Differential effects of in vitro mycoplasma infection on interleukin-1 alpha and beta mRNA expression in U937 and A431 cells

Fetal bovine serum, an important factor affecting the reproducibility of cell experiments

Fetal bovine serum (FBS) is a natural medium used in cell cultures containing the large amount of nutrients necessary for cell growth and is often used for in vitro cultures of animal cells. Although FBS plays a vital role in cell cultures, there are small molecules contained within FBS that remain unidentified, and their effects on cultured cells is poorly understood. Here, we report that different brands of FBS have varying influences on the background expression of IL-8, not TNFα and IL1β in epithelial cells. The endogenous small molecules in FBS and ERK pathways may contribute to these effects. In addition, FBS form the IL-8 stimulation and IL-8 non-responsive groups have different metabolome profiles. Overall, our study suggests that metabolites in FBS should be included in the quantitative considerations when conducting cell experiments, especially immune-related experiments, to improve the repeatability of experimental results in scientific papers; IL-8 could thus be an important factor in selecting FBS.

Chlamydia trachomatis growth stimulates interleukin 8 production by human monocytic U-937 cells

Growth of Chlamydia trachomatis serotypes L2 and L3 in a human monocytic cell line, U-937, increased the rate of interleukin 8 (IL-8) release 100-fold. Heat-killed chlamydiae induced a 10-fold-lower level of production of IL-8. IL-8 may play an important role in the inflammatory reaction to chlamydial infection.

Mycoplasma arginini TUH-14 membrane lipoproteins induce production of interleukin-1, interleukin-6, and tumor necrosis factor alpha by human monocytes

Mycoplasma arginini TUH-14 partially purified membrane lipoproteins (TUH-14-pp) directly induce secretion of the cytokines involved in the inflammatory response, namely, interleukin 1 (IL-1), tumor necrosis factor alpha, and IL-6, by human monocytes cultured in the absence of serum. The biological activity of each cytokine correlates with its immunoreactivity. Upon stimulation with either TUH-14-pp or lipopolysaccharide, most tumor necrosis factor alpha and IL-6 is secreted in the extracellular compartment, whereas a significant amount of IL-1 remains cell associated. Finally, polymyxin B does not affect secretion of cytokines induced by TUH-14-pp, indicating that mycoplasma lipopolysaccharide does not account for their effects on monocytes. Altogether, our data show that direct interaction of mycoplasma membrane components with human blood monocytes induces secretion of high levels of cytokines known to trigger inflammatory responses. This new concept of membrane-bound active components of mycoplasma may explain its ability to efficiently initiate inflammatory reactions.

Increased levels of tumor necrosis factor and interleukin 1 in bronchoalveolar lavage fluids from pigs infected with Mycoplasma hyopneumoniae

We examined the levels of tumor necrosis factor (TNF)-alpha and interleukin-1 (IL-1) in bronchoalveolar lavage fluids (BALF) from pigs experimentally infected with Mycoplasma hyopneumoniae using biological assays with WEHI-164 cells and D10.G4.1 cells, respectively. Increased TNF-alpha and IL-1 in BALF were found in infected pigs with gross and/or microscopic lesions. A time-course study suggested TNF-alpha and IL-1 to be persistently elevated in infected pigs. Their presence in BALF would thus appear to be associated with the development of pneumonic lesions in M. hyopneumoniae infected pigs.

No direct neuronotoxicity by HIV-1 virions or culture fluids from HIV-1-infected T cells or monocytes

Macrophages and microglia are the principal target cells for human immunodeficiency virus (HIV) in brain, and as such, are likely participants in the neuropathology of HIV infection. In a model system for this process, we found that fluids from human monocyte cultures enhanced survival and differentiation of the neurons in fetal rat brain explants. In contrast, fluids from HIV-infected monocyte cultures were strongly toxic to neurons and paradoxically enhanced the proliferation of glial cells. Further, neuronotoxic activity in these fluids was mediated through activation of NMDA binding receptors on the neurons and was inhibited by any of several different NMDA antagonists. Neuronotoxic activity was directly related to contamination of the HIV virus stock with Mycoplasma arginini and M. hominis. Pure cultures of mycoplasma, bacterial lipopolysaccharide (LPS), or murine recombinant tumor necrosis factor alpha (rTNF alpha) each induced neuronotoxicity which exactly mirrored that induced by the contaminated HIV stock. It is likely that mycoplasma or components of the mycoplasma plasma membrane stimulate TNF alpha production by the glial cells in the brain explants. Indeed, careful depletion of glial cells in these explants prevented mycoplasma or LPS-mediated neuronotoxicity. No neuronotoxicity was evident with HIV-1 virus stock, HIV-1 gp120, or culture fluids from HIV-infected T cells or monocytes when these preparations were free of contamination by mycoplasma and LPS. These findings suggest caution in interpretation of those experiments in which similar contamination has not been rigorously excluded.

Interleukin 1 receptor antagonist in human epidermis and cultured keratinocytes

Interleukin 1 (IL-1), present in high amounts in normal human skin without any sign of inflammation, suggests a complex mechanism by which its bioactivity is regulated. The specific receptor antagonist of IL-1 (IL-1ra) was analyzed in human skin, sweat and cultured keratinocytes. Extracts of both skin and cultured keratinocytes blocked the binding of [125I]IL-1 to its receptor whereas sweat did not. The inhibitory activity was cell-associated, was not secreted by cultured keratinocytes, and IL-1ra mRNA was identified in these cells. There was an inverse relationship between the level of IL-1ra and that of IL-1 alpha and beta since extracts of differentiating keratinocytes (DK) and higher IL-1ra levels and expressed more mRNA for IL-1ra than non-differentiated keratinocytes (NDK), whereas NDK contained 4 times more IL-1 alpha and beta proteins than DK. This association of cell differentiation with a shift in agonist/antagonist ratio might be related to important autocrine or paracrine functions of IL-1 in normal and inflamed human skin.

IL1/ETAF activity and undetectable IL1 beta mRNA and minimal IL1 alpha mRNA levels in normal adult heat-separated epidermis

Interleukin 1 (IL 1), a cytokine expressed from a number of cell types, plays a vital part in immune and inflammatory processes. Epidermal IL1-like activity, also known as epidermal cell thymocyte-activating factor (ETAF), is associated with whole skin, epidermis, Langerhans cells and cultured keratinocytes and keratinocyte cell lines. We show that preparations of heat-separated epidermis possess abundant IL1/ETAF activity as indicated by PGE/collagenase induction in cultured synovial cells and proliferation of mouse thymocytes. However, using cDNA probes to interleukin-1 alpha and beta we show that freshly isolated heat-separated epidermis from healthy adult donors contains only a slight detectable level of IL1 alpha mRNA by dot blot analysis and no IL1 beta and IL1 alpha mRNA by Northern blot analysis. The implications of these observations will be discussed.