Proliferation Of Thymic Lymphocytes Research Articles

The signal pathway of melatonin mediates the monochromatic light-induced T-lymphocyte apoptosis in chicken thymus

Our previous study revealed that under monochromatic red light (RL), the melatonin nuclear receptor reduces the proliferation activity of broiler thymic lymphocytes through the P65 signaling pathway. The main objective of this study was to investigate the signal mechanism by which RL decreases thymic lymphocyte proliferation. Initially, broilers were purchased and randomly assigned to be fed under white light (WL), red light (RL), green light (GL), and blue light (BL). Pinealectomy was performed 3 d later, and the broilers were euthanized after 14 d. The results showed that the expression of the antiapoptotic proteins Bcl-2/Bcl-xl decreased under RL, while the expression of the pro-apoptotic factor Bax/caspase-3 and the pro-inflammatory factors INF-γ/TNF-α/IL-6 increased. After pinealectomy, the expression of Bax/TNF-α/IL-6 increased in conjunction with the decrease in Bcl-2 expression. In vitro experiments demonstrated that exogenous melatonin decreased the expression of Bax/TNF-α/IL-6 in thymic lymphocytes of chicks reared under RL. This melatonin-induced effect was enhanced by SR1078 (RORα/RORγ agonist) but attenuated by SR3335 (RORα antagonist) and BAY (P65 antagonist). These findings revealed that the melatonin nuclear receptor RORα/RORγ promotes the expression of the pro-apoptotic factor Bax/caspase-3 and the pro-inflammatory factors INF-γ/TNF-α/IL-6, while inhibiting the expression of the antiapoptotic factor Bcl-2/Bcl-xl. Our research suggested the signaling pathway of monochromatic red light impacts the apoptosis of thymus lymphocytes in broiler.

Organ-specific effects on glycolysis by the dioxin-activated aryl hydrocarbon receptor.

Activation of the aryl hydrocarbon receptor (AHR) by the environmental toxin dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD) causes diverse toxicities, including thymus atrophy and hepatosteatosis. The mechanisms by which AHR activation by TCDD leads to these toxicities are not fully understood. Here we studied the effects of TCDD on a major energy pathway, glycolysis, using the chick embryo close to hatching, a well-established model for studying dioxin toxicity. We showed that 24 hr of TCDD treatment causes changes in glycolysis in both thymus and liver. In thymus glands, TCDD decreased mRNAs for glycolytic genes and glucose transporters, glycolytic indices and levels of IL7 mRNA, phosphorylated AKT (pAKT) and HIF1A, stimulators of glycolysis and promoters of survival and proliferation of thymic lymphocytes. In contrast, in liver, TCDD increased mRNA levels for glycolytic genes and glucose transporters, glycolytic endpoints and pAKT levels. Similarly, increases by TCDD in mRNA levels for glycolytic genes and glucose transporters in human primary hepatocytes showed that effects in chick embryo liver pertain also to human cells. Treatment with the glycolytic inhibitor 2-deoxy-d-glucose exacerbated the effects on thymus atrophy by TCDD, supporting a role for decreased glycolysis in thymus atrophy by TCDD, but did not prevent hepatosteatosis. NAD+ precursors abolished TCDD effects on glycolytic endpoints in both thymus and liver. In summary, we report here that dioxin disrupts glycolysis mediated energy metabolism in both thymus and liver, and that it does so in opposite ways, decreasing it in the thymus and increasing it in the liver. Further, the findings support NAD+ boosting as a strategy against metabolic effects of environmental pollutants such as dioxins.

Changes in apoptosis, proliferation and T lymphocyte subtype on thymic cells of SPF chickens infected with reticuloendotheliosis virus

