Hypoglycemia in mice injected with interferon inducers is not mediated by interferon

Viral double-stranded RNA, cytokines, and the flu

The symptoms of the flu, such as fever, drowsiness, and malaise, are the sole means by which this common clinical syndrome is defined. The syndrome is usually the first clinical manifestation of both acute bacterial and viral infections. In the case of acute bacterial infections, several proinflammatory cytokines induced by bacterial products have been implicated as the causative agents of the flu syndrome. Viruses induce similar cytokines to bacteria, plus substantial amounts of interferon-alpha (IFN-alpha), although the direct association of these cytokines with the viral flu syndrome is less clear. Furthermore, the viral inducer(s) of cytokines has not been defined. The best candidate cytokine inducer associated with a majority of viral infections is virus-associated double-stranded RNA (dsRNA). This review examines the essential physical properties of toxic dsRNA, the cytokines induced by it, its viral and cellular sources, evidence for its presence in infected cells, its quantities in normal and infected cells, its cytotoxic mechanisms, and its cell-penetration properties. Toxic effects of viruses and dsRNA are compared. Energetics and extraction artifact issues are also discussed. Whereas most research on dsRNA toxicity has employed synthetic dsRNA, studies with virus-associated dsRNA are featured when available. Finally, a model for how viral dsRNA might initiate systemic disease is presented.

Mechanism of virus-induced stimulation of the hypothalamus-pituitary-adrenal axis

Increased blood levels of glucocorticoids are observed during certain viral infections. In this paper, we report data obtained from a model in rodents showing that the pituitary-adrenal axis is stimulated following inoculation of Newcastle Disease Virus (NDV). No evidence for an ectopic, lymphoid source of ACTH-like immunoreactive material capable of inducing this effect was obtained. Administration of virus-free supernatants from cocultures of human peripheral blood leukocytes with NDV also stimulated ACTH and glucocorticoid output in normal mice. This observation showed the immunological cell origin of the mediator of the hormonal effect. Pretreatment of the supernatant with anti-IL-1 sera neutralized its capacity to induce an increase in glucocorticoid and ACTH levels in blood. Furthermore, injection of IL-1 in nanogram amounts also increased ACTH and glucocorticoid blood levels. Thus, we conclude that IL-1 is the most likely mediator of the stimulation of the pituitary-adrenal axis during viral infection. The reported data are also discussed in the general context of the postulated glucocorticoid-associated immunoregulatory circuit.

Interleukin 1-like factors can accumulate 5-hydroxytryptamine in the liver of mice and can induce hypoglycaemia

After the injection into mice of culture medium of P388D1 cells, a murine macrophage cell line, 5-hydroxytryptamine accumulated in the liver and blood glucose declined. The factors capable of inducing these responses were purified by gel filtration and chromatofocusing. With these procedures, the activity to induce the increase in 5-hydroxytryptamine in the liver accompanied the activity to induce hypoglycaemia. Moreover, through the purification, the factors were found in the fraction of interleukin 1, a lymphocyte-activating factor. These results suggest that the factors capable of inducing the increase in 5-hydroxytryptamine and hypoglycaemia are likely to be interleukin 1 molecules or molecules closely related to interleukin 1. The present and previous findings together with those in the literature support the idea that the increase in 5-hydroxytryptamine in the liver might be a cause of hypoglycaemia. These findings may provide new and important information about the roles of macrophages in inflammation or in immune responses.

Induction of hypoglycaemia and accumulation of 5-hydroxytryptamine in the liver after the injection of mitogenic substances into mice

Various mitogenic substances (concanavalin A, pokeweed mitogen, polyI : polyC and a phorbol diester), as well as lipopolysaccharides (LPS or endotoxins), produced hypoglycaemia after being injected into mice. However, non-mitogenic immuno-stimulants (zymosan, carrageenan, an adjuvant peptide and interferon) did not induce hypoglycaemia. All of the mitogenic substances also induced an increase in 5-hydroxytryptamine (5-HT) in liver, but the non-mitogenic substances did not have this effect. The time course of the development of hypoglycaemia was similar to that of the increase in liver 5-HT. The dose-dependence of the hypoglycaemia induced by LPS was similar to that of the increase in liver 5-HT. In C3H/HeJ mice, the macrophages and/or lymphocytes of the mice are known to be less responsive to LPS, and both the LPS-induced hypoglycaemia and increase in 5-HT were less in these mice than in control mice (C3H/He and ddI mice). These results suggest that macrophages and/or lymphocytes may participate in the induction of hypoglycaemia and the increase in 5-HT induced by mitogenic substances and LPS. A possible correlation between hypoglycaemia and the increase in hepatic 5-HT is discussed, although the relationship is not substantiated.