Processing of interleukin-1 in cells of monocytic lineage is differentiation-dependent

The precursor but not the mature form of IL1alpha blocks the release of FGF1 in response to heat shock

Interleukin (IL)1alpha mediates proinflammatory events through its extracellular interaction with the IL1 type I receptor. However, IL1alpha does not contain a conventional signal peptide sequence that provides access to the endoplasmic reticulum-Golgi apparatus for secretion. Thus, we have studied the release of the precursor (p) and mature (m) forms of IL1alpha from NIH 3T3 cells. We have demonstrated that mIL1alpha but not pIL1alpha was released in response to heat shock with biochemical and pharmacological properties similar to those reported for the stress-mediated release pathway utilized by fibroblast growth factor (FGF)1. However, unlike the FGF1 release pathway, the IL1alpha release pathway appears to function independently of synaptotagmin (Syt)1 because the expression of a dominant-negative form of Syt1, which represses the release of FGF1, did not inhibit the release of mIL1alpha in response to temperature stress. Interestingly, whereas the expression of both mIL1alpha and FGF1 in NIH 3T3 cells did not impair the stress-induced release of either polypeptide, the expression of both pIL1alpha and FGF1 repressed the release of FGF1 in response to temperature stress. These data suggest that the release of mIL1alpha requires proteolytic processing of its precursor form and that mIL1alpha and FGF1 may utilize similar but distinct mechanisms for export.

Production of interleukin-1-like molecules by human sperm cells

OBJECTIVE

To characterize and localize interleukin (IL)-1alpha and IL-1beta in human sperm cells.

DESIGN

Prospective and comparative study.

SETTING

Andrology clinic of a university hospital.

PATIENT(S)

Two groups of normogonadotropic men: 17 fertile men (donors with proved fertility) and 8 oligoteratoasthenospermic infertile men.

INTERVENTION(S)

None. MAIN OTUCOME MEASURE(s): Evaluation of IL-1alpha and IL-1beta levels and expression in sperm cells by immunohistochemical staining, immunoassay, and Western blot analysis.

RESULT(S)

Both types of IL-1-like molecules (IL-1alpha and IL-1beta) were expressed in the tail, neck, and head of sperm cells of fertile men and patients with oligoteratoasthenospermia. Swim-up sperm cells from fertile men and patients with oligoteratoasthenospermia secreted similar levels of IL-1-like molecules. The levels of IL-1beta-like molecules were higher than those of IL-1alpha-like molecules in both groups. The expressed IL-1-like molecules were characterized by the presence a 60-kd protein for both IL-1alpha-like and IL-1beta-like molecules. In some samples of both fertile men and infertile men with oligoteratoasthenospermia, 17-kd, 33-kd, and 45-kd IL-1beta-like molecules were detected. Impairment of sperm function, such as decreased sperm count and motility and/or impaired morphology, was not related to the capacity of sperm cells to produce IL-1-like molecules.

CONCLUSION(S)

IL-1 molecules originating in sperm cells may play a role in the physiologic functions of sperm cells (autocrine effect) and/or in cell-cell interactions within the testis (paracrine effect).

Time dependent production of cytokines and eicosanoids by human monocytic leukaemia U937 cells; effects of glucocorticosteroids

In the present study the human monoblast cell line U937 has been used as a model to study the function of human mononuclear phagocytes in asthma. The kinetics of the production of eicosanoids and cytokines, which are thought to play a role in the pathogenesis of asthma, were studied. In addition, the effects of glucocorticosteroids were investigated, as these drugs are of great importance for the treatment of asthmatic patients. After stimulation with phorbol-12 myristate acetate (PMA) for 24 h, U937 cells were cultured in the absence or presence of lipopolysaccharide (LPS: 1 and 5 microg ml(-1)) and glucocorticosteroids (budesonide, fluticasone propionate and prednisolone: 10(-11), 10(-9) and 10(-7) M) for 96 h. The production of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), prostaglandin E2 (PGE2) and thromboxane B2 (TxB2) gradually increased in time after stimulation with LPS, whereas the transient production of tumor necrosis factor alpha (TNF-alpha) reached its maximum between 6 and 12 h. Interferon-gamma (IFN-gamma), interleukin-10 (IL-10) and leukotriene B4 (LTB4) were not detectable. All three glucocorticosteroids (budesonide, fluticasone propionate and prednisolone) completely inhibited the production of both eicosanoids and cytokines. The production of eicosanoids was more sensitive to these glucocorticoids than the production of cytokines. The observed differences in the kinetics of the production of eicosanoids and cytokines stress the importance of time course experiments in studies on the effect of drugs on mononuclear cells.

