The living record of
peptide science.

Zinc and immune function: the biological basis of altered resistance to infection.

Am J Clin Nutr

A H Shankar, A S Prasad

Zinc is known to play a central role in the immune system, and zinc-deficient persons experience increased susceptibility to a variety of pathogens. The immunologic mechanisms whereby zinc modulates increased susceptibility to infection have been studied for several decades. It is clear that zinc affects multiple aspects of the immune system, from the barrier of the skin to gene regulation within lymphocytes. Zinc is crucial for normal development and function of cells mediating nonspecific immunity such as neutrophils and natural killer cells. Zinc deficiency also affects development of acquired immunity by preventing both the outgrowth and certain functions of T lymphocytes such as activation, Th1 cytokine production, and B lymphocyte help. Likewise, B lymphocyte development and antibody production, particularly immunoglobulin G, is compromised. The macrophage, a pivotal cell in many immunologic functions, is adversely affected by zinc deficiency, which can dysregulate intracellular killing, cytokine production, and phagocytosis. The effects of zinc on these key immunologic mediators is rooted in the myriad roles for zinc in basic cellular functions such as DNA replication, RNA transcription, cell division, and cell activation. Apoptosis is potentiated by zinc deficiency. Zinc also functions as an antioxidant and can stabilize membranes. This review explores these aspects of zinc biology of the immune system and attempts to provide a biological basis for the altered host resistance to infections observed during zinc deficiency and supplementation.

Zinc, thymic endocrine activity and mitogen responsiveness (PHA) in piglets exposed to maternal aflatoxicosis B1 and G1.

Vet Immunol Immunopathol

E Mocchegiani, A Corradi, L Santarelli +6 more

Growth retardation, thymic involution and impaired peripheral immune efficiency are constant events in piglets exposed to maternal aflatoxicosis. Zinc may play a key role because of its requirement for good immune responses, including thymic endocrine activity. Zinc is required to activate a thymic hormone, i.e. thymulin (ZnFTS), which is responsible for cell-mediated immunity. Zinc deficiency and decreased thymic endocrine activity are present in piglets fed from sows exposed to aflatoxins (AF) B1 and G1 as compared with healthy control piglets. In particular, active ZnFTS is decreased while concentrations of inactive thymulin (FTS) are high. The in vitro addition of zinc up to the plasma samples induces a reduction of inactive thymulin. The lymphocytes mitogen responsiveness (PHA) is decreased and a thymic cortical lymphocyte depletion is also present. These data suggest that the thymic defect, followed by impaired peripheral immune efficiency, may largely depend by the low peripheral zinc bioavailability to saturate all thymulin molecules produced.

Thymic endocrinology.

Ann N Y Acad Sci

J W Hadden

The thymus involutes relatively early in life; cellular immune deficiencies of aging correspond to decline in function of the hypothalamic-pituitary-endocrine axis. Recent studies point to important roles for the pituitary, the pineal, and the autonomic nervous system as well as the thyroid, gonads and adrenals in the thymus integrity and function. Thymic function at the local level requires complex cellular interactions among thymic stromal cells and developing thymocytes involving paracrine and autocrine mediators including interleukins (ILs) 1, 2, 6, 7, 8, colony-stimulating factors (CSFs), interferon-gamma, thymosin alpha 1, and zinc-thymulin. An important endocrine function of the thymus is to package zinc in zinc-thymulin for delivery to the periphery. Thymic involution has been treated with interleukins, thymic hormones, growth hormone, prolactin, melatonin, zinc, and others. Our work to reverse thymic involution in hydrocortisone-treated, aged mice with interleukins, thymosin alpha 1, and zinc will be reviewed. Recent efforts to treat successfully immune deficiency in aged and cancer-bearing humans will be presented.

Coadministration of galanin antagonist M40 with a muscarinic M1 agonist improves delayed nonmatching to position choice accuracy in rats with cholinergic lesions.

