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S Arkins

Publications and source records attributed to S Arkins.

At least 37 records · Page 2Linked to original sources
PubMed1993

Macrophages suppress lectin-induced proliferation of lymphocytes from aged rats.

Splenocytes from old rats exhibit a significant reduction in proliferative responses to Con A. This defect can be overcome by passing the cells over nylon wool, which suggests that nylon wool adherent cells contribute to the reduction in proliferation of mixed cell populations from aged rats. To examine the potential role of macrophages in this process, thioglycollate-elicited peritoneal macrophages were added to Con A-activated spleen cells from young and old rats. Addition of as few as 3% macrophages suppressed proliferation of Con-A-activated splenocytes and this inhibition was significantly greater if either the macrophages or spleen cells were derived from aged rats. Although prostaglandin E2 (PG-E2) inhibited the proliferation of splenocytes and nylon-wool enriched splenocytes from 3-month-old animals, its suppressive effects were much greater on Con A-activated lymphocytes derived from 24-month-old rats. Addition of catalase to deplete macrophage-derived H2O2 resulted in greater augmentation of Con-A-induced proliferative responses of splenocytes from old rats than those from young rats. TGF-beta 2, but not TNF-alpha, also significantly suppressed the proliferation of Con A-activated splenocytes to a greater degree in aged than in young rats. Since macrophages are known to release PG-E2, H2O2 and TGF-beta 2 after stimulation with Con A, these data support the idea that T cells within the splenocyte population become increasingly susceptible during aging to inhibitory products released by macrophages.

Aging↗
PubMed1993

Molecular identification of two types of interleukin-1 receptors in the murine pituitary gland.

The present study was carried out to characterize interleukin-1 (IL-1) receptors on murine pituitary cells. Receptor autoradiography confirmed the existence of binding sites for IL-1 alpha in the murine adenohypophysis, but not in the neural or intermediate lobes. Specific binding of IL-1 to isolated pituitary membranes revealed a Kd of 0.9 nM with a Bmax of 37 fmol/mg protein. To examine the possibility that the adenohypophysis synthesizes a receptor for IL-1, immunocytochemistry experiments with a specific monoclonal antibody against the type I receptor revealed the existence of this protein in only the adenohypophysis. Identity of the type I IL-1 receptor was similar to that found on T cells as determined by: 1) amplification of the predicted 619 bp fragment spanning the cytoplasmic, transmembrane and extracellular domains from RNA of pituitary and T cell origin, as well as clonal AtT-20 pituitary cells, and 2) restriction fragment analysis and sequencing of the amplified cDNAs. The pituitary gland and AtT-20 cells also expressed transcripts for the newly identified type II receptor for IL-1 as assessed by amplification of a specific 325 bp fragment, restriction fragment analysis and nucleotide sequencing, and these transcripts were similar to those found on B lymphocytes. These data identify two different forms of the IL-1 receptor in both normal and transformed pituitary cells and establish that these receptors are similar at the molecular level to those first identified on T and B lymphocytes.

Animals↗
PubMed1993

Murine macrophages express abundant insulin-like growth factor-I class I Ea and Eb transcripts.

