E. Myles Glenn

The systemic response to inflammation

Abstract Various acute phase reactants (APR) have been studied in rats with different types of inflammation. These APR (serum albumin, serum globulins, plasma fibrinogens, serum alpha-2-glycoprotein [GP], total serum glycoproteins, serum mucoproteins) and neutrophils and lymphocytes reflect the onset, intensity, and duration of many types of experimental inflammation. The APR and cellular changes, like the inflammatory processes eliciting them, are stereotyped. Chemically induced, chronic immunologic, and delayed hypersensitivity-type acute inflammatory reactions cannot be distinguished by the APR. The most sensitive and quantitatively reliable index for the assessment of the “anti-inflammatory” action of the various steroidal and nonsteroidal drugs is the behaviour of the serum alpha-2-glycoproteins. This is also the most sensitive index of the “anti-inflammatory” action of adrenocortical steroids (or their absence, as shown in adrenalectomized rats). The various serum protein changes in rats with inflammation occur in response to greater sequestration rates at the sites of inflammation. Acute and chronic inflammation can be induced with a variety of substances affecting cell membranes (Filipin, digitonin, saponin, nystatin, d -α-tocopherol, vitamin A, and etruscomycin, to name but a few). These inflammatory reactions are inhibited in vivo by both steroidal and nonsteroidal “anti-inflammatory” drugs. We have visualized the process of inflammation as a wave of leaky membranes. The protective effects of nonsteroidal “anti-inflammatory” drugs on heat-induced and hypotonic erthrocyte lysis in vitro partially confirm the idea. The anti-arthritic effects of cytarabine (cytosine arabinoside, an immunosuppressant drug) also have been studied. Cytarabine has no systemic or local “anti-inflammatory” effect in a variety of experimental assay systems. It inhibits completely the onset of adjuvant arthritis and renders animals tolerant to further adjuvant inoculations. The APR cannot be used exclusively to distinguish between the different steroidal, non-steroidal, and immunosuppressant types of “anti-inflammatory” drugs. They are useful, however, in the overall assessment of the “anti-inflammatory” effects of drugs in all types of inflammation. The APR should be incorporated as standard procedures in laboratories “discovering” new “anti-inflammatory” drugs. Emphasis is placed on the APR as necessary requirements for the assessment of “anti-inflammatory” drugs because for example, Filipin-induced hind-paw edema can be inhibited in vivo by the i.p. administration of digitonin, another lytic agent which produces inflammation.

Anti-inflammatory and PG inhibitory effects of phenacetin and acetaminophen.

Although acetaminophen and phenacetin do not inhibit PG synthesis when added directly to isolated rat platelets and when given orally, both drugs inhibit carrageenan-induced hindpaw edema — a widely used inflammatory assay method. It does not appear that the anti-inflammatory effects of these non-steroidal drugs (unlike other well-known non-steroidal drugs) can be explained on the basis of PG-synthetase inhibition.

Fibrinogen and experimental inflammation

Abstract Plasma fibrinogen concentrations are useful indexes for the assessment of inflammation and its therapy. The increase in plasma fibrinogen concentrations is related to the magnitude of the inflammation. It occurs before clinical evidence of disease. In rats with granuloma pouches, fibrinogen appears to be sequestered in areas of granulomatous tissue formation. Heparin injections into local sites of inflammation lead to exsanguination. Local steroid injections are more efficacious than subcutaneous injections for the reduction of both the local inflammatory reaction and circulating fibrinogen. The exact role of fibrinogen in areas of inflammation is not known entirely. The physiologic factors controlling its increased synthesis by the liver in response to distant sites of inflammation are unknown.

Plasma inflammation units: An objective method for investigating effects of drugs on experimental inflammation

Abstract GLENN et al . have described several simple methods for determining the progress of inflammation in arthritic rats. Among these methods, the plasma inflammation units are the most reproducible. They have been used successfully by both Glenn et al . and Nuss and Winter for the analysis of anti-inflammatory potencies of various steroidal and nonsteroidal drugs. Additional information regarding these simple bioassay methods is discussed in this report.

