Erythropoietin (Epo), the hormone that stimulates red blood cell production, is synthesized in the kidney and liver in response to hypoxia. The human hepatoma cell line Hep3B regulates its production of Epo in a physiologic manner. Either hypoxia or cobalt chloride markedly increases expression of Epo mRNA as well as production of biologically active and immunologically distinct Epo protein. New protein synthesis is required before the induction of increased levels of hypoxia- or cobalt-induced Epo mRNA. Hypoxia, cobalt chloride, and nickel chloride appear to stimulate Epo production through a common pathway. The inhibition of Epo production at low partial pressures of oxygen by carbon monoxide provides evidence that a heme protein is integrally involved in the oxygen-sensing mechanism. This hypothesis is further supported by the finding that when heme synthesis is blocked, hypoxia-, cobalt-, and nickel-induced Epo production are all markedly inhibited. A model is proposed in which a ligand-dependent conformational change in a heme protein accounts for the mechanism by which hypoxia as well as cobalt and nickel stimulate the production of Epo.
No reports of the incidence rates for primary systemic amyloidosis (AL) have come to our attention. Records of all residents of Olmstead County, Minnesota, with a diagnosis of amyloidosis were obtained from the Mayo Clinic and its affiliated hospitals, as well as other medical groups that might have seen local patients for the period January 1, 1950 to December 31, 1989. Twenty-one patients fulfilled the criteria for the diagnosis of AL. The median age was 73.5 years, and 62% were men. In all but one patient the diagnosis was made ante mortem. The clinical data of the 21 patients were similar to those referral patients with AL seen at Mayo Clinic. Immunohistochemical stains were positive for monoclonal light chains in the amyloid deposits in 15 of the 21 cases. In six cases, tissue was not available for immunohistochemical studies. Three of the six patients without immunohistochemical stains had a free monoclonal lambda light chain in the urine, and the other three had a monoclonal serum protein. Immunoelectrophoresis/immunofixation detected a monoclonal (M)-protein in the serum of 16 of 17 patients tested. A monoclonal light chain was found in the urine of 10 of 15 patients. The overall sex- and age- adjusted rate per million person-years was 6.1 from 1950 to 1969 and 10.5 from 1970 to 1989. The similarity of these rates suggests no significant increase over time.
The effects of the inflammatory cytokines interleukin-1 alpha (IL-1 alpha), IL-1 beta, IL-6, transforming growth factor-beta (TGF-beta), and tumor necrosis factor-alpha (TNF-alpha) on erythropoietin (Epo) production in Hep3B cells were examined. The addition of IL-1 alpha, IL- 1 beta, or TNF-alpha resulted in a dose-dependent inhibition of hypoxia- induced Epo production by as much as 89%. IL-1 beta was the most effective cytokine tested, demonstrating half-maximal inhibition at 0.4 U/mL compared with 1.0 and 10.0 U/mL for IL-1 alpha and TNF-alpha, respectively. TGF-beta also inhibited hypoxia-induced Epo production, but only by as much as 56%. In contrast to IL-1 alpha, IL-1 beta, TNF- alpha, and TGF-beta, the addition of IL-6 to hypoxic Hep3B cells resulted in a dose-dependent stimulation of hypoxia-induced Epo production by as much as 81%. However, IL-6 did not stimulate Epo synthesis in the absence of hypoxia, and was thus synergistic with hypoxia in inducing Epo production. Combinations of IL-1 alpha, TNF- alpha, and IL-6 were found to be additive in their effects on hypoxia- induced Epo production. By Northern blot analysis, Epo messenger RNA levels in Hep3B cells grown in 1% O2 were decreased when concurrently exposed to either IL-1 alpha or TNF-alpha. The effects that IL-1 alpha, IL-1 beta, TGF-beta, TNF-alpha, and IL-6 have on hypoxia-induced Epo production may provide new insights into the signal transduction pathway by which hypoxia leads to changes in gene expression. In addition, the effects of these inflammatory cytokines on hypoxia- induced Epo production in vitro suggest that in various inflammatory disorders these cytokines may affect Epo production in vivo and may play a significant role in the pathogenesis of the anemia of chronic disease.
Patients who undergo bone marrow transplantation are generally immunosuppressed with a dose of cyclophosphamide (CYA) which is usually calculated based on the patient's weight. At these high doses of CYA, serious cardiotoxicity may occur, but definitive risk factors for the development of such cardiotoxicity have not been described. Since chemotherapeutic agent toxicity generally correlates with dose per body surface area, we retrospectively calculated the dose of CYA in patients transplanted at our institution to determine whether the incidence of CYA cardiotoxicity correlated with the dose per body surface area. Eighty patients who were to receive CYA 50 mg/kg/d for four days as preparation for marrow grafting underwent a total of 84 transplants for aplastic anemia, Wiskott-Aldrich syndrome, or severe combined immunodeficiency syndrome. Fourteen of 84 (17%) patients had symptoms and signs consistent with CYA cardiotoxicity within ten days of receiving 1 to 4 doses of CYA. Six of the 14 patients died with congestive heart failure. The dose of CYA per body surface area was calculated for all patients and the patients were divided into two groups based on daily CYA dose: Group 1, CYA less than or equal to 1.55 g/m2/d; Group 2, CYA greater than 1.55 g/m2/d. Cardiotoxicity that was thought to be related to CYA occurred in 1/32 (3%) of patients in Group 1 and in 13/52 (25%) patients in Group 2 (P less than 0.025). Congestive heart failure caused or contributed to death in 0/32 patients in Group 1 v 6/52 (12%) of patients in Group 2 (P less than 0.25). There was no difference in the rate of engraftment of evaluable patients in the two groups (P greater than 0.5). We conclude that the CYA cardiotoxicity correlates with CYA dosage as calculated by body surface area, and that patients with aplastic anemia and immunodeficiencies can be effectively prepared for bone marrow grafting at a CYA dose of 1.55 g/m2/d for four days with a lower incidence of cardiotoxicity than patients whose CYA dosage is calculated based on weight. This study reaffirms the principle that drug toxicity correlates with dose per body surface area.
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