Spleen Of Old Rats Research Articles

Anti-tumor effect of l-deprenyl is associated with enhanced central and peripheral neurotransmission and immune reactivity in rats with carcinogen-induced mammary tumors

l-Deprenyl, a monoamine oxidase-B (MAO-B) inhibitor, has previously been shown to improve immune responses and restore noradrenergic (NA) nerve fibers in the spleen of old rats. In tumor-bearing rats, l-deprenyl inhibited tumor incidence and enhanced tuberoinfundibular dopaminergic (TIDA) neurotransmission in the hypothalamus. The aim of the present study was to investigate whether alterations in sympathetic NA activity and cellular immune responses in the spleen, and TIDA activity in the hypothalamus, accompany deprenyl-induced regression of 9,10-dimethyl-1,2-benzanthracene (DMBA)-induced mammary tumors. Rats with DMBA-induced mammary tumors were treated with 0, 2.5 mg, or 5.0 mg/kg body weight of deprenyl daily for 13 weeks. Saline-treated tumor-bearing rats exhibited reduced splenic IL-2 and IFN-γ levels, and lowered splenic norepinephrine (NE) concentration and hypothalamic dopaminergic activity, compared to rats without tumors. In contrast, treatment with 2.5 mg/kg and 5.0 mg/kg of deprenyl reduced the number and size of mammary tumors. Deprenyl-induced tumor regression was accompanied by increased immune measures in the spleen, including enhanced IL-2 and IFN-γ production, and NK cell activity. Neural measures enhanced by deprenyl included NE concentration in the spleen and TIDA neuronal activity in the hypothalamus. These results suggest that (1) mammary tumorigenesis is associated with the inhibition of sympathetic NA activity in the spleen, TIDA activity in the hypothalamus, and cell-mediated immunity, and (2) reversal of the inhibition of catecholaminergic neuronal activities of the central nervous system and peripheral nervous system by deprenyl may enhance anti-tumor immunity.

Restoration of splenic noradrenergic nerve fibers and immune reactivity in old F344 rats: a comparison between L-deprenyl and L-desmethyldeprenyl

L-deprenyl, a monoamine oxidase-B inhibitor, partially reversed the age-associated decline in splenic sympathetic noradrenergic (NA) innervation and immune reactivity in old male rats. The purpose of the present study was to examine whether the effects of deprenyl on splenic sympathetic NA nerve fibers and immune functions are mediated through a metabolite of deprenyl, L-desmethyldeprenyl. Old male F344 rats were treated with 0, 0.25, or 1.0 mg L-(−)-deprenyl/kg BW; 0.025, 0.25, or 1.0 mg L-(−)-desmethyldeprenyl/kg BW; and 1.0 mg D-(+)-desmethyldeprenyl/kg BW i.p. daily for 8 weeks. The animals were sacrificed after a 10-day drug wash-out period and the spleens were removed for histofluorescence, immunocytochemistry, neurochemical, and immunological analysis. The volume density of NA nerve fibers was increased in the spleens of deprenyl- and L-desmethyldeprenyl-treated old rats. Con A-induced IFN-γ production by spleen cells was elevated in 1.0 mg/kg deprenyl- and L-desmethyldeprenyl-treated rats in comparison to saline- and D-desmethyldeprenyl-treated old rats. Deprenyl and desmethyldeprenyl treatment did not alter the percentage of CD5+ T cells, but treatment with 1.0 mg/kg deprenyl and 0.025 mg/kg L-desmethyldeprenyl prevented the decline in the percentage of sIgM +B cells in the spleens of old rats. These results suggest that L-desmethyldeprenyl may be as equipotent as deprenyl in preventing age-associated diminution in splenic sympathetic NA innervation and immunocompetence.

L-deprenyl-induced increase in IL-2 and NK cell activity accompanies restoration of noradrenergic nerve fibers in the spleens of old F344 rats

Previously, we have hypothesized a causal relationship between some measures of immunosenescence and the age-related decline in sympathetic noradrenergic (NA) nerve fibers in spleen and lymph nodes of F344 rats. In the present study, we investigated this interrelationship further by measuring NK cell activity, Con A-induced IL-2 production, norepinephrine (NE) concentration, and morphological localization of NA and neuropeptide-Y (NPY) nerve fibers in the spleens of old (21 months old) male F344 rats after 10 weeks of daily treatment with low doses of l-deprenyl, an irreversible monoamine oxidase-B inhibitor, followed by a 9-day wash-out period. NK cell activity and Con A-induced IL-2 production were increased in deprenyl-treated old rats in comparison to untreated and saline-treated old rats. Deprenyl treatment did not alter the percentage of CD5+ T-cells, but moderately increased the percentage of sIgM + B-cells in the spleens of old rats. In addition to changes in immune responses, NE content and the volume density of NA and NPY nerve fibers were partially augmented in the spleens of deprenyl-treated old rats. In a separate study, various concentrations of deprenyl were added in vitro to spleen cells from young and old F344 rats to examine the direct effects of the drug on Con A-induced IL-2 production. In contrast to in vivo treatment, in vitro addition of deprenyl did not alter the Con A-induced IL-2 production by splenocytes from old rats. Together, these results suggest that the ability of deprenyl to enhance certain immune responses are interlinked to the restoration of sympathetic NA and NPY nerve fibers in the spleens of old rats.