Hemopoietic cells have been reported to synthesize insulin-like growth factor-I (IGF-I) messenger RNA (mRNA), but the relative contribution of specific cell lineages that express these transcripts remains unknown. Reverse transcription and amplification of complementary DNA (cDNA) by the polymerase chain reaction were used to characterize full-length IGF-I mRNA transcripts in murine hemopoietic cells. The identity of transcripts encoding the entire prepropeptide was confirmed by restriction endonuclease digestion, Southern blotting, cloning, and Sanger sequencing. Abundance of IGF-I mRNA transcripts was assessed both by Northern blotting and sensitive ribonuclease protection assays followed by quantification with Phosphor-Imager analysis. Whereas IGF-I cDNA transcripts could be detected in a variety of leukocytes after polymerase chain reaction amplification, IGF-I mRNA was negligible or nondetectable in T and B cell lines and in those tissues containing a predominance of these cell types (e.g. spleen and thymus) by Northern blotting and ribonuclease protection assays. In contrast, elicited peritoneal macrophages, a macrophage cell line, microglia, and bone marrow macrophages differentiated in vitro expressed abundant IGF-I mRNA transcripts, whereas neither a premyeloid cell line nor freshly isolated bone marrow cells expressed significant transcripts. The 5'-identity of macrophage IGF-I transcripts was established using an exon 2-derived IGF-I cDNA probe. All protected transcripts were foreshortened, indicating transcript initiation exclusively within exon 1, characteristic of extra-hepatic IGF-I mRNA. However, at the 3'-end, both IGF-I Ea (lacking exon 5) and IGF-I Eb (containing exon 5) mRNA transcripts were evident, with the Eb product being detected at levels similar to those present in hepatic cellular RNA. A large molecular size (26 kilodaltons) prepro-IGF-I peptide was also detected in macrophage cell lysates by Western blotting. Collectively, our observations show that: 1) among hemopoietic cells, myeloid rather than lymphoid cells are the major source of IGF-I; 2) macrophage IGF-I mRNA consists of class I Ea and Eb transcripts; 3) these transcripts are translated into protein; and 4) expression of IGF-I is directly associated with differentiation of bone marrow macrophages.

Animals↗
PubMed1993

Somatolactogens, somatomedins, and immunity.

The neuroendocrine and immune systems participate as active partners in host homeostatic and defense mechanisms. This partnership involves a complex intercommunication system employing an array of shared ligands and receptors. Hormones of the somatolactogen family have marked influences on immune events in vivo, including the maintenance of lymphoid tissue cellularity, the promotion of DNA synthesis in these tissues, and the stimulation of a number of immune effector mechanisms. Both growth hormone and prolactin function to promote erythropoiesis and DNA synthesis in bone marrow precursors. Our results have shown that the somatolactogens and a member of the somatomedin family, IGF-I, are particularly effective in modulating the effector functions in phagocytic cells, including the production of reactive oxygen intermediates and tumor necrosis factor-alpha and the oxygen-dependent killing of bacteria. Evidence indicating a role of IGF-I in modulating immune functions is more recent but nonetheless compelling. Accumulated data suggest that somatolactogenic hormones, as well as one member of the somatomedins, are produced by cells of the immune system and can regulate local immune events. Although the molecular mechanisms by which the somatolactogens and somatomedins exert their effects on immune tissues are only now being explored, the pleiotropic nature of these effects suggests that these hormones participate at endocrine, paracrine, and perhaps autocrine sites of action.

Animals↗
PubMed1992

Prolactin synthesized and secreted by human peripheral blood mononuclear cells: an autocrine growth factor for lymphoproliferation.

Prolactin has been shown to have an immunoregulatory role in the rodent immune response. A prolactin-like molecule has also been found in mouse splenocytes and a human B-lymphoblastoid cell line. We have evaluated whether human peripheral blood mononuclear cells (PBMCs) synthesize and/or secrete prolactin. We used the polymerase chain reaction (PCR) to generate a 276-base-pair prolactin product from human PBMCs, and Southern blot analysis confirmed that it was related to prolactin. Western blotting using a polyclonal antibody to prolactin indicated that cell extracts prepared from human PBMCs contained a high molecular mass (60-kDa) immunoreactive prolactin. To determine whether this PBMC prolactin was being secreted, we developed a highly sensitive and specific hormonal enzyme-linked immunoplaque assay. With this assay, we were able to detect human prolactin secretion from concanavalin A (Con A)- or phytohemagglutinin-stimulated PBMCs but not from unstimulated PBMCs. We next sought to determine whether this secreted prolactin could function as an autocrine growth factor in lymphoproliferation. We observed that anti-human prolactin antiserum significantly inhibited human PBMC proliferation in response to Con A or phytohemagglutinin. We conclude that a prolactin-like molecule is synthesized and secreted by human PBMCs and that it functions in an autocrine manner as a growth factor for lymphoproliferation.

Base Sequence↗
PubMed1992

The macrophage-activating properties of growth hormone.

