Cytokine responsiveness in germfree and conventional NMRI mice

Transgenerational epigenetic effects on innate immunity in broilers: an underestimated field to be explored?

Transgenerational epigenetics is becoming more and more important for understanding the variation of physiological responses of individuals to the environment and the inheritance of these responses based on all mechanisms other than the actual DNA nucleotide sequence. Transgenerational epigenetics is the phenomenon that the information of the environment of (usually) a female animal is translated into memory-like responses preparing the offspring. As a consequence, individuals of the next generation may show different phenotypic traits depending whether their mothers were kept under different environmental conditions. This may result in either positive or negative effects on the next-generation individuals, which is different from individuals from mothers that have been kept in a different environment. Transgenerational epigenetic effects have been proposed and indicated for specific immune (T cell and antibody) responses (especially in mammals, but also in birds) and innate immunity (nonvertebrates), but surprisingly very little is known of transgenerational effects on innate immunity in chickens. Given the short lifespan of the chicken and therefore the likely dependence of chicken on innate immune mechanisms, more attention should be given to this arm of immunity and mechanisms of inheritance including transgenerational effects that can be initiated in the breeder generation. In addition, it is becoming evident that innate immunity also underlies metabolic disorders in broilers. In the current paper, we will argue that although very little is known of transgenerational effects of innate immunity in poultry, more attention should be given to this type of study. We will illustrate examples of transgenerational epigenetics, and finally propose strategies that should reveal the presence of transgenerational epigenetic effects on innate immunity in chickens and strategies to modulate breeder birds such that these effects positively affect innate immunity of broilers. It is suggested that a mismatch between breeder environment and broiler environment may account for unwanted effects of innate immunity in the broiler.

Inflammatory networks in the control of spermatogenesis : chronic inflammation in an immunologically privileged tissue?

Spermatogenesis is a complex, organized process involving intimate interactions between the developing germ cells and supporting Sertoli cells. The process is also highly regulated. Studies suggest that regulation in the seminiferous epithelium involves molecules normally associated with either immune or inflammatory processes; in particular, interleukin 1a (IL1a), IL6, tumor necrosis factor (TNFa), activin A and nitric oxide (NO). While there is considerable evidence that these inflammatory mediators have effects on spermatogonial and spermatocyte development as well as critical supportive functions of the Sertoli cells, which are undoubtedly of considerable importance during testicular inflammation, there remains some skepticism regarding the significance of these molecules with respect to normal testicular function. Nonetheless, it is evident that expression of these regulators varies across the cycle of the seminiferous epithelium in a consistent manner, with major changes in production coinciding with key events within the cycle. This review summarizes the evidence supporting the hypothesis that inflammatory cytokines play a role in normal testicular spermatogenesis, as well as in the etiology of inflammation induced sub-fertility. The balance of data leads to the striking conclusion that the cycle of the seminiferous epithelium resembles a chronic inflammatory event. This appears to be a somewhat paradoxical assertion, since the testis is an immunologically privileged tissue based on its well-established ability to support grafts with minimal rejection responses. However, it may be argued that local immunoregulatory mechanisms, which confer protection from immunity on both transplanted tissues and the developing spermatogenic cells, are equally necessary to prevent local inflammation responses associated with the spermatogenic process from activating the adaptive immune response.

Single subcutaneous administration of chorionic gonadotropin to rats induces a rapid and transient increase in testicular expression of pro-inflammatory cytokines

