Lysosome stabilization by adjuvant arthritis serum

Regulation of macrophage activation and inflammation by spermine: a new chapter in an old story

Spermine, a naturally occurring polyamine, is a ubiquitous structural component of all eukaryotic cells. Regenerating tissues produce higher levels of spermine, and injured or dying cells release spermine into the extracellular milieu, so that tissue levels increase significantly at inflammatory sites of infection or injury. Recent research has focused on delineating the significance of spermine accumulation in the inflammatory process. The discovery that spermine is a negative regulator of macrophage activation provided a mechanism by which spermine influences the biology of inflammation. Mechanistic studies indicate that spermine is incorporated into macrophages and restrains the innate immune response. This anti-inflammatory process is facilitated by the negative acute-phase protein, fetuin.

Spermine inhibits proinflammatory cytokine synthesis in human mononuclear cells: a counterregulatory mechanism that restrains the immune response

The local production of proinflammatory cytokines mediates the host response to inflammation, infection, and injury, whereas an overexpression of these mediators can injure or kill the host. Recently, we identified a class of multivalent guanylhydrazone compounds that are effective inhibitors of proinflammatory cytokine synthesis in monocytes/macrophages. The structure of one such cationic molecule suggested a molecular mimicry with spermine, a ubiquitous endogenous biogenic amine that increases significantly at sites of inflammation and infection. Here, we addressed the hypothesis that spermine might counterregulate the innate immune response by downregulating the synthesis of potentially injurious cytokines. When spermine was added to cultures of human peripheral blood mononuclear cells stimulated with lipopolysaccharide (LPS), it effectively inhibited the synthesis of the proinflammatory cytokines tumor necrosis factor (TNF), interleukin-1 (IL-1), IL-6, MIP-1alpha, and MIP-1beta. The inhibition of cytokine synthesis was specific and reversible, with significant inhibition of TNF synthesis occurring even when spermine was added after LPS. The mechanism of spermine-mediated cytokine suppression was posttranscriptional and independent of polyamine oxidase activity. Local administration of spermine in vivo protected mice against the development of acute footpad inflammation induced by carrageenan. These results identify a distinct molecular counterregulatory role for spermine in downregulating the monocyte proinflammatory cytokine response.

Polyamine oxidase activity in rheumatoid arthritis synovial fluid

Oxidation of polyamides by polyamine oxidases (PAO) leads to the generation of highly reactive aminoaldehydes which have been shown to have a variety of effects, including killing of pathogenic microorganisms and regulation of leucocyte functions. Data presented here show that PAO are present in synovial fluid from patients with rheumatoid arthritis. This finding may have important implications in the various properties attributed to synovial fluid which includes anti-inflammatory activity.

Inhibition of the respiratory burst of human neutrophils by the polyamine oxidase-polyamine system

The addition of the polyamines, spermine and spermidine, to human neutrophils caused a depression of the hexose-monophosphate (HMP) shunt activity of neutrophils stimulated with latex particles but not of unstimulated cells. The effect was dependent on the presence of bovine serum and was not observed when normal human serum was substituted for bovine serum. The polyamine oxidase (PAO) in bovine serum was probably responsible for generating the activity since normal human serum lacks PAO. A role for PAO was further supported by the finding that partially purified bovine PAO in the presence of polyamines similarly mediated inhibition of HMP shunt activity in stimulated neutrophils. Catalase failed to prevent the inhibitory effects of the PAO-polyamine system suggesting that H2O2 is not the responsible product. In addition, our results show that human pregnancy serum known to contain PAO activity in the presence of polyamines mediated a similar inhibition of the respiratory burst.

Anti-inflammatory factors in sponge-induced exudate in the rat

Sterile polyester sponge-induced exudates in the rat have been investigated for high molecular weight substances with anti-inflammatory activity against carrageenan-induced oedema in the rat. The only substances found with this activity were dialysable molecules. Crude but sterile protein fractions isolated from exudate stabilized guinea-pig macrophages at low concentrations. The proteins present in exudates appeared to be identical to normal rat plasma proteins. It is concluded that anti-inflammatory activity associated with high molecular substances in exudate may have been due to bacterial contamination.