Restoration of sympathetic noradrenergic nerve fibers in the spleen by low doses of l-deprenyl treatment in young sympathectomized and old Fischer 344 rats

It is well-established that noradrenergic (NA) nerve fibers in spleen and lymph nodes influence cell-mediated immune responses. Such responses are diminished in young animals following chemical sympathectomy and in older animals accompanying an age-related decline in NA nerve fibers in spleen and lymph nodes. The purpose of this study was to determine whether treatment with deprenyl, an irreversible monoamine oxidase-B (MAO-B) inhibitor, would hasten the process of splenic NA reinnervation following chemical sympathectomy in young rats and would reverse the age-related loss of sympathetic NA fibers in the spleen of old rats. To examine the effects of deprenyl in young sympathectomized rats, 3-month-old male Fischer 344 (F344) rats were treated with 6-hydroxydopamine (6-OHDA) and administered 0, 0.25, 1.0, 2.5, or 5.0 mg deprenyl/kg body weight (BW)/day intraperitoneally (i.p.) for 1, 15, or 30 days. In another study, 21-month-old male F344 rats were treated with 0, 0.25, or 1.0 mg deprenyl/kg BW/day i.p. for 9 weeks. At the end of the treatment period, spleens were removed and NA innervation was assessed by fluorescence histochemistry, immunocytochemistry, and quantitation of norepinephrine (NE) by high performance liquid chromatography with electrochemical detection (HPLC-EC). In the spleens of young sympathectomized rats, there was faint fluorescence or absence of fluorescence and tyrosine hydroxylase-positive (TH+) fibers around the central arteriole and in the periarteriolar lymphatic sheath of the white pulp one day after administration of 6-OHDA, indicating a severe loss of NA innervation compared with unlesioned control animals. Treatment of sympathectomized rats with 1.0 mg, 2.5 mg, and 5.0 mg/kg deprenyl for 30 days increased the density of NA innervation estimated by both fluorescence histochemistry and immunocytochemistry compared with vehicle-treated controls recovering spontaneously from 6-OHDA. Splenic NE concentration was increased in the hilar region of sympathectomized rats treated with 2.5 mg and 1.0 mg/kg deprenyl after 15 and 30 days, respectively, compared with untreated and vehicle-treated sympathectomized rats. The spleens of untreated and saline-treated old rats showed a reduction in the density of NA innervation in the white pulp compared with young animals. Treatment of old rats for 9 weeks with 1.0 mg/kg deprenyl induced moderate to intense fluorescent fibers and linear TH+ nerve fibers around the central arteriole and in other compartments of the white pulp, and increased splenic NE concentration in the hilar region and NE content in the whole spleen. Taken together, these results provide strong evidence for a neurorestorative property of deprenyl on sympathetic NA innervation of the spleen, which may lead to an improvement in cell-mediated immune responses.

The effects of in vivo administration of active lipids (AL-721) on natural killer cell activity and mitogen responsiveness in old rats

The cytotoxic activity of natural killer (NK) cells under both basal and interferon (IFN)-induced conditions, as well as the proliferative response of lymphocytes to ConA in old rats treated in vivo with AL-721 have been analyzed. The low levels of basal NK cell activity present in spleen of old rats were completely recovered to the levels of NK cytotoxicity obtained in young rats in animals treated in vivo with AL-721. Similar results were obtained for in vitro IFN-boosting of NK cells, in so far as the reduced IFN-responsiveness of NK cells from old untreated rats was restored to the levels of IFN-induced young NK activity in animals treated in vivo with AL-721. The evaluation of the proliferative response of lymphocytes to ConA revealed that old rats treated in vivo with AL-721 showed an increased proliferative capacity in comparison to old untreated animals even if the mitogenic response was not recovered up to the levels observed in young rats.

Aminoacylation and methylation of tRNA as a function of age in the rat

Aminoacylation of tRNA was compared between preparations from spleen obtained from young (age: 2–3 months) and old (age: 9–12 months) rats. Assays with ten amino acids indicated no large differences in initial rate or total incorporation between the amino-acylating synthetases from spleens of the two age groups when each was assayed with tRNA from the same or different age group. On the other hand, tRNA from spleens of old rats accepted only 50 per cent or less of the amount of amino acid that tRNA from spleens of young animals accepted, with the exception of arginine. tRNA from spleens or livers of old rats was methylated in vivo to a lesser degree than that from young animals. Reversed phase chromatography of tRNA from spleens methylated in vivo indicated both quantitatively less and qualitatively different patterns for material of old animals compared to young. Such analysis of tRNA from liver showed the quantitative difference but no qualitative change. The decreased amount of methylation in liver was not due to the loss of certain methylated nucleotides but rather to a decrease in all methylated components. In vitro assays of methylase activity showed no significant difference between the two age groups although there was more activity in spleen preparations than in liver. Thus, senescence in rats is reflected in certain qualitative and/or quantitative differences in tRNA metabolism depending on the organ examined.