The pharmacology of 2-(2-fluoro-4-biphenylyl)Propionic acid (Flurbiprofen) A potent non-steroidal anti-inflammatory drug

Flurbiprofen is a potent, orally active, nonsteroidal anti-inflammatory drug in experimental animals. It is less toxic and more potent than indomethacin in certain types of acute and chronic inflammation in the rat. Like indomethacin, flurbiprofen has a prolonged duration of antiinflammatory action. It is effective in all in vitro assay systems used currently for the assessment of other nonsteroidal anti-inflammatory drugs. It is more potent than indomethacin in only one of these in vitro systems, red cell aggregation and sedimentation caused by the addition of dextran. Flurbiprofen may prove to be a useful adjunct for the treatment of various inflammatory diseases in man.

Anomalous biological effects of salicylates and prostaglandins

While some salicylates (salicyclic acid and salicylaldehyde, especially) are as potent as aspirin as acute, orally-active anti-inflammatory drugs in the rat, they are either inactive or far less potent as PG synthesis inhibitors when added directly to isolated platelets or when given orally.Although PGE1 and PGE2 produce anti-ulcerogenic effects when given to rats in the presence of selected nonsteroidal anti-inflammatory drugs, they fail to inhibit the acute anti-inflammatory and anti-nociceptive effects of these drugs. They are anti-inflammatory and anti-nociceptive under certain experimental conditions. PGE1 and PGE2 can also behave as hypothermic agents when given subcutaneously. Related studies, using PG synthesis stimulators in vivo and in vitro (substituted phenylureas), also cause anti-nociception and hypothermia.All of these indirect studies, when taken together, infer that PG synthesis inhibitionper se fails to explain, entirely, the pharmacologic effects of non-steroidal anti-inflammatory drugs. They also suggest that the precise role of certain PGs in toxicopharmacology is far from simple and straightforward.

α-2-GP response in adjuvant-induced polyarthritis: An immunoassay for anti-inflammatory activity

Abstract The responses of plasma inflammation units (P.I. units) and α-2-GP titer were compared in adjuvant induced polyarthritis. These two parameters were also used for determining the anti-inflammatory activity of non-steroids in this connective tissue diasease It was found that, although both parameters can be used in an assay procedure, the α-2-GP parameter is favored when one considers those factors most desirable for the assessment of drug therapy, i.e., the factors of specificity, sensitivity and a wide range of response between high and low values necessary for quantitation. Determination of plasma or serum concentrations of α-2-GP is essentially a simple immunologic procedure utilizing a monospecific antiserum reagent in the agar-gel double diffusion technique of Ouchterlony.

Simple laboratory procedures for the evaluation of topically-active anti-inflammatory drugs

A simple laboratory test for the examination of topically-active steroids and non-steroids is described. The method(s) involves the application of 0.05 ml of 5% croton oil in ethanol or 0.1% H2SO4∶5% croton oil in ethanol to ears of rats. Irritants are allowed to stand at room temperature for 3–4 days. Sulfuric acid, applied alone in cottonseed oil or ethanol, is not inflammagenic but exacerbates the response to croton oil. The resulting inflammation is greater than that which can be elicited by greater concentrations of croton oil. Benzenesulfonic acid acts similarly when added to croton oil. The more intense inflammation elicited by the mixture is less sensitive to ‘non-specific’ drugs.Drugs appearing of interest in preliminary tests, are applied subsequently at equivalent dosages by local application, by application at distant sites and by giving orally to rats with inflammed ears. This routine procedure helps decide if a drug is a topically-active drug exclusively and is acting by only one method of application and/or by two or more; hence, having amixed anti-inflammatory effect.The ear weights of untreated controls (5–10/group) are substracted from irritated ears and the increased weights recorded as ‘milligrams edema’. Hydrocortisone at varying concentrations is used routinely as a ‘positive’ anti-inflammatory control in all routine assays. Differences of inflammatory responses to 5% croton oil and to 0.1% H2SO4∶5% croton oil, as well as individual responses to different drugs given in various ways, are described.Hundreds of compounds (steroidal and non-steroidal) have been tested by the use of these methods.