Immunological changes produced in rats by prenatal exposure to carbon monoxide

Cypermethrin-induced alteration of thymocyte distribution and functions in prenatally-exposed rats

The synthetic pyrethroid insecticide, cypermethrin (50 mg/kg) was given during gestation to pregnant rats by gavage in corn oil. Prenatal cypermethrin exposure induced a significant decrease in the absolute number of all thymocyte subsets during the first 30 days after birth, being the double negative CD4-CD8-, single positive CD4 and CD8 T cells preferentially affected. Later on day 60 and 90 double positive CD4+CD8+ and single positive thymocytes gradually recovered, while the total number of CD4 CD8 cells was increased. Moreover, thymocytes from rats prenatally exposed to cypermethrin showed an impaired ability to proliferate in response to different doses of Concanavalin A (ConA) and human recombinant interleukin-2 (hrIL-2) and to produce and/or release IL-2. Overall, our results indicate that cypermethrin administered during prenatal period can affect multiple steps in thymocyte differentiation pathways resulting in an altered cell subset distribution and an impairment of thymocyte functions.

Pathogenicity of carbon monoxide

The effects of carbon monoxide, one of the most commonly encountered toxic agents in forensic practice, have been known for a long time, but the nature of its bonding to the heme prosthetic group of hemoproteins has only recently been elucidated. In addition to reducing the oxygen capacity of the blood and the consequent systemic hypoxia, carbon monoxide interferes with the dissociation of oxyhemoglobin and the removal of carbon dioxide. Carbon monoxide also produces a direct cytotoxic effect by inactivating some intracellular respiratory enzymes, but the relative importance of these various mechanisms often remains uncertain, particularly with regard to the lesions in the brain and myocardium.

Pro-opiomelanocortin gene expression and protein processing in rat mononuclear leukocytes

Although production of pro-opiomelanocortin (POMC) mRNA and POMC-derived peptides in extrapituitary tissues, including immune tissues, has been demonstrated, questions remain concerning the nature of POMC transcripts and peptide products. With regard to POMC gene expression in lymphocytes, the expression of full-length mRNA and POMC has been questioned. In the present report, we have tested for the existence of these molecules. Western blot analysis with an antibody against POMC-derived adrenocorticotropic hormone (ACTH) specifically identified identical immunoreactive (ir) species in both rat anterior pituitary (AP) and splenocyte cell extracts. The relative molecular weights were those expected for nonglycosylated ACTH, as well as its biosynthetic intermediate, and POMC. Mitogen stimulation of splenic mononuclear cells (MNC) enhanced the levels of these three molecular species. Primer extension analysis identified a band which migrated with a size equivalent to a full-length POMC transcript (approximately 816 nt) in both mitogen-stimulated MNC and AP mRNA. Macrophages produced POMC protein and mRNA among unstimulated splenocytes, while lymphocytes could be induced to produce POMC mRNA upon stimulation. 5' RACE-tailed PCR products were cloned and sequenced. A mRNA encoding all three POMC exons was identified in Concanavalin A (ConA)-stimulated MNC and was identical to that from the anterior pituitary. These results unequivocally demonstrate that mononuclear cells produce full-length POMC transcripts. Its regulation in lymphocytes is distinct from that in macrophages which constitutively produce POMC-derived peptides and mRNA. Also, the biosynthetic pathway of ACTH from POMC in splenic MNC stimulated with ConA appears to be identical to that in rat corticotrophs.

Prenatal exposure to carbon monoxide and vascular responsiveness of rat resistance vessels

The aim of the present study was to investigate the influence of prenatal exposure to carbon monoxide (CO) on vascular reactivity of rat resistance vessels, in different stages of neurogenesis. Both prenatally CO-exposed and control male Wistar pups (5-7, 9-11, 14-16, 20-22 days) were tested vs respective 60 day adult rats. The results showed that: (i) at 5-7 days of age, TTX caused a more marked inhibition of perivascular nerve stimulation (PNS)-evoked vasoconstriction in CO-exposed animals with respect to controls; (ii) the NO-related relaxant effect by ACh in CO-exposed group appeared earlier (5-7 days) than in control group (9-11 days); (iii) the contractile response evoked by ACh on resting tone disappeared earlier (after 14-16 days) than in control group (after 20-22 days). These observations suggested that CO-exposure might induce changes in nerve electrophysiological properties and might cause a precocious maturation of the NO-related enzymatic mechanism implicated in ACh-relaxation.

The kinetics of ACTH expression in rat leukocyte subpopulations

The pro-opiomelanocortin (POMC) gene encodes a family of peptides originally identified in the pituitary gland. An important POMC-derived peptide hormone, corticotropin (ACTH), is also produced by leukocytes and modulates in vitro immune functions. The present investigation was undertaken to determine the kinetics and cellular distribution of ACTH immunoreactivity (ACTH-ir) in vitro in rat splenic leukocyte subpopulations. Cells were cultured with Concanavalin A (ConA), lipopolysaccharide (LPS), or media alone. ACTH-ir was identified with a specific antiserum raised against ACTH 1-24. Double indirect-immunofluorescence was done at 0, 21, and 48 h for B, t-helper (Th), and T-cytotoxic (CTL) cells. Initial kinetic studies demonstrated peak ACTH-ir in all cell types at 18-21 h for both ConA and LPS treatments. A few leukocytes (1-2%) expressed ACTH-ir at 0 h and these were found to be macrophages (MO). Lymphocyte ACTH-ir is 0% at 0 h and rises to 90 +/- 5% and 75 +/- 6% at 21 h with ConA and LPS, respectively. This sharply contrasts with 9 +/- 4% of each cell type positive in media alone at 21 h. The percent immunoreactivity among the three lymphocyte subpopulations did not significantly differ at any single treatment at a single time point. However, there were significant differences in the intensity levels among the subpopulations. At 48 h of ConA or LPS treatment only 10 +/- 4% of B, Th and Tc were positive, while none were positive in media alone. Stimulated peritoneal MO also increase positivity for ACTH-ir (85 +/- 5%). These results indicate that rat splenic B, CTL, and Th lymphocytes can be immunologically stimulated to express the peptide hormone ACTH and that basal ACTH expression in macrophages is distinct from that in lymphocytes. Thus, lymphocyte-derived ACTH may be a paracrine or autocrine regulator of immune function.

Irreversible impairment of active avoidance behavior in rats prenatally exposed to mild concentrations of carbon monoxide

Wistar female rats were exposed to relatively mild concentrations of carbon monoxide (75 and 150 ppm) from day 0 to day 20 of pregnancy. The results show that prenatal exposure to CO (150 ppm) significantly impairs the acquisition of a two-way active avoidance task in 3-month-old male rats as well as the acquisition and reacquisition of this schedule in 18-month-old animals subjected to six daily 20-trial sessions. These deficits do not seem to be attributable to alterations of a non-associative nature, as the intertrial activity and the escape response latencies in CO exposed animals were not significantly affected with respect to controls. These findings, showing that gestational exposure to CO induces in rat offspring permanent learning and memory impairment, confirm that the offspring of smoking mothers may be at considerably greater risk than current epidemiological studies on birthweight and neonatal mortality suggest.