J Neurosci

M P McDonald, L B Willard, G L Wenk +1 more

The neuropeptide galanin is overexpressed in the basal forebrain in Alzheimer's disease (AD). In rats, galanin inhibits evoked hippocampal acetylcholine release and impairs performance on several memory tasks, including delayed nonmatching to position (DNMTP). Galanin(1-13)-Pro2-(Ala-Leu)2-Ala-NH2 (M40), a peptidergic galanin receptor ligand, has been shown to block galanin-induced impairment on DNMTP in rats. M40 injected alone, however, does not improve DNMTP choice accuracy deficits in rats with selective cholinergic immunotoxic lesions of the basal forebrain. The present experiments used a strategy of combining M40 with an M1 cholinergic agonist in rats lesioned with the cholinergic immunotoxin 192IgG-saporin. Coadministration of intraventricular M40 with intraperitoneal 3-(3-S-n-pentyl-1,2,5-thiadiazol-4-yl)-1,2,5, 6-tetrahydro-1-methylpyridine (TZTP), an M1 agonist, improved choice accuracy significantly more than a threshold dose of TZTP alone. These results suggest that a galanin antagonist may enhance the efficacy of cholinergic treatments for the cognitive deficits of AD.

New analogs of human growth hormone-releasing hormone (1-29) with high and prolonged antagonistic activity.

J Pept Res

K Toth, M Kovacs, M Zarandi +5 more

Based on our previous results, in conjunction with various structural considerations, 19 new analogs of the GHRH antagonist [PhAc-Tyr1,D-Arg2,Phe(pCl)6,Abu15,Nle27,Agm29]++ +hGHRH(1-29) (MZ-5-156) were synthesized by the solid-phase method. These compounds were designed to develop further analogs of this class with increased receptor-binding affinity. All analogs had Abu15 and Nle27 modifications and were acylated with phenylacetic acid at the N-terminus. Most of the analogs had D-Arg2 and Phe(pCl)6 substituents and Agm29 or Arg29-NH2 at the C-terminus. Additional single substitutions consisted of the incorporation of D- or L-Tic1, D-Tic2, Tic6 or Phe(pNO2)6 and Arg29-NH2. The Arg29-NH2 analog of MZ-5-156 (KT-48) was further modified by single substitutions using Pal1; D-Tpi2; D- or L-Phe4; Phe(pX)6 X = F, Cl, I; Tyr7; Aib8; Tyr(Me)10 or Phe(pCl)10. Four peptides had multiple substitutions. All the analogs were evaluated for their ability to inhibit GH release induced by hGHRH(1-29)NH2 in vitro and some were also tested in vivo. Peptides [PhAc-Tyr1,D-Arg2,Phe(pI)6,Abu15,Nle27]hGHRH(1-2 9)NH2 (KT-30), [PhAc-Tyr1,D-Arg2,Phe(pCl)6,Aib8,Abu15,Nle27] hGHRH(1-29)NH2 (KT-50) and [PhAc-Tyr1,D-Arg2,Phe(pCl)6,Tyr(Me)10,Abu15,Nle27]h GHRH(1-29)NH2 (KT-40) with Phe(pI)6, Aib8 or Tyr(Me)10 modifications, respectively, showed high and prolonged inhibitory effect in superfused rat pituitary system. Analog KT-50 also exhibited a strong and long-term inhibitory activity in vivo in rats. Most of the new analogs showed high binding affinities to rat pituitary GHRH receptors.

Galanin-acetylcholine interactions in rodent memory tasks and Alzheimer's disease.

J Psychiatry Neurosci

M P McDonald, J N Crawley

Galanin is a 29-amino-acid neuropeptide that is widely distributed in the mammalian central nervous system. Galanin-immunoreactive cell bodies, fibres and terminals, and galanin binding sites, are located in the basal forebrain of rats, monkeys and humans. Galanin fibres hyperinnervate the surviving cholinergic cell bodies in patients with Alzheimer's disease (AD). In rats, galanin inhibits acetylcholine release and produces deficits in learning and memory. These findings suggest that overexpressed galanin may contribute to the cognitive impairments exhibited by patients with AD. This paper reviews the literature on galanin distribution and function in light of its putative role in the mnemonic deficits in patients with AD, the effects of galanin on tests of learning and memory, and preliminary experiments with galanin antagonists in animal models of AD.