hCG has been reported to cause an inflammation-like effect in the testis, although the background and consequences of this phenomenon remain to be understood. This investigation reveals that a single injection of hCG (100 U) induces a transient surge in pro-inflammatory cytokine expression in the adult rat testis. Reverse transcriptase PCR analysis demonstrated onset of testicular expression of IL-1beta and IL-6 mRNA and increases in the levels of mRNA encoding the constitutively expressed cytokines IL-1alpha, IL-1 receptor antagonist, and tumor necrosis factor-alpha 4 h after hCG injection and a maximal response after 8-12 h. These increases were accompanied by a transient increase in testicular IL-1 bioactive protein. Twenty-four hours after administration of hCG, the levels of all cytokine mRNA had decreased, although most were still elevated above control. Immunohistochemical staining revealed that the IL-1beta protein was undetectable in normal testes but was seen to be localized to interstitial macrophages but not Leydig cells after hCG treatment. Testes devoid of Leydig cells after pretreatment with ethane dimethane sulphonate exhibited normal staining for interstitial macrophages but failed to respond to hCG with increases in IL-1beta mRNA and protein expression. We conclude that hCG induces testicular inflammation via local activation by Leydig cells of the production of pro-inflammatory cytokines by resident macrophages. It remains to be investigated whether the high-dose hCG regimens used for treatment of boys with cryptorchidism could induce similar increases of pro-inflammatory cytokines in the human testis and if such treatments could adversely affect future testicular function.

Production and secretion of interleukin-1alpha proteins by rat testis

The present study characterizes constitutively expressed rat testicular interleukin-1alpha (IL-1alpha) proteins. IL-1 bioactivity of crude testis protein was completely neutralized by IL-1alpha antiserum, IL-1 receptor antagonist, and soluble type I IL-1 receptor. Upon non-denaturating gel permeation chromatography, bioactive IL-1 eluted at molecular sizes of 45, 31, and 17kDa and at charges of pH 5.7 and 6.0 after chromatofocusing. SDS-PAGE/Western blot analysis of proteins extracted from whole testis, seminiferous tubules, interstitial, and seminiferous tubule fluids all demonstrated IL-1alpha immunoreactivity at 45, 24, and 19kDa. Activated macrophages and tissue proteins from endotoxin treated rats showed immunoreactive 31 and 19kDa IL-1alpha. The results indicate that the testis produces three isoforms of IL-1alpha proteins that are secreted into the interstitial compartment and tubular lumen where they may exert paracrine functions. The testicular IL-1alpha isoforms may represent posttranslationally modified precursor, mature IL-1alpha, and a 24-kDa alternate splice form.

Endotoxin-induced interleukin 1 expression in testicular macrophages is accompanied by downregulation of the constitutive expression in Sertoli cells

Interleukin-1alpha (IL-1alpha) is constitutively produced by Sertoli cells in adult rat testes. We demonstrate here that adult rats initiate expression of IL-1alpha and IL-1beta in testicular macrophages and decrease plasma testosterone by 60%, 2 h after administration of endotoxin. The macrophage activation was accompanied by downregulation of IL-1alpha mRNA expression in Sertoli cells. Despite increased tissue concentrations of IL-1alpha and IL-1beta immunoreactive protein, the level of bioactive IL-1 in the testis remained unchanged. Testes from prepubertal rats responded similarly to endotoxin, but lacked constitutive expression of IL-1alpha. We conclude that endotoxin-induced inflammation involves the testis by local macrophage activation and cytokine secretion. The paracrine mechanisms regulating IL-1 bioactivity in the testis are unknown but may represent a means to protect germ cells from noxious effects of inflammation.

Constitutive production of interleukin-1alpha mRNA and protein in the developing rat testis

Interleukin-1 (IL-1), a multifunctional cytokine produced mainly by activated macrophages, is also produced in the intact testis. Rat testicular IL-1 was found to be identical to IL-1alpha, judged by immunoneutralization of the bioactive protein and sequence comparison of cloned rat testicular and macrophage pro-IL-1alpha cDNA. Testicular IL-1alpha mRNA was first demonstrated on postnatal day 15, and the corresponding bioactive protein from day 20. IL-1alpha mRNA was still low on day 20, but then increased rapidly in parallel with the bioactive protein to establish a plateau level from day 25. In adult testes, IL-1alpha mRNA and immunoreactive protein were low in stage VII of the seminiferous epithelial cycle, whereas other stages showed a clearly detectable expression. In the adult testis, the concentration of IL-1alpha was 75 pg/mg testicular protein (approximately 200 pM). In conclusion, production of testicular IL-1alpha is developmentally and stage-dependently regulated, probably at the transcriptional level, emphasizing an important paracrine role in testicular function.

