The role of the glucocorticoid receptor {GR1 in glucocorticoid physiology and during development was investigated by generation of GR-deficient mice by gene targeting. GR -/-mice die within a few hours after birth because of respiratory failure. The lungs at birth are severely atelectatic, and development is impaired from day 15.5 p.c. Newborn livers have a reduced capacity to activate genes for key gluconeogenic enzymes. Feedback regulation via the hypothalamic-pituitary-adrenal axis is severely impaired resulting in elevated levels of plasma adrenocorticotrophic hormone (15-fold) and plasma corticosterone (2.5-fold). Accordingly, adrenal glands are enlarged because of hypertrophy of the cortex, resulting in increased expression of key cortical steroid biosynthetic enzymes, such as side-chain cleavage enzyme, steroid 11B-hydroxylase, and aldosterone synthase. Adrenal glands lack a central medulla and synthesize no adrenaline. They contain no adrenergic chromaffin cells and only scattered noradrenergic chromaffin cells even when analyzed from the earliest stages of medulla development. These results suggest that the adrenal medulla may be formed from two different cell populations: adrenergic-specific cells that require glucocorticoids for proliferation and/or survival, and a smaller noradrenergic population that differentiates normally in the absence of glucocorticoid signaling.

IL-18 is synthesized as a precursor molecule without a signal peptide but requires the IL-1beta converting enzyme (ICE, caspase-1) for cleavage into a mature peptide. Human precursor IL-18 was expressed, purified, and cleaved by ICE into a 18-kD mature form. Mature IL-18 induced IL-8, macrophage inflammatory protein-1alpha, and monocyte chemotactic protein-1 in human peripheral blood mononuclear cells in the absence of any co-stimuli. Blocking IL-1 with IL-1 receptor antagonist resulted in a 50% reduction in IL-8. Neutralization of TNF with TNF binding protein resulted in a 66% reduction in IL-1beta, an 80% reduction of IL-8, and an 88% reduction in mean TNFalpha mRNA. In purified CD14+ cells but not CD3+/CD4+, IL-18 induced gene expression and synthesis of IL-8 and IL-1beta. TNFalpha production was induced in the non-CD14+ population and there was no induction of TNFbeta by IL-18. In purified natural killer cells, IL-18 induced IL-8 that was also inhibited by TNF binding protein. IL-18 did not induce antiinflammatory cytokines, IL-1Ra, or IL-10, although IL-18 induction of TNFalpha was inhibited by IL-10. In the presence of IFNgamma, IL-18-induced TNFalpha was enhanced and there was an increase in the mature form of IL-1beta. We conclude that IL-18 possesses proinflammatory properties by direct stimulation of gene expression and synthesis of TNFalpha from CD3+/CD4+ and natural killer cells with subsequent production of IL-1beta and IL-8 from the CD14+ population.

SummarySystemic and localized inflammation elicit a number of host responses which include fever, cachexia, hypoglycemia, and major changes in the concentration of liver plasma proteins. Interlenkin 6 (IL-6) is considered an important mediator of the inflammatory response, together with IL-1 and tumor necrosis factor c~ (TNF-c 0. The purpose of this study was to unequivocally determine the role of IL-6 in these phenomena making use of IL-6-deficient mice that we have recently generated by gene targeting. We report here that in the absence of IL-6, mice are unable to mount a normal inflammatory response to localized tissue damage generated by turpentine injection. The induction of acute phase proteins is dramatically reduced, mice do not lose body weight and only suffer from mild anorexia and hypoglycemia. In contrast, when systemic inflammation is elicited through the injection of bacterial lipopolysaccharide (LPS), these parameters are altered to the same extent both in wild-type and IL-6-deficient mice, demonstrating that under these conditions IL-6 function is dispensable. Moreover, we show that LPS-treated IL-6-deficient mice produce three times more TNF-c~ than wild-type controls, suggesting that increased TNF-c~ production might be one of the compensatory mechanisms through which a normal response to LPS is achieved in the absence of IL-6. We also show that corticosterone is normally induced in IL-6-deficient mice, demonstrating that IL-6 is not required for the activation of the hypothahmicpituitary-adrenal axis. Our results reinforce the idea that different patterns of cytokines are involved in systemic and localized tissue damage, and identify IL-6 as an essential mediator of the inflammatory response to localized inflammation.

IntroductionIn the kidney, activation of caspases has been described during hypoxic proximal tubular necrotic injury in vitro and pan-caspase inhibition protects against this injury (1, 2). A recent study demonstrates that a pan-caspase inhibitor protects against ischemic ARF in mice by inhibition of distal tubule apoptosis and subsequent inflammation (3). In this study, however, the effect of caspase inhibition on the development of ischemic acute tubular necrosis (ATN), a well-established mechanism of tubular injury, was not studied. Also, in these studies, the use of pan-caspase inhibitors makes it difficult to implicate a specific caspase in hypoxic/ischemic injury. Thus, the mechanism of caspase-mediated ischemic ARF and the specific caspase involved in this renal ischemia-reperfusion injury is not clear.The caspases are a family of intracellular cysteine proteases. Caspases participate in two distinct signaling pathways: (a) activation of proinflammatory cytokines and (b) promotion of apoptotic cell death (4). Caspase-1 (previously known as IL-1β-converting enzyme or ICE) plays a major role in the cleavage of the IL-1β precursor and the IL-18 precursor. Caspase-1 is remarkably specific for these precursors of IL-1β and IL-18 (IFN-γ-inducing factor) by making a single initial cut in each procytokine, which results in an active mature cytokine secreted into the extracellular space (5, 6). Although thymocytes from caspase-1 -/-mice were found to be resistant to apoptosis induced by Fas Ab (7), subsequent studies did not demonstrate a role of caspase-1 in apoptosis (8).To establish a pathogenic role of caspase-1 in cell injury, caspase-1 -/-mice have been used. These caspase-1 -/-mice have a defect in production of mature IL-1β and IL-18 and are protected against lethal endotoxemia (7,8). The fact that IL-1β -/-mice are not protected against endotoxemia (9) suggests a potential role of IL-18 in the lethal outcome during sepsis. Moreover, in ischemic ARF, IL-1 receptor-knockout mice or mice treated with IL-1-receptor antagonist (IL-1Ra) are not protected against ischemic ARF (10). Taken together, therefore, these previous studies suggest that IL-18 may be a potential mediator of ischemic ARF. Thus, any protective effect against renal ischemia-reperfusion injury in caspase -/-mice may be due to a failure of this caspase to activate IL-18.In the present study, we used caspase-1 -/-mice to test the hypothesis that caspase-1 is a mediator of ischemic ARF in mice. The fact that expression of the proinflammatory cytokines IL-1β and IL-18 is altered in caspase-1 -/-mice makes these mice a very suitable model for further studying the mechanism of ischemic ARF. Thus, the aims of the present study were to determine whether caspase-1 -/-mice are protected against ischemic ARF and to explore the mechanisms of this protection, particularly the role of IL-18. We sought to determine whether mice deficient in the proinflammatory caspase-1, which cleaves precursors of IL-1β and IL-18, were protected against ischemic acute renal...

These findings indicate that although they receive the same medical therapy as patients who do not experience an in-hospital event, patients with unstable angina and with complicated in-hospital courses have higher cytokine levels on admission. A fall in IL-1Ra and IL-6 48 hours after admission was associated with an uneventful course and their increase with a complicated hospital course. These findings may suggest novel therapeutic approaches to patients with unstable angina.