The major metabolite of dipeptide piracetam analogue GVS-111 in rat brain and its similarity to endogenous neuropeptide cyclo-L-prolylglycine.

Eur J Drug Metab Pharmacokinet

T A Gudasheva, S S Boyko, R U Ostrovskaya +7 more

The metabolism of a new piracetam analogue, the dipeptide cognitive enhancer N-phenylacetyl-L-prolylglycine ethyl ester (GVS-111) was studied in vivo. GVS-111 itself was not found in rat brain 1 h after 5 mg/kg i.p. administration up to limit of detection (LOD) under high performance liquid chromatography (HPLC) conditions. Three substances corresponding to the three possible GVS-111 metabolites, namely phenylacetic acid, prolylglycine and cyclo-prolylglycine, were found in experimental rat brain samples as well as in controls using HPLC, gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) methods. Only cyclo-prolylglycine concentration increased (2.5-fold) 1 h after GVS-111 administration. Cyclo-prolylglycine formation from GVS-111 in the presence of plasma and brain enzymes was shown in vitro. These data could be considered as evidence that GVS-111 is prodrug which converts in the body to cyclo-prolylglycine, and which is identical to the endogenous cyclopeptide that produces the nootropic activity.

Effect of neuropeptides on cognitive function.

Exp Gerontol

G W Bennett, T M Ballard, C D Watson +1 more

Recent evidence indicates that, in addition to the involvement of cholinergic and other neurotransmitter systems, various neuropeptides that occur in cortical and subcortical brain regions have a role in cognitive behavior. This evidence results largely from behavioral studies in rodents and other animals, following peptide administration and only in a very few cases from similar studies in human subjects. Several neuropeptides studied appear to enhance or produce changes conducive to improvement in cognitive performance and these include vasopressin, corticotrophin-releasing hormone (CRH), somatostatin, substance P, neuropeptide Y, and thyrotrophin-releasing hormone (TRH), while one peptide, galanin, has been reported to inhibit cognitive processes. Of those neuropeptides that improve performance, only TRH has been shown recently to attenuate the memory impairment of human subjects and Alzheimer patients treated with an anticholinergic drug, and this review describes a series of complimentary studies in adult and aged rodents that contribute to our understanding of the possible mechanisms involved in the role of TRH in cognition.

Zinc and metallothioneins on cellular immune effectiveness during liver regeneration in young and old mice.

Life Sci

E Mocchegiani, D Verbanac, L Santarelli +4 more

Partial hepatectomy in young mice (pHx) induces thymic atrophy, disregulation of thymocytes subsets and a strong accumulation of zinc in thymic tissue after 1-2 days of liver regeneration. Zinc is relevant for good immune functioning. Restoration of zinc into both the thymus and thymocytes subsets in the late period of liver regeneration is observed in young pHx mice. These findings have suggested a link between the thymus and the liver influencing T-cell functions and involving zinc. This kind of link could be relevant in aging because thymic involution, negative crude zinc balance and crippled immune functions are constant events. The preminence of a liver extrathymic T-cell pathway after pHx or during aging has been suggested. Thus the study of pHx in young and old mice may offer a good model to better understand the role played both by thymic involution and by liver extrathymic T-cell pathway and the role of zinc in these physiological processes during aging. Young pHx mice after 1-2 days of liver regeneration show: reduced thymic endocrine activity, increment of double negative (DN) thymocytes subsets, impairment of peripheral immune efficiency (PHA, NK activity and IL-2) and negative crude zinc balance, which are all restored in the late period of liver regeneration. By contrast the thymic and peripheral immune defects and the negative crude zinc balance, already present in old sham mice, are not modified during liver regeneration in old pHx mice. Circulating leukocytes and lymphocytes are not significantly modified both in young and old pHx mice as compared to respective sham controls. Zinc may also be crucial for extrathymic T-cells pathway, being preminent in aging, rather than in young age, due to its metallothioneins (MT) binding capacity. MT are significantly increased in young pHx and in aging inducing a low zinc-free quota for thymic and peripheral immune efficiency in young pHx mice, and for extrathymic T-cell pathway, in old age. Thus low zinc bioavailability, due to MT, may play a pivotal role, not only for thymocytes but also for liver extrathymic T-cell pathway.