1. We compared the ability of growth hormone (GH) and a well-characterized macrophage-activating factor, interferon-gamma (IFN-gamma) to activate highly purified populations of alveolar macrophages. Both GH and IFN-gamma primed macrophages triggered with opsonized zymosan to secrete superoxide anion (O2-) in vitro, but IFN-gamma was effective at a 40-fold lower concentration. Antibody blocking studies demonstrated that the priming activity of GH was independent of IFN-gamma, and the activity of IFN-gamma was distinct from that of GH. 2. Both IFN-gamma and GH increased the capability of macrophages to kill Pasteurella multocida in vitro. 3. Hypophysectomized rats challenged with Salmonella typhimurium were significantly protected by injections of either GH or recombinant rat IFN-gamma in vivo compared to vehicle-treated controls, and the protective effect of GH was increased by incorporation into liposomes. 4. Insulin-like growth factor-I (IGF-I) also primed alveolar macrophages in vitro, which is consistent with the idea that the protective effects of GH in vivo might be mediated by augmenting the synthesis of IGF-I. These data support the concept of reciprocal systems of communication between the neuroendocrine and immune systems.

Animals↗
PubMed1992

Photodestruction of tumor cells by induction of endogenous accumulation of protoporphyrin IX: enhancement by 1,10-phenanthroline.

Rapidly proliferating transformed mammalian cells can be photodestroyed in vitro upon inducing the accumulation of endogenous protoporphyrin IX (Proto). Proto biosynthesis and accumulation were triggered by manipulation of the porphyrin-heme biosynthetic pathway. Proto accumulation in cultured cells was induced by treatment with 1.0 mM delta-aminolevulinic acid (ALA), a naturally occurring 5-carbon amino acid, for 3.5 h. In darkness, significant Proto accumulation became evident within 3.5 h of incubation. In the light, the accumulated tetrapyrroles triggered destruction of treated cells within the first 30 min of illumination, probably via the rapid oxidation of cellular constituents by singlet oxygen. Protoporphyrin IX accumulation and specific cell lysis increased significantly by inclusion of 0.75 mM 1,10-phenanthroline (Oph), a tetrapyrrole biosynthesis modulator. Slower growing untransformed cells did not accumulate significant amounts of Proto following ALA and Oph treatment unless stimulated to proliferate with the mitogenic lectin Concanavalin A.

Aminolevulinic Acid↗
PubMed1992

In vivo administration of recombinant growth hormone or gamma interferon activities macrophages: enhanced resistance to experimental Salmonella typhimurium infection is correlated with generation of reactive oxygen intermediates.

Purified and recombinant forms of growth hormone (GH) as well as of recombinant rat gamma interferon (IFN-gamma) enhance the survival of rats deprived of endogenous pituitary GH secretion by hypophysectomy (HX rats) and infected with virulent Salmonella typhimurium. Macrophages obtained from rats with intact pituitaries (pituitary-intact rats) or HX rats that were treated in vivo with either GH or the closely related hormone prolactin released elevated (P less than 0.05) levels of superoxide anion (O2-) after in vitro opsonized-zymosan stimulation compared with those from placebo-treated animals. These levels of O2- release were similar in magnitude to those of macrophages from rats treated in vivo with IFN-gamma. In time course in vivo macrophage activation studies, both IFN-gamma and GH significantly increased O2- secretion within 24 h, with maximal secretion occurring at day 3. Macrophages obtained from pituitary-intact and HX rats injected in vivo with GH also released elevated (P less than 0.05) levels of hydrogen peroxide (H2O2) and displayed enhanced (P less than 0.01) phagocytic activity toward opsonized Listeria monocytogenes in vitro. The mechanism of action of GH in vivo is likely to be a direct one because resident peritoneal macrophages from rats could be primed in vitro for enhanced secretion of O2- following triggering of these cells with opsonized zymosan. These data show that in vivo administration of two closely related pituitary hormones, GH and prolactin, can effectively prime macrophages, which is consistent with the hypothesis that GH mediates resistance to S. typhimurium by a direct stimulatory action on macrophages.

Animals↗
PubMed1992

Growth hormone augments superoxide anion secretion of human neutrophils by binding to the prolactin receptor.