In vitro cytokine secretion and maturation phenotype of lymphoma-associated splenic macrophages

In this study, cytokine secretion capacity and maturation phenotype of human lymphoma-associated splenic macrophages (LASM) were evaluated in a long-term culture. Sixteen spleens from malignant lymphoma patients and five control spleens were investigated. Splenic macrophages (SM) were isolated by teflon adherence and cultured for 6-48 days. Secretion of IL-1 alpha, IL-6 and TNF alpha was measured by ELISA following maximal stimulation with LPS and IFN-gamma, and cytokine mRNA expression was detected by in situ hybridization. Immunohistochemical expression of maturation-associated antigens was evaluated semiquantitatively. Cytokine secretion capacity was significantly altered in LASM which exhibited reduced TNF alpha and IL-6, but elevated IL-1 alpha secretion when compared to control SM. Alterations of cytokine secretion capacity were associated with a modification of LASM maturation phenotype, showing impaired expression of early and chronic/late inflammatory markers. These findings obtained from a long-term culture model suggest that malignant lymphomas induce lasting modifications of cytokine secretion and maturation patterns in LASM.

The mature form of interleukin-1 alpha is constitutively expressed in immature male germ cells from rat

In the present study we show that immature germ cells from rat testis contain both interleukin-1 alpha (IL-1 alpha) mRNA and immunoreactive proteins. In contrast, in primary cultures of Sertoli cells and peritubular cells. IL-1 alpha mRNA and immunoreactive protein were below the levels of detection. Immunoblots of lysates from these germ cells showed the presence of strong 17 kDa bands (mature forms of IL-1 alpha) and a much weaker 33 kDa band (precursor form). The finding of cell-associated mature forms of IL-1 alpha in germ cells indicates that immature male germ cells are able to process IL-1 alpha independent of its secretion. Data from isolated cell fractions, as well as from whole testis tissue from rats of various ages, indicate that IL-1 alpha expression takes place in late pachytene spermatocytes and early round spermatids. Whether IL-1 alpha plays a role intracellularly in germ cells or exerts its effects on neighboring Sertoli cells remains to be shown.

Interleukin 1 beta propeptide is detected intracellularly and extracellularly when human monocytes are stimulated with LPS in vitro

Human interleukin 1 beta (IL-1 beta) is synthesized as an inactive precursor that is cleaved by IL-1 converting enzyme (ICE) between Asp116 and Ala117 to form COOH-terminal mature IL-1 beta and NH2-terminal IL-1 beta propeptide. Little is known about the fate of the NH2-terminal cleavage product. In this study, human recombinant (hr)IL-1 beta propeptide (amino acids 2-116) was produced and used to prepare specific antibodies which do not recognize mature human IL-1 beta. These anti-propeptide antibodies were used for immunoprecipitation of biosynthetically labeled proteins from lipopolysaccharide-stimulated human monocytes. Analysis of immunoprecipitates by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography revealed that these antibodies recognize precursor IL-1 beta and two unique proteins: one migrating at 17.5 kD and one at 14 kD. The larger of these two proteins has a migration nearly identical to that of the recombinant IL-1 beta propeptide, and most likely represents naturally derived propeptide. The protein migrating at 14 kD may result from a second cleavage by ICE, between Asp27 and Gly28. These proteins accumulate intracellularly and extracellularly during pulse-chase experiments, and therefore represent stable products of precursor IL-1 beta cleavage.

Differentiation-stage specific self-peptides bound by major histocompatibility complex class I molecules

We have tested the hypothesis that phenotypic changes of development are accompanied by expression of differentiation-stage specific peptides bound to major histocompatibility complex (MHC) class I molecules. The U937 cell line, when cultured in the presence of phorbol myristate acetate (PMA), undergoes differentiation from monoblasts to macrophage-like cells. The high-performance liquid chromatography profile of peptides eluted from purified human histocompatibility leukocyte antigen class I molecules expressed by U937 treated with PMA differs from that obtained from control, untreated U937 cells. Chemical sequencing of eluted peptides identified a peptide derived from cytomegalovirus in both treated and untreated cells. PMA-treated, but not untreated cells, displayed an additional peptide derived from interleukin 1 beta. Hence, differentiation-induction of U937 is accompanied by the presentation of at least one differentiation-stage specific peptide. Our results indicate that, similar to viral infection, cellular development and transformation is accompanied by the de novo synthesis of proteins which are processed and presented on MHC class I molecules.