Putrescine--a potent endogenous anti-inflammatory substance in inflammatory exudates

Sponge-induced exudate from the rat and saline extracts of normal rat liver and rat liver damaged in situ by dimethylnitrosamine have been assayed for putrescine, spermidine and spermine levels. The three physiological oligoamines have been examined for anti-inflammatory activity by the carrageenan-induced oedema rat model and spermidine and putrescine were found to be anti-inflammatory with putrescine being about ten times as active as spermidine. Putrescine was also anti-inflammatory in the adjuvant arthritic rat model. Thioacetamide and theophylline were also anti-inflammatory and theophylline doubled the level of putrescine in rat liver. It was concluded that putrescine was a potent anti-inflammatory factor in the inflammatory exudates and extracts examined.

Inflammation, counter irritation and rat serum acute phase alpha 2-macroglobulin levels

Following the injection of turpentine and carrageenan into rats, laboratory models for counter irritation were assessed by measuring changes in paw thicknesses and serum acute phase alpha 2-macroglobulin concentrations. Both indices of inflammation were also examined in groups of rats dosed with 6-mercaptopurine, the best inhibitor found so far of elevated levels of alpha 2-macroglobulin in rat serum. Results showed that there is no relationship between the degree of irritant-induced inhibition of inflammation and the serum concentration of the acute phase protein. Hence, at least in the models for counter irritation used in this study, alpha 2-macroglobulin cannot be viewed as an endogenous anti-inflammatory protein.

Involvement of prostaglandins from rheumatoid synovium in inhibition of articular cartilage metabolism

Short term incubations of articular cartilage in media from cultures of rheumatoid synovial tissue result in marked inhibition of 3H-glycine and Na235SO4 incorporation into trichloroacetic acid (TCA) insoluble macromolecules by the cartilage segments with little effect on degradation of prelabeled cartilage matrix. This inhibition is time dependent and not observed in cartilage segments incubated in media derived from rheumatoid synovia cultured in the presence of indomethacin (a specific inhibitor of prostaglandin synthesis). In addition, no indomethacin-sensitive cartilage inhibitory activity was detectable in media from cultures of normal synovia. The ether solubility of the majority of the inhibitory activity and the indomethacin sensitivity suggest that the inhibitor(s) are prostaglandins.

Protease and antiprotease levels in blood of arthritic rats

Protease, antiprotease, and acid phosphatase blood levels of adjuvant arthritic rats were determined. The protease levels appear to vary inversely with the antiprotease levels. Changes in the protease levels correspond closely to changes in the acid phosphatase levels. Thus it is likely that the lysosomes contribute to the proteases present in the blood. Administered cortisol appears to raise blood antiprotease levels in both normal and arthritic rats and this may reflect an anti-inflammatory action by this drug.

Effects of steroid hormones on human polymorphonuclear leukocyte lysosomes

Lysosomal membrane stabilization has been proposed as a mechanism for the anti-inflammatory action of corticosteroid hormones. This hypothesis was based on studies with liver organelles. We studied the action of steroids on intact lysosomes isolated from human peripheral blood polymorphonuclear (PMN) leukocytes. Both androstenedione and progesterone, 10(-3)-10(-5) M, caused leakage of acid hydrolase markers from these organelles, thus resembling their effects on liver lysosomes. But none of the anti-inflammatory steroids tested protected organelle membranes from either detergent lysis (Triton X-100) or heat incubation (37 degrees C, 90 min). Hydrocortisone (HC), HC sodium succinate, HC acetate, HC hemisuccinate, prednisone, and dexamethasone were without detectable stabilizing activity at concentrations of 10(-3)-5 x 10(-8) M. Release of the lysosomal marker, beta-glucuronidase, was not retarded by any of the compounds studied. In addition, PMN leukocyte lysosomes isolated from human volunteers receiving prednisolone were not more stable than control organelles, nor did serum from steroid-treated humans protect intact lysosomes from detergent lysis. Variations in cholesterol and phospholipid contents of liver and PMN leukocyte lysosome membranes could possibly account for the different reactivity to corticosteroids observed. We believe that the anti-inflammatory activity of adrenal corticosteroids can best be explained by their inhibitory effects on cellular metabolism rather than by their direct interaction with lysosomal membranes.