pain. It was also observed, using cell membrane preparations, that it inhibits the hydrolytic activity of fatty acid amide hydrolase (FAAH) on anandamide (N-arachidonylethanolamide). These data suggested that it may serve as an endogenous regulator of tissue anandamide concentrations. In this report, we show findings derived from mass spectrometric analyses, indicating that blood levels of anandamide in rats given 10 mg/kg p.o. of NAGly were increased significantly by more than 9-fold when compared with vehicle-treated controls. In vitro evidence in RAW 264.7 cells using a deuterium-labeled NAGly demonstrated that it was not a precursor or source of arachidonic acid for the observed 50% rise in anandamide levels, suggesting that the increase was due to some effect other than increased biosynthesis of anandamide. Moreover, the findings presented here suggest that NAGly can serve as a model for the design of agents to provide pharmacological control of tissue anandamide concentrations.