A series of 7,8-disubstituted guanosine derivatives was designed and prepared as potential B-cell-selective activators of the humoral immune response. These compounds were evaluated for their ability to act as B-cell mitogens and to augment the antibody response of B cells to sheep red blood cell (SRBC) challenge (adjuvanticity). In addition, they were tested for their ability to stimulate the natural killer (NK) cell response in murine in vitro cell assays. Certain of the compounds demonstrated in vivo activity when administered either intravenously, subcutaneously, or orally. Analogues with a medium-length alkyl chain (2-4 carbons, 5-7) on the 7-position of 7-alkyl-8-oxoguanosines were found to be particularly potent. Compounds bearing hydroxyalkyl, aminoalkyl, or substituted aminoalkyl substituents on this 7-position were weakly active. However, benzyl groups, including those substituted with heteroatoms (e.g., p-nitrobenzyl, 14), were active. Oxo, thioxo, and seleno groups on C-8 of the guanosine ring all imparted strong activity, whereas other larger substituents did not (e.g., N = CN). Stereochemical inversion of the 2'-hydroxyl on the ribose ring in this series, giving arabinose analogue 70, lessened activity. However, removal of the 2'-hydroxyl, either with (64) or without (73) removal of the 3'-hydroxyl, resulted in excellent activity and improved solubility; 64 also displayed good oral in vivo activity as well. A series of ketals involving the 2',3'-hydroxyls were prepared; certain of the nonpolar ketals (e.g., 48) were remarkably active, pointing to an ancillary hydrophobic binding region that can augment activity. 5'-Phosphate derivative 57 was fairly active, and acyclovir analogue 90 displayed good NK-selective activity: other N-9 sugar mimetics were also active (97-104), although this activity did not carry over into the human B-cell assay. A total of 80 compounds were prepared and evaluated for their immunostimulating activity. Within this group, compounds could be divided into those that were active in all three assays, those that displayed some measure of selectivity for the adjuvanticity assay, and those that preferentially activated NK responses. Because of its overall biological profile and ease of synthesis, 7-allyl-8-oxoguanosine (6; loxoribine, RWJ-21757) was chosen for further development. It is among the most potent compounds evaluated in the three biological assays.
There have been many reports of cases in which chronic increases in the numbers of natural killer (NK) cells have been reported. Whether this is reactive or neoplastic in nature has been debated. We report the first case of an aggressive NK cell leukemia in an adult with establishment of an NK cell line. A 70-year-old man had two spontaneous episodes of jejunal perforation and one month later developed a severe febrile illness with moderate splenomegaly. Hemoglobin was 13.1 g/L, and WBC count was 1.8 X 10(9)/L with 2% large granular lymphocytes (LGLs). Platelet count was 143 X 10(9)/L; prothrombin time (PT) and partial thromboplastin time (PTT) were normal. Bone marrow was infiltrated with 25% to 30% LGLs; serum lysozyme was normal. Serum LDH was initially 1,191 U/L and rose to 6,408 (normal 240 to 525 U/L). Ten days later, the WBC count increased to 99.9 X 10(9)/L with 70% LGL cells; the PT and PTT increased, and the platelet count dropped. No bacterial or viral cause of fever was identified. The cells from peripheral blood were LGLs that stained positively for acid phosphatase. All of the LGLs reacted with a monoclonal antibody reactive with NK cells (LEU-11b). Functionally, the patient's peripheral blood mononuclear cells (PBMs) demonstrated 100 times more lytic activity against K562 tumor cell lines than did normal PBMs. The patient's PBMs were propagated in vitro. The cultured cells showed the morphological, cytochemical, immunological, and functional characteristics of NK cells. In addition, partial trisomy involving chromosome 1 q with duplication in regions of q21 through q31 was observed in all metaphases analyzed. The extra chromosome 1q with duplication in regions q21 through q31 was translocated to the p- terminal of chromosome 5. One percent to 5% of normal PBMs comprise NK cells; in most cases, leukemias arise from normal phenotypic counterparts. This case demonstrated that aggressive NK cell leukemia may occur in adults. In addition, the chromosomal abnormalities suggest that this is not a reactive process but a malignancy.
Inflammation is characterized by the migration of polymorphonuclear leukocytes from the vasculature into the tissue causing profound injury. Adhesion and migration of neutrophils across the vascular bed are governed by a series of complex events including cytokine/chemokine production which in turn orchestrates the temporal expression of a cohort of adhesion molecules mediating the migration. Many of these adhesion molecules and their inducers are under the control of inflammatory response transcriptional factors such as NF kappa B and AP-1. Recently we showed tepoxalin, previously known as a dual cyclooxygenase/lipoxygenase (CO/LO) inhibitor, to be a potent inhibitor of NF kappa B-induced transcription in vitro. In this study, we demonstrated that when administered in vivo, tepoxalin but not naproxen (a nonsteroidal anti-inflammatory drug, NSAID) or zileuton (an LO inhibitor), effectively inhibits neutrophil migration into inflammatory sites in murine skin stimulated by either lipopolysaccharide (LPS) or tumor necrosis factor-alpha. Immunohistochemical analysis indicates that 10-50 mg/kg of tepoxalin inhibits neutrophil migration. It also effectively blocks the upregulation of Mac-1 (CD11b/CD18) on neutrophils. Quantitative polymerase chain reaction Mac-1 analysis shows that LPS-induced transcription of E-selectin mRNA was dramatically suppressed by both 25 and 50 mg/kg of tepoxalin, whereas the level of ICAM-1 was only affected by 50 mg/kg of tepoxalin. Since it has been documented that the expression of E-selectin and Mac-1 is regulated either directly or indirectly by the transcription factor NF kappa B, our studies provide in vivo evidence that tepoxalin is a potent inhibitor of NF kappa B-mediated events in animal models and this novel molecular mechanism clearly defines it as a new class of anti-inflammatory compounds.
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