Reticuloendotheliosis virus (REV), an avian retrovirus is able to infect a variety of birds and can cause immunosuppression. The aim of this study was to investigate the relationship of thymic lymphocytes apoptosis, proliferation and T cell subtype with immunosuppression. In this study, a hundred and twenty one-day old SPF chickens were randomly divided into control groups (group C) and a REV infection groups (group I). The chickens of group I received intraperitoneal injections of REV with 104.62/0.1 ml TCID50. On day 14, 21, 28 and 35 post-inoculation, the chickens of C group and I group were sacrificed by cardiac puncture blood collection, and the thymic lymphocytes was sterile collected. The proliferation ability of lymphocytes was tested by Cell Counting Kit-8. Flow cytometry was performed to detect apoptosis, cell cycle stage and the change in T cell subtype. The RNA genome copy numbers of REV virus were detected using real-time PCR. Real-time PCR and western blotting were performed to analyze the expression of CyclinD1 and Bcl-2. Our results showed that REV genome copy number steadily declined, the proliferation potential of thymic lymphocytes was inhibited, lymphocytes apoptosed, the ratio of CD4+/CD8+ decreased and the expression of CyclinD1 and Bcl-2 were firstly inhibited, then rapidly recovered. Thus, immunosuppression lead by REV is closely related to the change of T cell subtype, apoptosis, and proliferation of thymic lymphocytes.

ChemInform Abstract: Synthesis and Mitogenic Activity of New Imidazo(2,1-b)thiazoles

Eight new imidazo[2,1-b]thiazoles were synthesized in order to evaluate their ability to stimulate the proliferation of thymic lymphocytes. The 2-chloro (5–8) proved more active than the 2,3-dimethyl derivatives (1–4): in particular compounds 6 and 7 were more active than levamisole.

Differential effects of synthetic indoloquinolizines on in vitro rat lymphocyte and macrophage functions

Indoloquinolizines are natural alkaloid indole products grouped as β-carbolines. These compounds are commonly associated with neurological activities, but little is known about their role as immunomodulating agents. The present study was undertaken to evaluate the effects of synthetic indoloquinolizines on in vitro parameters of rat lymphocyte and macrophage functions. It was observed that proliferation of thymic lymphocytes was significantly ( p<0.05) increased (20–30% increase) by dihydro-indoloquinolizinium chloride ( 2), dihydro-indoloquinolizinyl-ethanone ( 3), and dimeric dihydro-indoloquinolizinium dichloride ( 6), whereas dimeric indoloquinolizine ( 7) caused up to 40% increase in lymphoproliferation at concentrations ranging from 10 −11 to 10 −5 M, compared with untreated control. In contrast, indoloquinolizinium chloride ( 4) and indoloquinolizine ( 5) were toxic for lymphocytes at concentrations from 10 −9 to 10 −5 M, and compounds 6 and 7 were toxic at 10 −5 M. In addition, nitric oxide production by LPS-treated peritoneal macrophages was significantly ( p<0.05) increased (up to 30% increase) by compounds 4 and 5 at concentrations of 10 −11 to 10 −5 M, and 10 −5 M, respectively; however, compounds 6 and 7 were toxic for macrophages at all concentrations tested. Furthermore, TNF-α production was also significantly increased ( p<0.01) by compounds 4 and 5 (up to 30-fold increase) compared with untreated control. These novel synthetic indoloquinolizines could serve as immunotherapeutic agents by selectively increasing the pool of activated T lymphocytes or stimulating macrophage functions, with potential use in the treatment of infectious diseases including AIDS and cancer.

The immunosuppressive effects of chronic morphine treatment are partially dependent on corticosterone and mediated by the μ-opioid receptor

Wild-type and mu-opioid receptor knockout (MORKO) mice were used to investigate the role of corticosterone (CORT) and the mu-opioid receptor (MOR) in chronic morphine-mediated immunosuppression. We found that although plasma CORT concentrations in CORT infusion (10 mg/kg/day) and morphine-pellet implantation (75 mg) mice were similar (400-450 ng/ml), chronic morphine treatment resulted in a significantly higher (two- to threefold) inhibition of thymic, splenic, and lymph node cellularity; inhibition of thymic-lymphocyte proliferation; inhibition of IL-2 synthesis; and activation of macrophage nitric oxide (NO) production when compared with CORT infusion. In addition, results show that the inhibition of IFN-gamma synthesis and splenic- and lymph node-lymphocyte proliferation and activation of macrophage TNF-alpha and IL-1beta synthesis occurred only with chronic morphine treatment but not with CORT infusion. These morphine effects were abolished in MORKO mice. The role of the sympathetic nervous system on morphine-mediated effects was investigated by using the ganglionic blocker chlorisondamine. Our results show that chlorisondamine was able to only partially reverse morphine's inhibitory effects. The results clearly show that morphine-induced immunosuppression is mediated by the MOR and that although some functions are amplified in the presence of CORT or sympathetic activation, the inhibition of IFN-gamma synthesis and activation of macrophage-cytokine synthesis is CORT-independent and only partially dependent on sympathetic activation.