Recombinant human growth hormone (HuGH) and human prolactin (HuPRL), but not GH of bovine or porcine origin, prime human neutrophils for enhanced superoxide anion (O2-) secretion. Since HuGH, but not GH of other species, effectively binds to the HuPRL receptor (HuPRL-R), we used a group of HuGH variants created by site-directed mutagenesis to identify the receptor on human neutrophils responsible for HuGH priming. A monoclonal antibody (MAb) directed against the HuPRL-R completely abrogated O2- secretion by neutrophils incubated with either HuGH or HuPRL, whereas a MAb to the HuGH-R had no effect. The HuGH variant K172A/F176A, which has reduced affinity for both the HuGH-binding protein (BP) and the HuPRL-BP, was unable to prime human neutrophils. This indicates that priming is initiated by a ligand-receptor interaction, the affinity of which is near that defined for receptors for PRL and GH. Another HuGH variant, K168A/E174A, which has relatively low affinity for the HuPRL-BP but slightly increased affinity for the HuGH-BP, had much reduced ability to prime neutrophils. In contrast, HuGH variant E56D/R64M, which has a similar affinity as wild-type HuGH for the HuPRL-BP but a lower affinity for the HuGH-BP, primed neutrophils as effectively as the wild-type HuGH. Finally, binding of HuGH to the HuPRL-BP but not to the HuGH-BP has been shown to be zinc dependent, and priming of neutrophils by HuGH was also responsive to zinc. Collectively, these data directly couple the binding of HuGH to the HuPRL-R with one aspect of functional activation of human target cells.

Adult↗
PubMed1991

A novel role of growth hormone and insulin-like growth factor-I. Priming neutrophils for superoxide anion secretion.

Growth hormone (GH) and the GH-dependent growth promoting peptide, insulin-like growth factor-I (IGF-I), are both potent signals for priming human and porcine polymorphonuclear neutrophils (PMN) to secrete superoxide anion (O2-). PMA, opsonized-zymosan, or FMLP could all be used as triggering stimuli to demonstrate priming by GH or IGF-I. As positive controls, IFN-gamma and LPS also primed both human and porcine PMN for enhanced O2- release. However, only the LPS-mediated enhancement was inhibited by polymyxin B, which demonstrates that the priming induced by GH, IGF-I, or IFN-gamma was not caused by LPS contamination. Furthermore, a specific antibody to GH abrogated priming induced by this molecule. In contrast to IGF-I, the closely related molecule insulin was unable to prime PMN even at pharmacologic levels. Insulin, at pharmacologic levels, antagonized the priming mediated by IGF-I but had no effect on GH priming. A mAb directed against the human IGF-I receptor blocked the enhanced secretion of O2- by human PMN that was caused by IGF-I, but not GH, indicating that neutrophil priming induced by GH was not mediated by inducing extracellular release of IGF-I. However, priming PMN by both GH and IGF-I required de novo protein synthesis, because cycloheximide completely abrogated enhanced O2- secretion that was caused by these growth factors. These data show that a classic pituitary hormone (GH), as well as its widely recognized growth promoting peptide (IGF-I), are involved in regulating an important functional activity of both porcine and human PMN. Inasmuch as GH and IGF-I have recently been demonstrated to be synthesized by leukocytes, these data support the possibility that both of these proteins could act in a paracrine fashion as cytokines to prime PMN for an enhanced respiratory burst.

Adult↗
PubMed1991

Hypophysectomy inhibits the synthesis of tumor necrosis factor alpha by rat macrophages: partial restoration by exogenous growth hormone or interferon gamma.