Molecular cloning and expression of a functionally different alternative splice variant of prointerleukin-1alpha from the rat testis

We report here the characterization of an alternative splice variant of prointerleukin-1alpha (proIL-1alpha), constitutively expressed by the normal adult rat testis. In addition to the classical 32K proIL-1alpha (32proIL-1alpha) messenger RNA, the testis produced a shorter variant encoding a putative protein of 24K (24proIL-1alpha). In situ hybridization demonstrated constitutive expression of the splice transcript in the seminiferous tubules. This alternative complementary DNA lacked the fifth exon, harboring the calpain cleavage site essential for generation of mature 17K IL-1alpha. This was verified by calpain treatment, producing the expected cleavage products of recombinant 32proIL-1alpha, but not of 24proIL-1alpha. Similarly, expression in COS-7 cells demonstrated processing of 32proIL-1alpha to the mature 17K form and secretion, whereas 24proIL-1alpha remained unprocessed. Both 32proIL-1alpha and 24proIL-1alpha showed a dose-dependent stimulatory effect in a thymocyte proliferation assay, although at lower potency than mature 17K IL-1alpha. In contrast, when tested on hCG-stimulated Leydig cells in vitro, a dose-dependent inhibition of testosterone production was obtained with mature 17K IL-1alpha and at a lower potency with 32proIL-1alpha, whereas 24proIL-1alpha was inactive. In conclusion, the three IL-1 bioactive proteins described here contribute to IL-1 protein heterogeneity and may serve as constitutive paracrine mediators in the testis.

Constitutive expression of interleukin-1alpha messenger ribonucleic acid in rat Sertoli cells is dependent upon interaction with germ cells

Interleukin-1 (IL-1), a proinflammatory cytokine originally isolated as a product of activated mononuclear phagocytes, consists of two distinct agonist proteins, IL-1alpha and IL-1beta, of which IL-1beta is the major inducible IL-1 protein produced by macrophages. We show here that mRNA of IL-1alpha, but not IL-1beta, is constitutively expressed by the intact rat testis and localize the transcript to Sertoli cells as confirmed by a novel squash technique. The expression is developmentally regulated and appears only after postnatal day 20 in the rat testis, corresponding to onset of puberty. IL-1alpha mRNA shows a stage-dependent expression pattern during the cycle of the seminiferous epithelium. It is low or absent in stage VII, but present in all other stages of the cycle. The same stage-dependent distribution was also observed at the protein level when bioactive IL-1 was measured in extracts of accurately defined one millimeter segments of seminiferous tubules. No IL-1alpha mRNA was detected in adult rat testes after germ cell depletion by fetal irradiation or cytostatic drug treatment. Because stage VII is the only segment of the seminiferous tubules lacking DNA replication, we propose that IL-1alpha is involved in this event during mitosis and meiosis of spermatogenesis and that its expression is dependent upon interactions between Sertoli cells and germ cells.

Stage-specific regulation of stem cell factor gene expression in the rat seminiferous epithelium

To assess the regulation of stem factor factor (SCF) gene expression during spermatogenesis, we tested the effects of hormones (FSH, testosterone, and 17beta-estradiol) and some growth factors [transforming growth factor-beta (TGF beta), TGF alpha, tumor necrosis factor-alpha, and activin] on SCF gene expression by using a transillumination-assisted microdisection technique, a seminiferous tubule culture system, and Northern hybridization. Our results showed that FSH (10 ng/ml) increased steady state levels of SCF messenger RNA (mRNA) in a stage-specific and time-dependent manner. 8-Bromo-cAMP could increase the SCF mRNA level in a similar way as FSH, whereas phorbol 12-myristate 13-acetate had no effect. Actinomycin D could abolish the stimulatory effect of FSH, whereas cyclohexamide could not. The half-life of SCF mRNA was apparently prolonged after FSH stimulation (FSH-treated tubules, 15.6 +/- 1.2 h; controls, 8.6 +/- 2.7 h). Nuclear run-on assay revealed 5- and 10-fold increases in the transcription rate after FSH stimulation for 8 and 30 h, respectively. Neither testosterone nor estradiol had significant effects on SCF gene expression in our tissue culture system. Activin, TGF beta, TGF alpha, and tumor necrosis factor-alpha had no effect on SCF gene expression in vitro. In conclusion, SCF gene expression in the rat seminiferous tubule is regulated by FSH through the cAMP/protein kinase A pathway. FSH regulates SCF gene expression at both transcriptional and posttranscriptional levels involving the increase in transcription rate and prolongation of half-life of SCF mRNA, but is independent of de novo protein synthesis.