Differential effects of the novel non-peptidic opioid 4-tyrosylamido-6-benzyl-1,2,3,4 tetrahydroquinoline (CGPM-9) on in vitro rat t lymphocyte and macrophage functions

Opioid receptors have been reported on immune cells of several species and shown to subserve effector functions of these cell types. Mu-selective opioid agonists such as morphine are immunosuppressive, whereas certain δ-opioid receptor-selective agonists have been associated with immunopotentiation. We have previously shown that intracerebroventricular administration of the non-peptidic δ-opioid receptor agonists did not alter certain parameters of immunocompetence. In this study, we evaluated the in vitro effects of the novel non-peptidic opioid 4-tyrosylamido-6-benzyl-1,2,3,4 tetrahydroquinoline (CGPM-9) on lymphocyte and macrophage functions. We demonstrated that CGPM-9 enhanced rat thymic lymphocyte proliferative response to concanavalin A (2.85- to 5.5-fold increases), and suppressed LPS-induced nitric oxide (67 to 72 percent reduction) and TNF-α production (46 percent reduction) by peritoneal macrophages, compared with untreated control. The μ-opioid receptor selective antagonist CTOP used at equimolar doses, significantly suppressed the effect of CGPM-9 on lymphocyte and macrophage functions (CTOP alone did not show any effect on lymphocyte or macrophage functions). In summary, CGPM-9 activated thymic lymphocyte proliferation and suppressed macrophage functions by acting at μ-opioid receptors. This suggests that opioid receptors on immunocytes may be coupled to different signaling pathways depending on the cell type and effector function being analyzed. The mechanism (s) associated with the differential effect of CGPM-9 on these immune cells remains to be elucidated. The pharmacotherapeutic potential for compounds such as CGPM-9 which potentiate T lymphocyte proliferation and suppress production of macrophage-derived inflammatory cytokines is substantial in research and clinical medicine.

The role of vitamin E in T-cell differentiation and the decrease of cellular immunity with aging.

The purpose of this study is to investigate the effects of vitamin E on both the decrease of cellular immunity with aging (Section 2) and the differentiation of T-cells in thymus (Section 3). In Section 2, spontaneously hypertensive rats (SHR) as a model for aging were used in this experiment and fed regular (50 IU/kg diet) or a high vitamin E (500 IU/kg diet) diet for 6 weeks. At 12 weeks old, they were killed and assayed. Although proliferation of thymic lymphocytes was significantly decreased in SHR fed the regular diet compared to that of Wistar Kyoto rats (WKY) fed the same diet, the high vitamin E diet induced higher proliferation of thymic lymphocytes in SHR, which was almost the same as that of WKY fed the regular diet. In addition, the expressions of both CD4 and CD8 antigens on CD4+ CD8+ T-cells were also decreased in SHR, which was significantly improved by a high vitamin E diet. These results suggest that a high vitamin E diet enhances thymic lymphocyte proliferation through increased T-cell differentiation in the thymus. Then, the effect of vitamin E on T-cell differentiation in the thymus was investigated by using male Fisher rats. Rats were divided into three groups; vitamin E-free, regular and high vitamin E groups and fed a diet containing various levels of vitamin E (0, 50 and 500 IU/kg diet) for 7 weeks. Although the proportions of CD4+ CD8- and CD4- CD8+ T-cells in thymocytes were significantly greater in the high vitamin E group, the proportion of CD4+ CD8- T-cells inversely decreased in the vitamin E-free group compared to that of the regular group. We have tried to investigate the mechanism on the increased T-cell differentiation in the thymus of rats fed the high vitamin E diet through cytokine production, thymic epithelial cell (TEC) and macrophage functions. As their results, we have found that vitamin E enhances T-cell differentiation through the increase of not macrophage but TEC function in the thymus, which is associated with the increased binding capacity of TEC to immature T-cells via increased expression of the adhesion molecule, ICAM-1. These results suggest that vitamin E is a potent nutrient for promoting health in the aged via the improvement of cellular immunity decreased with aging.