We recently demonstrated that GH and interferon-gamma (IFN gamma) act in a similar manner to prime macrophages in vitro and in vivo for enhanced superoxide anion release. In this report we investigated the physiological role of the pituitary gland and GH in in vivo priming of resident peritoneal macrophages for the synthesis of tumor necrosis factor-alpha (TNF alpha) in vitro. Compared to normal rats, hypophysectomized animals had an 83% reduction in macrophage production of TNF alpha after in vitro stimulation with lipopolysaccharide. Sham operation had no significant effect on the ability of macrophages to secrete TNF alpha in response to lipopolysaccharide. Both native pituitary-derived porcine GH (48 micrograms/rat.9 days) and native pituitary-derived rat GH (96 micrograms/rat.9 days) more than tripled the in vitro production of TNF alpha by macrophages from hypophysectomized rats (342 and 358 vs. 112 U/mg protein for placebo-treated rats, respectively). Each of these preparations of GH also increased growth more than 6-fold in hypophysectomized rats (32 and 30 g vs. 5 g in placebo controls). Heat inactivation of native pituitary-derived porcine GH significantly reduced its in vivo ability to augment both TNF alpha synthesis by macrophages and body growth. Recombinant rat IFN gamma (2000 U/rat.9 days) more than tripled the production of TNF alpha by macrophages from hypophysectomized rats (343 vs. 112 U/mg protein). In contrast to its in vivo effects, addition of GH in vitro to macrophages from hypophysectomized rats did not prime these cells for the synthesis of TNF alpha, indicating an indirect mechanism of action for GH. To further test the biological relevancy of GH with respect to synthesis of TNF alpha, hemorrhagic necrosis of TNF alpha-sensitive murine methyl-cholanthrene-induced tumors was assessed in pituitary-intact mice. Native porcine GH (133 micrograms/mouse.7 days) significantly augmented both the necrosis to tumor ratio and the hemorrhage to tumor ratio. These findings establish the physiological relevance of the pituitary gland and GH in the priming of macrophages for TNF alpha synthesis.

Animals↗
PubMed1990

The proliferative response of rat T cells to calcium ionophores increases with age.

Splenocytes and T cells from both old and young rats proliferate to A23187 and ionomycin, and this response increases 3- to 10-fold in aged animals. Augmented responsiveness to ionomycin occurs in the absence of any defect in Con A-induced proliferation of T lymphocytes of aged rats and is dependent upon the addition of thiol compounds to the tissue culture medium. Augmented proliferative responses to ionomycin precede the significant but much smaller decline (30 to 40%) in Con A-induced proliferative responsiveness of splenocytes, which is evident only when rats reach 24 months of age. Heightened proliferation to calcium ionophores is not caused by a greater ability of T lymphocytes from aged rats to increase [Ca2+]i in response to ionomycin. The increased proliferative response of lymphocytes from aged rats to ionomycin occurs in the absence of detectable amounts of secreted IL 2 or IL 4. The ionophore response is a much more sensitive biomarker of age than the decline in Con A-induced proliferative responses of lymphocytes and identifies an activity of T lymphocytes that increases rather than decreases during the aging process.

Aging↗
PubMed1990

Role of interferon-gamma in counteracting the suppressive effects of transforming growth factor-beta 2 and glucocorticoids on the production of tumor necrosis factor-alpha.

The multipotential cytokine, transforming growth factor-beta 2 (TGF-beta 2), is as effective as glucocorticoids in suppressing the production of tumor necrosis factor-alpha (TNF-alpha) by lipopolysaccharide (LPS)-stimulated macrophages, and this inhibition can be abrogated by exogenous interferon-gamma (IFN-gamma). Porcine alveolar macrophages triggered with LPS produce TNF-alpha as identified by complete blocking of cytotoxicity on WEHI 164 clone 13 cells in macrophage supernatants by a monoclonal antibody to human TNF-alpha. Platelet-derived porcine TGF-beta 2, at a concentration of 4 nM, inhibited LPS-induced production of TNF-alpha by 93%. Dexamethasone was as effective as TGF-beta 2, suppressing TNF-alpha production by 86% at a concentration of 4 nM. The natural but less potent glucocorticoid cortisol inhibited TNF-alpha production by 100% at a 100-fold higher concentration (400 nM). Recombinant PoIFN-gamma consistently primed LPS-triggered macrophages for increased production of TNF-alpha by 50-100%, and this priming was totally blocked by a polyclonal antibody to rPoIFN-gamma. Furthermore, the suppression in LPS-induced production of TNF-alpha caused by TGF-beta 2, dexamethasone, and cortisol could be reversed by addition of rPoIFN-gamma. These data show that alveolar macrophages can be effectively primed by rPoIFN-gamma even in the presence of moderately suppressive doses of TGF-beta 2 and antiinflammatory steroids.

Animals↗
PubMed1990

Glutathione augments in vitro proliferative responses of lymphocytes to concanavalin A to a greater degree in old than in young rats.

