Differences in luteinizing hormone release stimulated in rat anterior pituitary cells by leukotriene C4 and by gonadotropin-releasing hormone in vitro

Transcellular biosynthesis of cysteinyl leukotrienes in rat neuronal and glial cells

Leukotrienes are mediators of inflammation that belong to a family of lipids derived from arachidonic acid by the action of 5-lipoxygenase. Leukotrienes have been detected in the central nervous system in association with different pathological events, but little is known about their biosynthesis or function in the brain. When rat neurons and glial cells in primary culture were stimulated with the calcium ionophore, no significant biosynthesis of leukotrienes was detected using liquid chromatography/mass spectrometry (LC/MS) techniques. However, when exogenous LTA(4) was added to these cultured cells, both neurons and glia were able to synthesize LTC(4). Activated neutrophils are known to supply LTA(4) to other cells for transcellular biosynthesis of cysteinyl-leukotrienes. Since neutrophils can infiltrate brain tissue after stroke or traumatic brain injury, we examined whether neutrophils play a similar role in the central nervous system. When peripheral blood neutrophils were co-cultured with rat neurons, glia cells, and then stimulated with calcium ionophore, a robust production of LTC(4), LTD(4), and LTE(4) was observed, revealing that neurons and glia can participate in the transcellular mechanism of leukotriene biosynthesis. The formation of LTC(4) through this mechanism may be relevant in the genesis and progression of the inflammatory response as a result of brain injury.

Expression of microsomal glutathione S-transferase type 3 mRNA in the rat nervous system

Microsomal glutathione S-transferase type 3 (MGST3) is a recently identified member of a large superfamily of enzymes involved in biotransformation of xenobiotics and biosynthesis of eicosanoids, including prostaglandins and leukotrienes. Using in situ hybridization histochemistry and reverse transcription polymerase chain reaction, we characterized the expression of MGST3 mRNA in the rat nervous system based on the cloned rat MGST3 gene, under normal conditions and after systemic administration of lipopolysaccharide (LPS). The MGST3 mRNA seemed to be confined to neurons. The broad distribution in the brain was characterized by a strong signal in the hippocampal formation and in the nuclei of the cranial nerves. A moderate signal was found in the cortex, thalamus, amygdala and substantia nigra and a weak signal in the hypothalamus. Motoneurons in the spinal cord and sensory neurons in dorsal root ganglia displayed strong MGST3 mRNA signal. No significant changes in the level of expression of MGST3 mRNA in the brain were found 1, 3 or 6 h after LPS administration. The pattern of distribution of MGST3 mRNA in the rat nervous system and the lack of response to LPS do not support a role for MGST3 in the biosynthesis of proinflammatory eicosanoids but rather suggest other functions, perhaps in metabolic detoxication and neuroprotection.

Role of leukotriene C4 in follicle-stimulating hormone (FSH) secretion in female rat pituitary

Leukotriene C4, at doses of 0.01 and 0.1 nmol/l added to superfused cells in pulse of 4-min duration, evoked follicle-stimulating hormone (FSH) release up to 12- to 26-fold of basal secretion. Higher and lower concentrations of leukotriene C4 were not able to induce FSH secretion. Gonadotropin-releasing hormone (GnRH)-induced FSH release was reduced by 38-57% by the leukotriene receptor antagonist FPL 55712 (10 mumol/l). Moreover, we have shown that FSH release occurs parallel to leukotriene C4 synthesis in rat anterior pituitary cells. Mellitin (100 nmol/l), an activator of phospholipase A2, induced FSH and radioactivity secretion in rat anterior pituitary cells previously preincubated for 24 h with [3H]arachidonic acid (AA).