Interleukin-1 (IL-1) describes two inflammatory proteins, IL-1 alpha and IL-1 beta, produced by activated macrophages and other cell types and encoded by two genes. Their amino acid sequences have only 26% similarity, but their biological activities are comparable, with a few exceptions; indeed, both molecules appear to act at the same receptor. As IL-1 release prostaglandins which sensitize nociceptors in man and in experimental animals, we tested IL-1 alpha and IL-1 beta in rats for hyperalgesic (nociceptive) activity. Our results show that IL-1 beta given systemically is an extremely potent hyperalgesic agent with a probable peripheral site of action; IL-1 alpha is approximately 3,000 times less active than IL-1 beta. We have delineated the region of IL-1 beta mediating the hyperalgesic effect and developed an analgesic tripeptide analogue of IL-1 beta which antagonizes hyperalgesia evoked by IL-1 beta and by the inflammatory agent carrageenan.

The CD28-specific mAb TGN1412 rapidly caused a life-threatening “cytokine storm” in all six healthy volunteers in the Phase I clinical trial of this superagonist, signaling a failure of preclinical safety testing. We report novel in vitro procedures in which TGN1412, immobilized in various ways, is presented to human white blood cells in a manner that stimulates the striking release of cytokines and profound lymphocyte proliferation that occurred in vivo in humans. The novel procedures would have predicted the toxicity of this superagonist and are now being applied to emerging immunotherapeutics and to other therapeutics that have the potential to act upon the immune system. Data from these novel procedures, along with data from in vitro and in vivo studies in nonhuman primates, suggest that the dose of TGN1412 given to human volunteers was close to the maximum immunostimulatory dose and that TGN1412 is not a superagonist in nonhuman primates.

Interleukin-1 beta (IL-1 beta) is thought to act on the brain to induce fever, neuroendocrine activation, and behavioral changes during disease through induction of prostaglandins at the blood-brain barrier (BBB). However, despite the fact that IL-1 beta induces the prostaglandin-synthesizing enzyme cyclooxygenase-2 (COX-2) in brain vascular cells, no study has established the presence of IL-1 receptor type 1 (IL-1R1) protein in these cells. Furthermore, although COX inhibitors attenuate expression of the activation marker c-Fos in the preoptic and paraventricular hypothalamus after administration of IL-1 beta or bacterial lipopolysaccharide (LPS), they do not alter c-Fos induction in other structures known to express prostaglandin receptors. The present study thus sought to establish whether IL-1R1 protein is present and functional in the rat cerebral vasculature. In addition, the distribution of IL-1R1 protein was compared to IL-1 beta- and LPS-induced COX-2 expression. IL-1R1-immunoreactive perivascular cells were mostly found in choroid plexus and meninges. IL-1R1-immunoreactive vessels were seen throughout the brain, but concentrated in the preoptic area, subfornical organ, supraoptic hypothalamus, and to a lesser extent in the paraventricular hypothalamus, cortex, nucleus of the solitary tract, and ventrolateral medulla. Vascular IL-1R1-ir was associated with an endothelial cell marker, not found in arterioles, and corresponded to the induction patterns of phosphorylated c-Jun and inhibitory-factor kappa B mRNA upon IL-1 beta stimulation, and colocalized with peripheral IL-1 beta- or LPS-induced COX-2 expression. These observations indicate that functional IL-1R1s are expressed in endothelial cells of brain venules and suggest that vascular IL-1R1 distribution is an important factor determining BBB prostaglandin-dependent activation of brain structures during infection.

The present study was designed to investigate the coupling mechanisms linking the immune and the neuroendocrine corticotropic systems in an integrated defense response triggered by an infectious aggression. The experimental paradigm used consisted of the exploration in individual conscious rats of the temporal pattern of increased plasma concentrations of the two stress hormones, adrenocorticotropic hormone (ACTH) and corticosterone (Cort), and of three cytokines known as ACTH stimulators, tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1 beta, and IL-6, after intra-arterial infusions of lipopolysaccharide (LPS) given at three doses, 5 micrograms/kg (LPS-5), 25 micrograms/kg (LPS-25), and 1 mg/kg (LPS-1,000). Blood samples were taken 30 min and immediately before LPS injection (t0) and at 15, 30, 60, 120, 300, and 480 min post-LPS. The three doses of LPS induced ACTH and Cort surges, starting after 30 min for LPS-5 and LPS-25 or 15 min for LPS-1,000 and peaking with a similar amplitude at 60 min before receding slowly to baseline at 480 min for the two lower LPS doses. On the other hand, whatever the LPS dose, none of the three cytokines rose above undetectable basal levels before 60 min. They increased thereafter to culminate 10- to 30-fold above baseline at 60 min (TNF-alpha) or 120 min (IL-1 beta and IL-6) after LPS and declined back to basal levels at 300 min (TNF-alpha, all doses, and IL-6 for LPS-5 and LPS-25). After LPS-25, only IL-1 beta had not regressed to baseline levels at 480 min.(ABSTRACT TRUNCATED AT 400 WORDS)

Activated glial cells crucially contribute to brain inflammatory responses. Interleukin-10 (IL-10) is an important modulator of glial cell responses in the brain. In the present study we describe the expression of IL-10 and the IL-10 receptor (IL-10R1) in primary cocultures of rat microglial and astroglial cells. Using quantitative RT-PCR and ELISA, we show that IL-10 mRNA expression and subsequent IL-10 secretion is time-dependently induced by lipopolysaccharide (LPS). IL-10R1, however, is constitutively expressed in glial cell cocultures, as shown by RT-PCR and immunocytochemistry. Radioligand binding studies using 125I-IL-10 reveal that rat glial cells express a single binding site with an apparent affinity of approximately 600 pm for human IL-10. Observations in enriched cultures of either microglial or astroglial cells indicate that both cell types express IL-10 mRNA and are capable of secreting IL-10. Both cell types also express IL-10R1 mRNA and protein. However, in glial cell cocultures immunoreactive IL-10R1 protein is predominantly observed in astrocytes, suggesting that microglial expression of IL-10R1 in cocultures is suppressed by astrocytes. In addition, exogenous IL-10 is highly potent in down-regulating LPS-induced IL-1beta and IL-10 mRNA, and, at a higher dose, IL-10R1 mRNA in untreated and LPS-treated cultures, suggesting that IL-10 autoregulates its expression and inhibits that of IL-1beta at the transcriptional level. Together the findings support the concept that IL-10, produced by activated microglial and astroglial cells, modulates glia-mediated inflammatory responses through high-affinity IL-10 receptors via paracrine and autocrine interactions.