Stimulation of fibroblast proliferation and matrix contraction by wound fluid

Fibroblast proliferation and fibroblast-mediated matrix contraction are critical to wound healing. Different cytokines have been shown to modulate fibroblast functions but little is known about the physiological role of these soluble factors during wound repair. In these experiments we characterized a fibroblast stimulating factor in wound fluid. Wound fluid was obtained from subcutaneously implanted polyvinyl alcohol sponges harvested 10 days post-wounding (pool of 100 Lewis rats). Normal dermal fibroblasts were obtained from Lewis rats by an explant technique, while wound fibroblasts were isolated from sponges harvested 10 days post-wounding. Proliferation in response to 0.5% and 10% fetal bovine serum was assessed by [ 3H]-thymidine incorporation. A fibroblast-populated collagen lattice was used for assaying contractile properties. Wound fibroblasts demonstrated markedly diminished proliferative and enhanced contractile properties compared to normal dermal fibroblasts. 10% wound fluid (v/v) stimulated proliferation of normal dermal fibroblasts (119%, p < 0.001) and wound fibroblasts (103%, p < 0.001). Wound fluid also stimulated collagen gel contraction by normal dermal fibroblasts (24% at 24 hr and 16% at 72 hr, p < 0.01), but not by wound fibroblasts. Separation by Sephadex G-100 gel filtration identified the active factor in wound fluid to have a molecular weight of about 100 kDa. Characterization of the soluble factor showed it to be a protein (ammonium sulfate precipitation), sensitive to trypsin digestion, heat resistant (56°C, 30 min), and neuraminidase resistant. The isoelectric point appeared to be 7.0, as determined by ion exchange chromatography. Mitogenic proliferation of thymic lymphocytes was not affected by the active factor, suggesting cell target specificity. These data demonstrate that the wound environment contains high molecular weight protein(s) that promote fibroblast functions, essential for the healing process.

Inhibition of cytokine-stimulated thymic lymphocyte proliferation by fatty acids: The role of eicosanoids

The effect of individual fatty acids on the proliferation of thymic lymphocytes in response to interleukin-1 (IL-1) was investigated. Proliferation was estimated by measuring [ 3H]thymidine incorporation into the acid insoluble fraction of the thymocytes. A concentration-dependent inhibition (in the range 1–100 μM) in the IL-1-stimulated proliferation was observed with the C 20 fatty acids dihomo-γ-linolenic acid (DGLA), arachidonic acid and eicosapentaenoic acid (EPA). A less pronounced concentration-dependent inhibitory response was observed with the C 18 fatty acids linoleic acid, α-linolenic acid and γ-linolenic acid. Palmitic acid and oleic did not have any effect on either basal or IL-1-stimulated proliferation at concentrations up to 100 μM. The potencies of each fatty acid for this effect at a concentration of 100 μM were: arachidonic acid > EPA ≥ DGLA > linoleic acid . DGLA, arachidonic acid and EPA also attenuated IL-2-stimulated proliferation. The inhibitory action of these fatty acids was not mediated by conversion to prostaglandins or other eicosanoids as the cyclooxygenase inhibitor, ketoprofen and NDGA did not alter their action. Incubation of thymocytes with radiolabelled DGLA and EPA followed by reverse-phase HPLC analysis revealed that DGLA is predominantly converted to a more polar metabolite which is not PGE 1 whereas EPA does not appear to be converted to any other detectable metabolite. The data indicate that the inhibitory actions of fatty acids on cell proliferation do not occur as a result of conversion to other metabolites but may be direct effects. The inhibition of cytokine-stimulated lymphocyte proliferation by unsaturated fatty acids would imply that they may attenuate cell-mediated immune reactions.

