Quantitative Western blot assay for measurement of the murine acute phase reactant, serum amyloid P component

Bacterial lipopolysaccharide potentiates type II collagen-induced arthritis in mice

Collagen-induced arthritis (CIA) is an immunologically relevant animal model of human rheumatoid arthritis. Studies comparing the disease incidence in genetically susceptible male and female DBA/1LacJ mice demonstrated that under low density/low stress housing conditions, female mice had earlier onset (day 35) and higher disease incidence (25%) than the male mice (17% at day 49) when immunized with bovine type II collagen. A single subcutaneous or intraperitoneal injection of bacterial lipopolysaccharide (LPS) 17–24 days after collagen immunization greatly potentiated this standard CIA model in a dose related manner. 20–40 μg of LPS accelerated the onset of disease from day 35 to day 21 and exacerbated the clinical severity score from 0.27 to 2.00 at day 42. A similar administration of 6 μg of recombinant interleukin-β produced a comparable potentiated CIA model. The acute phase protein, serum amyloid P (SAP), was elevated in the serum at day 26 to 440 μg ml⁻¹ for the LPS potentiated CIA mice compared to 65 μg ml⁻¹ in the non-potentiated immunized CIA mice. There was a significant correlation (r = 0.78) between SAP levels and disease expression in the LPS treated CIA mice. The rapidity and uniformity of disease expression in this LPS potentiated CIA model will allow more and different drugs to be evaluated with a smaller number of animals.

Effects of lipopolysaccharide-stimulated inflammation and pyrazole-mediated hepatocellular injury on mouse hepatic Cyp2a5 expression

Murine hepatic cytochrome P450 2a5 (Cyp2a5) is induced during hepatotoxicity and hepatitis, however, the specific regulatory mechanisms have not been determined. We compared the influence of acute inflammation elicited in vivo by bacterial endotoxin lipopolysaccharide (LPS) and liver injury caused by the hepatotoxin pyrazole on hepatic Cyp2a5 expression in mice. Pyrazole treatment resulted in statistically significant increases in levels of Cyp2a5 mRNA, protein and catalytic activity by 540, 273 and 711%, respectively (P<0.05). In LPS-treated livers Cyp2a5 expression was significantly reduced compared to controls at the mRNA (46%) protein (35%), and activity (23%) levels (P<0.05). Treatment of mice with recombinant murine interleukin-1 beta and interleukin-6 had no significant effect on Cyp2a5 mRNA and protein levels. Liver injury, as assessed by serum alanine aminotransferase, was greater with pyrazole than with LPS treatment (609 vs 354% of control levels respectively). ER stress, determined by hepatic glucose regulated protein 78 (grp78) levels, was greater with pyrazole (185% of controls) than with LPS (128% of controls). In pyrazole-treated liver, overexpression of immunoreactive grp78 protein revealed that ER stress was localized to pericentral hepatocytes in which Cyp2a5 was induced. Evidence of glycogen loss and membrane damage in these cells was suggestive of oxidative damage. Moreover, vitamin E attenuated Cyp2a5 induction by pyrazole in vivo. These results suggest that induction of Cyp2a5 that has been observed in mouse models of hepatitis and hepatoxicity may be related to oxidative injury to the endoplasmic reticulum of pericentral hepatocytes rather than exposure to pro-inflammatory cytokines.

Activation of the IL-1 gene in UV-irradiated mouse skin: association with inflammatory sequelae and pharmacologic intervention

The relationship between ultraviolet irradiation, interleukin-1 production, and inflammatory sequelae and the pharmacologic inhibition of these events was investigated in Balb/c mice exposed to ultraviolet irradiation from a bank of six Westinghouse FS40 sunlamps. The resulting edema (66% increase), inflammatory cell infiltration, and rise in the acute-phase reactant (fourfold) serum amyloid P component was preceded by the activation of the interleukin-1 beta gene and enhanced product formation. Administration of dexamethasone, which is known to inhibit interleukin-1 production, inhibited the inflammatory response to ultraviolet irradiation. Thus, production of interleukin-1 may be one of the initial events leading to the consequences of ultraviolet irradiation exposure.