Zinc-controlled Th1/Th2 switch significantly determines development of diseases.

Med Hypotheses

J E Sprietsma

Functional, excessive-possibly temporary-deficiencies of the trace element zinc can change immune functions prematurely from predominantly cellular Th1 responses to humoral Th2 responses. T helper (Th1) cells produce cytokines such as interleukin-2 (IL-2) and interferon gamma, thereby controlling viral infections and other intracellular pathogens more effectively than Th2 responses through cytokines such as IL-4, IL-5, IL-6 and IL-10. The accelerated shift from the production of extra Th1 cells during these cellular immune activities to more Th2 cells with their predominantly humoral immune functions, caused by such a zinc deficiency, adversely influences the course of diseases such as leprosy, schistosomiasis, leishmaniasis and AIDS, and can result in allergies. It is noteworthy that AIDS viruses (HIVs) do not replicate in Th1 cells, which probably contain more zinc, but preferentially in the Th0 and Th2 cells; all the more so, because zinc and copper ions are known to inhibit intracellular HIV replication. Considering the above Th1/Th2 switch, real prospects seem to be offered of vaccination against such parasites as Leishmania and against HIVs.

The somatotropic axis in neonatal calves can be modulated by nutrition, growth hormone, and Long-R3-IGF-I.

Am J Physiol

H Hammon, J W Blum

Effects on the somatotropic axis [plasma levels of insulin-like growth factors (IGFs) I and II, IGF-binding proteins (IGFBPs), and growth hormone (GH)] of feeding different amounts of colostrum or milk replacer, of Long-R3-IGF-I (administered subcutaneously or orally; 50 micrograms.kg body wt-1.day-1 for 7 days), and of subcutaneously injected recombinant bovine GH (rbGH; 1 mg.kg body wt-1.day-1 for 7 days) were evaluated in calves during the 1st wk of life. Plasma Long-R3-IGF-I increased after subcutaneous application but not with the oral dose. Endogenous IGF-I was higher in calves fed colostrum six times compared with those fed only milk replacer. Native IGF-I was highest in rbGH-injected calves but was lowered by the subcutaneous injection of Long-R3-IGF-I. IGF-II concentrations were not modified by any of the treatments. IGFBP-2 increased in calves fed only milk replacer and those receiving subcutaneous Long-R3-IGF-I. GH was not modulated by differences in nutrition but increased after rbGH administration and similarly in all groups after intravenous injection of GH-releasing factor analog GRF-(1-29). Parenteral administration of Long-R3-IGF-I decreased GH concentration but did not affect the secretory pattern. The data demonstrate that the somatotrophic axis is basically functioning in neonatal calves and is influenced by nutrition, GH, and Long-R3-IGF-I.

Altered thymic endocrine activity along with impairments of peripheral zinc metabolism and T-lymphocyte populations are associated with myasthenia gravis: a follow-up study.

J Neuroimmunol

F Licastro, E Mocchegiani, N Fabris +6 more

Thymic endocrine activity was assessed by a bioassay to determine the basal activity of thymulin (TH), a zinc dependent hormone, and its in vitro reactivation in two different age groups of patients with myasthenia gravis (MG). Before thymectomy, basal TH plasma levels were increased in patients over the age of 50 years. Plasma zinc levels were increased in all patients, this increment being very high in old patients. One year after thymectomy both TH and zinc plasma levels decreased. While zinc plasma levels were within the normal ranges for their respective ages, TH levels were lower in young and higher in old patients than in age comparable controls. Young patients with MG showed increased CD3,DR positive peripheral T-cells as well as lymphocytes with the CD16,CD56 phenotype. An increment of CD3 positive cells along with CD4 and CD16,CD56 positive cells were found in older patients. Thymectomy partially affected blood lymphocyte representation only in young patients, since CD3,DR T-cells decreased one year after surgery. No significant variations in T-cell representation were found in old patients after thymectomy. Immunosuppression in thymectomized patients did not significantly affected TH and zinc plasma levels. Very high levels of TH and the presence of additional alterations in T-lymphocyte subsets in old patients suggested that differential age related pathogenetic immunological mechanisms might be associated with the disease.

