L-Asparaginase is important in the induction regimen for treating acute lymphoblastic leukemia. Cytotoxic complications are clinically significant problems lacking mechanistic insight. To reveal tissue-specific molecular responses to this drug, mice were administered asparaginase from either Escherichia coli (clinically used) or Wolinella succinogenes (novel, glutaminasefree form). Both enzymes abolished serum asparagine, but only the E. coli form reduced circulating glutamine. E. coli asparaginase reduced protein synthesis in liver and spleen but not pancreas via increased phosphorylation of the translation factor eIF2. In contrast, treatment with Wolinella caused no untoward changes in protein synthesis in any tissue examined. Treating mice deleted for the eIF2 kinase, GCN2, with the E. coli enzyme showed eIF2 phosphorylation to be GCN2-dependent, but only initially. Furthermore, although eIF2 phosphorylation was not increased in the pancreas or by Wolinella asparaginase, expression of the amino acid stress response genes, asparagine synthetase and CHOP/GADD153, increased as a result of both enzymes, even in tissues demonstrating no change in eIF2 phosphorylation. Finally, signaling downstream of the mammalian target of rapamycin kinase was repressed in liver and pancreas by E. coli but not Wolinella asparaginase. These data demonstrate that the nutrient stress response to asparaginase is tissuespecific and exacerbated by glutamine depletion. Importantly, increased expression of asparagine synthetase and CHOP does not require eIF2 phosphorylation, signifying alternate or auxiliary means of inducing gene expression under conditions of amino acid depletion in the whole animal.

Cytokine mRNA expression and stimulus-induced cytokines were examined in peripheral blood mononuclear cells in 62 human immunodeficiency virus (HIV)-infected children and uninfected controls. Compared with that in controls, constitutive mRNA expression in patients was increased for tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, and interleukin (IL)-10 and decreased for IL-12; it was undetectable for IL-2 and IL-4 in both patients and controls. Stimulus-induced secretion of TNF-alpha, IFN-gamma, IL-12, and IL-4 was less than that in controls; IL-10 secretion was similar. There was no increase in stimulus-induced or constitutive IL-4 or IL-10 in children with severe immunologic deficit compared with controls. A higher stimulus-induced IL-10 secretion and a lower constitutive TNF-alpha mRNA were associated with a slower rate of disease progression, and TNF-alpha mRNA expression correlated with lower plasma HIV RNA. Thus, constitutive cytokine mRNA expression differs from stimulus-induced cytokine responses. The dominant defect in HIV-infected children appears to be one of reduced type 1 cytokines, predominantly IL-2.