Enhanced expression of interleukin (IL)-1 and IL-6 messenger RNA and bioactive protein after hypoxia-ischemia in neonatal rats

The effect of hypoxia-ischemia (HI) on IL-1, and IL-6 bioactivity in relation to expression of IL-1 alpha, IL-1 beta, and IL-6 mRNA was studied, and the neuroprotective efficacy of IL-1 receptor antagonist (IL-1ra) was evaluated in neonatal rats. HI was induced in 7-d-old rats by unilateral carotid artery ligation and hypoxia for 70-100 min. Animals were killed at different time points up to 14 d after HI, and brains were analyzed for IL-1 and IL-6 bioactivity using bioassays and for mRNA for IL-1 alpha, IL-1 beta, and IL-6 with reverse transcription followed by a polymerase chain reaction. In separate animals, IL-1ra was administered intracerebrally before or after HI, and the extent of brain injury was assessed 14 d after HI. A transient increase of IL-1 bioactivity occurred after HI, reaching a peak at 6 h of recovery. IL-1 beta mRNA followed a similar time course but attained maximum expression at 3 h. IL-6 bioactivity and mRNA were also stimulated by HI and followed a similar time course as IL-1. Pretreatment with IL-1ra reduced HI brain damage from 54.4 +/- 9.3 to 41.4 +/- 10.0% (p < or = 0.01), and IL-1ra posttreatment increased the proportion of animals devoid of brain injury (40%) compared with vehicle-treated controls (13%) (p < or = 0.05). In conclusion, a transient activation of IL-1 and IL-6 occurred after HI, and IL-1ra reduced HI brain injury to a moderate degree.

A model of host-microbial interactions in an open mammalian ecosystem

The maintenance and significance of the complex populations of microbes present in the mammalian intestine are poorly understood. Comparison of conventionally housed and germ-free NMRI mice revealed that production of fucosylated glycoconjugates and an alpha1, 2-fucosyltransferase messenger RNA in the small-intestinal epithelium requires the normal microflora. Colonization of germ-free mice with Bacteroides thetaiotaomicron, a component of this flora, restored the fucosylation program, whereas an isogenic strain carrying a transposon insertion that disrupts its ability to use L-fucose as a carbon source did not. Simplified models such as this should aid the study of open microbial ecosystems.

Elevated circulating levels of interleukin-1 receptor antagonist but not IL-1 agonists in hemophagocytic lymphohistiocytosis

The familial form of hemophagocytic lymphohistiocytosis (HLH) is an inherited disease with disturbed immunomodulation and characterized by fever, hepatosplenomegaly, cytopenia, hypertriglyceridemia, and coagulopathy, i.e., findings which are similar to many of the reported biological effects of the inflammatory cytokines. Due to the previously shown hypercytokinemia in active HLH with elevated levels of interleukin (IL)-6, tumor necrosis factor-alpha, and interferon-gamma, it has been suggested that cytokine dysregulation may be of pathophysiological importance. Here we have assayed the serum levels of the members of the IL-1 ligand family, the two agonists IL-1 alpha and IL-1 beta and the antagonist IL-1 receptor antagonist (IL-1ra), in nine children with HLH and cerebrospinal fluid (CSF) specimens from four children. Serum IL-1ra was elevated in all patients with active disease to a degree which correlated well with disease activity. Furthermore, the levels decreased day by day during treatment of a patient who suffered a relapse. Moreover, high levels of IL-1ra were also detected in CSF during active disease. However, IL-1 beta levels were all within normal limits and circulating IL-1 alpha levels were normal in all but two patients.