Identification of the residues in human CD4 critical for the binding of HIV

The CD4 molecule is a T cell surface glycoprotein that interacts with high affinity with the envelope glycoprotein of the human immunodeficiency virus, HIV, thus serving as a cellular receptor for this virus. To define the sites on CD4 essential for binding to gp120, we produced several truncated, soluble derivatives of CD4 and a series of 26 substitution mutants. Quantitative binding analyses with the truncated proteins demonstrate that the determinants for high affinity binding lie solely with the first 106 amino acids of CD4 (the V1 domain), a region having significant sequence homology to immunoglobulin variable regions. Analysis of the substitution mutants further defines a discrete binding site within this domain that overlaps a region structurally homologous to the second complementarity-determining region of antibody variable domains. Finally, we demonstrate that the inhibition of virus infection and virus-mediated cell fusion by soluble CD4 proteins depends on their association with gp120 at this binding site.

Effect of inhibitors of eicosanoid metabolism in murine collagen-induced arthritis

The dual inhibitors of arachidonic acid metabolism, Smith Kline & French (SK&F) 86002, SK&F 104351, and phenidone; the corticosteroid, dexamethasone; and the selective cyclooxygenase inhibitors, ibuprofen, indomethacin, naproxen, and piroxicam were evaluated for their antiarthritic potency in the murine, collagen-induced arthritis model. The ability of these compounds to alter the severity of arthritic lesions and to reduce serum levels of the acute-phase reactant, serum amyloid P component (SAP) were monitored. Serum concentrations of SAP were found to correlate strongly (r = 0.985) with disease severity at day 35 postimmunization. Treatment with SK&F 86002, SK&F 104351, phenidone, or dexamethasone significantly reduced disease severity, as judged by clinical score (55%, 72%, 41%, and 45% inhibition, respectively) and SAP levels (62%, 94%, 52%, and 94% inhibition, respectively) in arthritic mice. This profile of activity was not shared by the selective cyclooxygenase inhibitors, which did not uniformly inhibit disease activity by both parameters. The results suggest that dual inhibitors of 5-lipoxygenase and cyclooxygenase may prove more effective than selective cyclooxygenase inhibitors as anti-arthritic agents.

Quantification of immunoglobulin on electrophoretic immunoblot strips as a tool for human immunodeficiency virus serodiagnosis

Electrophoretic immunoblotting (EIB [Western blotting]), the main method for verification of human immunodeficiency virus (HIV) seropositivity, needs thorough characterization and standardization. We explored the possibilities of quantifying immunoglobulin G (IgG) bound to EIB strips both by densitometry of the peroxidase-stained bands and by measurement of radioactivity with labeled anti-HIV IgG. The radioactivity method is inherently more exact but was more cumbersome. However, despite saturation phenomena at high IgG densities, the densitometric method was more convenient and yielded reproducible estimates of the amount of bound IgG. We found it useful primarily for documentation of changes in the relative abundance of antibodies to different HIV proteins from individual patients over time. To explore the potential usefulness of the method, we studied a small set of HIV-seropositive persons. The average p24/gp41 color yield ratios and standard deviations in 3 persons with recent seroconversion, 15 healthy subjects, and 6 diseased HIV-seropositive persons were 6.6 +/- 0.9, 2.3 +/- 1.9, and 1.3 +/- 0.5, respectively. These data are in accord with previous qualitative or semiquantitative observations but are too limited for any conclusions regarding the use of quantitative EIB for prognostic use with individual patients. Quantitative EIB is a valuable tool for comparative methodological studies and for research on the protective role of anti-HIV antibodies in acquired immunodeficiency syndrome pathogenesis. Its possible use in prognostication for individual patients must be evaluated in long-term studies.