1α,25-dihydroxyvitamin D 3 a nd 19-nor-1α,25-dihydroxyvitamin 3 2 suppress immunoglobulin production and thymic lymphocyte proliferation in vivo

BALB/CANNHSD female mice were intraperitoneally (i.p.) injected with 1,25-dihydroxyvitamin D-3 (1,25-(OH) 2D 3) (20 ng/day) or 19-nor-1,25-(OH) 2D 2 (100 ng/day) for 7 days and then give the same dose every other day thereafter until day 17 for measuring cell-mediated immunity and on day 33 for observing immunoglobulin production. To observe Ig production, the mice were immunized with an injection of hemocyanin (150 μg/0.1 ml, i.p.) on day 8. On the day 7, 15 and 20 after immunization, the IgG 1, and on day 17 and 20, the IgG 3 levels in 1,25-(OH) 2D 3 and 19-nor-1,25-(OH) 2D 2 groups were significantly lower than in the control group. To measure cell-mediated immunity, mice were sensitized with dinitrofluorobenzene (DNFB) on the shaved abdominal skin. The number of thymic lymphocytes and teir stimulation index were significantly reduced by 1,25-(OH) 2D 3 and 19-nor-1,25-(OH) 2D 2. These results demonstrate that 1,25-(OH) 2D 3 and 19-nor-1,25-(OH) 2D 2 can suppress immunoglobulin production and thymic lymphocyte proliferation in vivo. 19-Nor-1,25-(OH) 2D 2 at doses of 100 ng/day was less effective than 1,25-(OH) 2D 3 at doses of 20 ng/day.

Synthesis and mitogenic activity of new imidazo[2,1- b]thiazoles

Eight new imidazo[2,1- b]thiazoles were synthesized in order to evaluate their ability to stimulate the proliferation of thymic lymphocytes. The 2-chloro ( 5–8) proved more active than the 2,3-dimethyl derivatives ( 1–4): in particular compounds 6 and 7 were more active than levamisole.

Parathyroid hormone stimulation of mitosis in rat thymic lymphocytes is independent of cyclic AMP.

The in vitro mitotic response of rat thymic lymphocytes to hPTH(1-34), hPTH (1-38), and 8,18 Nle hPTH(1-34) exhibits a dependency upon extracellular calcium. Removal of extracellular calcium or the addition of Verapamil (5 micrograms/ml) or trifluoroperazine (10 microM) abrogated the mitotic response. Mitogenic concentrations of 8,18 Nle hPTH(1-34) increased calcium 45 uptake from 4.49 +/- 0.25 to 8.23 +/- 0.75 pMol/10(6) cells/min. The intracellular calcium concentration, measured by Quin 2 fluorescence, also increased after addition of 8,18 Nle hPTH(1-34). Parathyroid hormone-induced activation could not be demonstrated in an otherwise responsive thymocyte membrane adenylate cyclase. In intact cells mitogenic levels of 8,18 Nle hPTH(1-34) decreased intracellular cyclic AMP content. This response was blocked by both 3-isobutyl 1-methyl xanthine and trifluoroperazine, and may indicate activation of calcium-dependent phosphodiesterase. We conclude that PTH stimulates thymic lymphocyte proliferation independently of cyclic AMP, and that changes in cellular calcium homeostasis are intimately involved in the action of PTH. In all of the assays employed, the hitherto antagonistic analogue 8,18 Nle 34 Tyr bPTH(3-34)amide proved to be an agonist. We postulate that the receptor utilized for this PTH action may not exhibit classical PTH structure-activity specificities.

Studies on the thymus from patients with multiple sclerosis and myasthenia gravis

The thymus glands which were excised for therapy (myasthenia gravis; MG) or experimental therapy (multiple sclerosis; MS) were compared to thymic biopsies from patients undergoing cardiac surgery. There was no difference in the weight or total cells of MG and MS thymuses or of the cell density of control, of MG or MS glands. Only 1 of 25 MS thymuses was hyperplastic, as were 2 of 9 of the MG thymuses and none of the controls. Several differences were noted for thymic lymphocyte proliferation to mitogens in MS patients and to antigens in MS and MG patients. MS thymuses had a decreased stimulation index to antithymocyte globulin and to optimal concentrations of pokeweed mitogen. Myasthenia gravis thymuses showed a significantly increased stimulation by myelin basic protein. The %B and %T cell counts were normal for the MS patients. No differences were noted in the incidence of mixed lymphocyte reactions between thymocytes and peripheral lymphocytes in the three groups. Fresh thymic lymphocytes did not suppress concanavalin A stimulated lymphocyte proliferation. It is not known if the differences in lymphocyte proliferation between MS, MG, and control thymuses represent a primary or secondary change.