Analysis of galanin and the galanin antagonist M40 on delayed non-matching-to-position performance in rats lesioned with the cholinergic immunotoxin 192 IgG-saporin.

Behav Neurosci

M P McDonald, G L Wenk, J N Crawley

Galanin is a 29-amino-acid neuropeptide that is overexpressed in Alzheimer's disease (AD) and impairs performance on rodent learning and memory tasks. M40, a peptidergic galanin receptor ligand, blocks galanin-induced impairments on delayed non-matching-to-position (DNMTP). The present experiments used the 192IgG-saporin lesion model of AD to evaluate the actions of galanin and M40 on DNMTP when cholinergic transmission was reduced. Hippocampal choline acetyltransferase levels were correlated with DNMTP choice accuracy in lesioned rats. Intracerebroventricular (icv) galanin reduced choice accuracy in both the lesioned and sham groups. M40 alone, either icv or intrahippocampal, did not affect choice accuracy in either group. These results suggest that excess galanin can produce further deficits in DNMTP performance in a lesion model of AD, but blocking endogenous galanin is not sufficient alone to improve performance in lesioned rats.

Nerve growth factor induces galanin gene expression in the rat basal forebrain: implications for the treatment of cholinergic dysfunction.

J Comp Neurol

B Planas, P E Kolb, M A Raskind +1 more

Nerve growth factor (NGF) is a potential treatment for cholinergic dysfunction associated with Alzheimer's disease (AD). In rats, NGF activates gene expression of the acetylcholine synthetic enzyme choline acetyltransferase (ChAT) and prevents age- and lesion-induced degeneration of basal forebrain (BF) cholinergic neurons. Cholinergic neurons in the BF coexpress galanin (GAL), a neuropeptide that has been shown to impair performance on memory tasks possibly through the inhibition of cholinergic memory pathways. NGF up-regulates both ChAT and GAL gene expression in cultured pheochromocytoma cells; however, the effect of chronic in vivo NGF administration on GAL gene expression within the BF has not been studied. We used in situ hybridization and quantitative autoradiography to assess GAL and ChAT gene expression within the BF of adult male rats following chronic intracerebroventricular infusion of NGF or cytochrome c. We now report that, in addition to stimulating ChAT gene expression, NGF strongly up-regulated the GAL gene in the rat cholinergic BF. NGF had no effect on GAL gene expression in other noncholinergic forebrain regions. NGF induction of GAL gene expression in the BF was specific, because gene expression for another neuropeptide, neurotensin, present within noncholinergic BF neurons was unchanged. Our data provide the first evidence that in vivo NGF administration up-regulates GAL gene expression in the cholinergic BF. These results suggest that the concurrent induction of GAL in the BF could limit the ameliorating actions of NGF on cholinergic dysfunction.

Appetite-suppressing effects of urocortin, a CRF-related neuropeptide.

Science

M Spina, E Merlo-Pich, R K Chan +4 more

The neuropeptide corticotropin-releasing factor (CRF) is well known to act on the central nervous system in ways that mimic stress and result in decreases in exploration, increases in sympathetic activity, decreases in parasympathetic outflow, and decreases in appetitive behavior. Urocortin, a neuropeptide related to CRF, binds with high affinity to the CRF2 receptor, is more potent than CRF in suppressing appetite, but is less potent than CRF in producing anxiety-like effects and activation. Doses as low as 10 nanograms injected intracerebroventricularly were effective in decreasing food intake in food-deprived and free-feeding rats. These results suggest that urocortin may be an endogenous CRF-like factor in the brain responsible for the effects of stress on appetite.