Mercury induces in vivo and in vitro secretion of interleukin-1 in mice

Macrophages from SJL and DBA mice incubated with mercuric chloride (HgCl2) in vitro for 24-72 h secreted an increased amount of interleukin 1 (IL-1) to the supernatant compared with control-incubated macrophages, as determined by a sensitive thymocyte proliferation assay. The increase of IL-1 activity showed a highly significant dose-response relationship, being close to that in controls at 10(-8) M, and maximal after incubation with 10(-5)-10(-6) M HgCl2 in both strains. At optimal concentrations of HgCl2 the IL-1 activity started to increase after 6 hrs incubation and reached a maximum after 48 h. Incubation with concentrations of HgCl2 higher than 10(-5) M resulted in a severely reduced IL-1 activity, which correlated with a reduced cell viability. Extracts of HgCl2-incubated macrophages representing cell-bound IL-1 showed no increase in IL-1 activity, irrespective of the concentration or incubation time. Topical application of HgCl2 in a mixture of acetone-olive oil on the external ear of SJL mice induced a dose- and time-dependent increase in IL-1 activity. A maximal increase was seen after application of 1% HgCl2 for 24 h with lower IL-1 activity after 48 and 72 h. Application of 5%, but not 1% or 0.1%, slightly increased the IL-1 activity in the contralateral ear treated with acetone-olive oil only, as compared with the activity in ears from animals given no mercury treatment, suggesting a systemic effect by application of 5% HgCl2.(ABSTRACT TRUNCATED AT 250 WORDS)

Paneth cell differentiation in the developing intestine of normal and transgenic mice

Paneth cells represent one of the four major epithelial lineages in the mouse small intestine. It is the only lineage that migrates downward from the stem-cell zone located in the lower portion of the crypt of Lieberkühn to the crypt base. Mature Paneth cells release growth factors, digestive enzymes, and antimicrobial peptides from their apical secretory granules. Some of these factors may affect the crypt stem cell, its transit-cell descendants, differentiating villus-associated epithelial lineages, and/or the gut microflora. We used single and multilabel immunocytochemical methods to study Paneth cell differentiation during and after completion of gut morphogenesis in normal, gnotobiotic, and transgenic mice as well as in intestinal isografts. This lineage emerges coincident with cytodifferentiation of the fetal small intestinal endoderm, formation of crypts from an intervillus epithelium, and establishment of a stem-cell hierarchy. The initial differentiation program involves sequential expression of cryptdins, a phospholipase A2 (enhancing factor), and lysozyme. A dramatic increase in Paneth cell number per crypt occurs during postnatal days 14-28, when crypts proliferate by fission. Accumulation of fucosylated and sialylated glycoconjugates during this period represents the final evolution of the lineage's differentiation program. Establishment of this lineage is not dependent upon instructive interactions from the microflora. Transgenic mice containing nucleotides -6500 to +34 of the Paneth cell-specific mouse cryptdin 2 gene linked to the human growth hormone gene beginning at its nucleotide +3 inappropriately express human growth hormone in a large population of proliferating and nonproliferating cells in the intervillus epithelium up to postnatal day 5. Transgene expression subsequently becomes restricted to the Paneth cell lineage in the developing crypt. Cryptdin 2 nucleotides -6500 to +34 should be a useful marker of crypt morphogenesis and a valuable tool for conducting gain-of-function or loss-of-function experiments in Paneth cells.

Role of transforming growth factor beta in testicular immunosuppression

The potential role of transforming growth factor beta (TGF beta) in the regulation of the immunological milieu of the testis was investigated. Antibodies neutralizing TGF beta reversed the previously observed suppression of rat peripheral blood lymphocyte proliferation induced by rat abdominal testis extract. Recombinant TGF beta 1 dose-dependently inhibited testicular interleukin-1-like factor-driven proliferation of murine thymocytes and ConA-stimulated rat peripheral blood mononuclear cells. Extracts of seminiferous tubules contained a M(r) approximately 25 K TGF beta-like growth inhibitor of the CLL-64 mink lung epithelial cell line. The present findings suggest an important role for TGF beta in testicular immunosuppression.