Requirements for divalent cations by hormonal mitogens and their interactions with sex steroids

Summary Thymic lymphocyte proliferation in vitro may be modulated by a number of hormones. These hormones may be divided into two distinct functional groups based on their requirement for either calcium or magnesium ions in the extracellular milieu. The action of mitogenic hormones which require calcium ions is blocked by oestradiol, whereas the magnesium-dependent hormonal mitogens are ineffectual in the presence of testosterone.

The thymus in relation to problems of cellular growth and ageing.

This review is an attempt to place the thymus in perspective as a special tissue, which by virtue of a high rate of cell division and ease of experimental manipulation, both in vitro and in vivo, offers unique opportunities for answering fundamental questions relating to cellular proliferation. The article begins with an account of the organ’s structure, embryonic origin and evolutionary history. Details of the role of the thymus in immunity have not been included, although current views on this topic have been summarized. Attention is also drawn to old ideas on the role of thymic products in growth and wound healing, which are worthy of further investigation. An argument is presented that the mass of the thymus is maintained as a steady state, regulated mainly by the rate of cellular death, and that organ mass is controlled largely by intrinsic non-humoral mechanisms. An account is given of work on age involution, emphasizing the possible relationship between this phenomenon and deficiencies of the immune system that occur in old age. Particular attention is paid to the role of the steroid endocrine system in age involution. Steroid hormones partly control the balance between cell division and cellular death, but their precise sites and modes of action are far from being established. Sex hormones do not determine the time of onset of age involution, and are not essential for involution to occur. Special reference has been made to the value of the thymus in studies on the ageing of mitotic cells. Recent work has stressed the possibilities of interplay between the various cell types in the tissue which is associated with a shift in the balance between cell populations with age. Morphological changes in both nucleus and cytoplasm of thymic lymphocytes indicate that ageing in these cells proceeds by an epigenetic mechanism. An important new field, with implications for experimental gerontology, is beginning to develop around experiments on thymic transplants. Transplantation work points to the importance of intrinsic processes in the control of cellular proliferation, but shows that systemic factors also play an important part in growth. Both intrinsic and extrinsic influences alter with age. The basic properties of thymic lymphocytes relating to involution change on transplantation, and this finding has important implications for cell biology in general. The final section of the review is devoted to a summary of current views on thymus and cancer. There are several similarities between proliferation of thymic lymphocytes and the growth of certain tumours, suggesting that cellular proliferation in the thymus may be worth studying as a model for work on cancerous growth.

The roles of calcium and cyclic AMP in the stimulatory action of parathyroid hormone on thymic lymphocyte proliferation.

AbstractBoth the parathyroid hormone (PTH) and the calcium ion increase the cellular content of cyclic adenosine 3′,5′‐monophosphate (cyclic AMP), promote the initiation of deoxyribonucleic acid synthesis and stimulate the proliferation of rat thymocytes maintained in vitro. The ability of cyclic AMP to serve as the mediator of the mitogenic actions of both PTH and calcium is established by the fact that cyclic AMP itself stimulates cell proliferation in the absence of PTH and extracellular calcium. Neither PTH nor calcium appear to raise the cellular cyclic AMP level by increasing the nucleotide's synthesis by adenylate cyclase (formerly adenyl cyclase); PTH concentrations as high as 50 μg per ml of medium do not increase the enzyme's activity (in the presence or absence of calcium) and mitogenic calcium concentrations inhibit it. PTH also does not directly affect isolated thymocyte phosphodiesterase, but mitogenic calcium levels inhibit the enzyme's activity. Additional experiments show that it is calcium which raises the cyclic AMP level in cells treated with PTH, and some possible calcium‐mediated mechanisms by which the hormone could elevate the cellular cyclic AMP levels are discussed. Thus, the mitogenic action of PTH is primarily mediated by calcium while cyclic AMP is the ultimate implementor of the hormonal action. However, calcium has a dual role and evidence is presented which indicates that besides raising the cellular cyclic AMP level, it also controls the operation of cyclic AMP's mitogenic end‐reaction.