Histidine dipeptide levels in exercised and hypertensive rat muscles.

Biochem Soc Trans

H Hong, P Johnson

Minireview. Galanin-acetylcholine interactions: relevance to memory and Alzheimer's disease.

Life Sci

J N Crawley

The neuropeptide, galanin, and its receptors are localized in the cholinergic basal forebrain and its projection areas in mammalian brain. Centrally administered galanin inhibits acetylcholine release in the rat ventral hippocampus, and produces deficits in learning and memory tasks. In Alzheimer's disease, galanin is overexpressed in terminals innervating the nucleus basalis of Meynert cell bodies. Selective galanin receptor antagonists provide a novel approach for increasing cholinergic function, as a potential adjunct to the clinical treatment of dementias.

Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study.

Life Sci

R T Dorr, R Lines, N Levine +4 more

A pilot phase I study was conducted with a cyclic heptapeptide analog of alpha-melanocyte stimulating hormone (alpha-MSH). The lactam-bridged molecule, called Melanotan-II (MT-II), has the structure Ac-Nle4-Asp5-His6-D-Phe7-Arg8-Trp9-Lys10 alpha-MSH4-10-NH2 (MT-II) and has superpotent melanotropic activity in vitro. A single-blind, alternating day (saline or MT-II), placebo-controlled trial was conducted in 3 normal male volunteers at the starting dose of 0.01 mg/kg of MT-II. Subcutaneous injections of MT-II or saline were given daily (Monday-Friday) for 2 consecutive weeks. Two subjects were escalated by 0.005 mg/kg increments to 0.03 mg/kg and one to 0.025 mg/kg. The 0.03 mg/kg dose produced Grade II somnolence and fatigue in one of two subjects (WHO standards). Mild nausea, not requiring antiemetic treatment, was reported at most MT-II dose levels. A stretching and yawning complex appeared to correlate with the onset of spontaneous, penile erections which were intermittently experienced for 1-5 hours after MT-II dosing, depending on the MT-II dose. Two subjects had increased pigmentation in the face, upper body and buttock, as measured by quantitative reflectance and by visual perception 1 week after MT-II dosing ended. These results demonstrate that MT-II has tanning activity in humans given only 5 low doses every other day by subcutaneous injection. The recommended single MT-II dose for future Phase I studies is 0.025 mg/kg/day.

The treatment of zinc deficiency is an immunotherapy.

Int J Immunopharmacol

J W Hadden

Reversibility of the thymic involution and of age-related peripheral immune dysfunctions by zinc supplementation in old mice.

Int J Immunopharmacol

E Mocchegiani, L Santarelli, M Muzzioli +1 more

With advanced ageing the zinc pool undergoes progressive reduction as shown by the low zinc plasma levels and the negative crude zinc balance, both in humans and in rodents. It has been suggested that such zinc deficiency might be involved in many age-related immunological dysfunctions, including thymic failure. The relevance of zinc for good functioning of the entire immune system is, at present, well documented. In particular, zinc is required to confer biological activity to one of the best-known thymic peptides, thymulin, which is responsible for cell-mediated immunity. In deep zinc deficiencies, in humans and other animals, the low thymulin levels are due not to a primary failure of the thymus, but to a reduced peripheral saturation of thymic hormones by zinc ions. In aged mice both a reduced peripheral saturation of the hormone and a decreased production by the thymus were present. Oral zinc supplementation in old mice (22 months old) for 1 month induced a complete recovery of crude zinc balance from negative (-1.82) to positive values (+1.47), similar to those of young animals (+1.67). A full recovery of thymic functions with a regrowth of the organ and a partial restoration of the peripheral immune efficiency, as measured by mitogen responsiveness (PHA and ConA) and natural killer cell (NK) activity, were observed after zinc supplementation. These findings clearly pin-point for relevance of zinc for immune efficiency and suggest that the age-related thymic involution and peripheral immunological dysfunctions are not intrinsic and irreversible events but are largely dependent on the altered zinc pool.