The proliferative response of splenocytes to concanavalin A (Con A) is significantly lower in aged than in young rats. The addition of reduced (GSH) but not oxidized (GSSG) gamma-glutamylcysteinyl-glycine (glutathione) in vitro totally reverses the defective proliferative response of splenocytes from aged rats. The inhibitor of gamma-glutamylcysteine synthetase, buthionine sulfoximine, abrogates the in vitro proliferation of splenocytes from young rats activated with Con A, and this effect is significantly reversed by addition of GSH. The enhancing effects of GSH on proliferation of Con A-activated splenocytes of both young and old rats are apparent as early as 24 h and are still evident as late as 72 h in culture. Both cysteine and 2-mercaptoethanol are able to mimic the effect of GSH in causing a greater increase in Con A-induced proliferative responses of splenocytes from old rats (eightfold) as compared to young animals (threefold). Although 2-mercaptoethanol increases expression of membrane-bound transferrin receptors on both Con A-activated splenocytes and T lymphocytes, this alone does not account for the greater enhancement of Con A-induced proliferation of splenocytes from old as compared to young rats. These data are consistent with the hypothesis that the glutathione peroxidase-dependent detoxification system is defective in T lymphocytes of aged rats.

Aging↗
PubMed1990

Interferon-gamma-induced priming for secretion of superoxide anion and tumor necrosis factor-alpha declines in macrophages from aged rats.

Macrophage responses to recombinant IFN-gamma decline during aging, as measured by two criteria of macrophage activation, O2- and TNF-alpha secretion. The production of O2- by macrophages in response to opsonized-zymosan and recombinant rat IFN-gamma is 75% lower in 23-month-old rats than in 3-month-old rats. Furthermore, the secretion of TNF-alpha in response to IFN-gamma and LPS is almost absent in macrophages from aged rats. Production of both O2- and TNF-alpha by resident peritoneal macrophages from specific pathogen-free aged rats in response to priming and triggering stimuli was partially or fully restored by implantation of syngeneic pituitary grafts from young rats. These data demonstrate that macrophages from aged rats are defective in their response to a priming signal induced by IFN-gamma, and they suggest that impaired macrophage responses during aging may be reversible.

Aging↗
PubMed1989

Bilateral removal of the cauda epididymides in the neonatal pig as a technique for creating teaser boars.

Five pairs of crossbred littermate boars were used to assess the efficacy of bilateral removal of the cauda epididymides at an early age as a technique for creating teaser boars. The cauda epididymides were surgically removed in one of each litter pair; the other of the pair served as an intact control. Boars subjected to removal of the epididymides (Epid) were rendered sterile by the technique. The Epid-treated and control untreated littermate boars had similar levels of sexual aggression and libido, as measured by behavioral characteristics at semen collection. The Epid-treated boars showed a slight, but not significant, reduction in ejaculate volume. Upon slaughter at 273 d of age, Epid and control boars had similar weights for the accessory sexual organs and penis and similar penile lengths. The Epid-treated boars displayed enlarged caput epididymides and granulomata. It is suggested that bilateral removal of the cauda epididymides in the neonatal pig may prove a worthwhile alternative to the traditional vasectomy procedure to create teaser boars.

Animals↗
PubMed1988

A pituitary-thymus connection during aging.

Thymic involution is a normal consequence of aging. It has often been speculated that if this age-associated atrophy of the thymus gland could be prevented, the natural decline that occurs in a number of T-cell-mediated immune responses could be reversed. It has recently become clear that thymic involution can indeed be reversed by altering the hormonal environment of aged animals. These data support the concept of an active and functional pituitary-thymus axis. Since thymic reconstitution can result in restoration of some T-cell responses, it would appear that intrinsic defects which exist in T cells of aged animals can be at least partially reversed. This suggests that the aged environment plays a greater role in the decline of T-cell functions than has been previously recognized. Furthermore, phorbol esters and calcium ionophores can restore suppressed proliferative responses of T cells from aged rodents, so we speculate that intrinsic defects in T cells of aged subjects lie between the recognition system for antigen/lectin and intracellular transmission of this signal.

Aging↗