Comparative study between steroidal and nonsteroidal anti-inflammatory drugs on the mode of their actions on vascular permeability in rat carrageenin-air-pouch inflammation

Pharmaceutical aspects of the recombinant human serum albumin dimer: structural characteristics, biological properties, and medical applications

Human serum albumin is the most abundant protein in the blood. It is clinically used in the treatment of severe hypoalbuminemia and as a plasma expander. The use of albumins as a carrier for drugs is currently being developed, and some are now in the preclinical and clinical trial stages. The main technologies for utilizing an albumin as a drug carrier are protein fusion, polymerization and surface modification, and so on. Among these technologies, albumin dimerization has wide clinical applications as a plasma expander as well as a drug carrier. Despite the fact that many reports have appeared on drugs using an albumin dimer as a carrier, our knowledge of the characteristics of the albumin dimer itself is incomplete. In this review, we summarize the structural characteristics of recombinant albumin dimers produced by two methods, namely, chemical linkage with 1,6-bis(maleimido)hexane and genetically linked with an amino acid linker, and the physicochemical characteristics and biological properties of these preparations. Finally, the potential for pharmaceutical applications of albumin dimers in clinical situations is discussed.

Potential anti-inflammatory actions of the elmiric (lipoamino) acids

A library of amino acid-fatty acid conjugates (elmiric acids) was synthesized and evaluated for activity as potential anti-inflammatory agents. The compounds were tested in vitro for their effects on cell proliferation and prostaglandin production, and compared with their effects on in vivo models of inflammation. LPS stimulated RAW 267.4 mouse macrophage cells were the in vitro model and phorbol ester-induced mouse ear edema served as the principal in vivo model. The prostaglandin responses were found to be strongly dependent on the nature of the fatty acid part of the molecule. Polyunsaturated acid conjugates produced a marked increase in media levels of i15-deoxy-PGJ(2) with minimal effects on PGE production. It is reported in the literature that prostaglandin ratios in which the J series predominates over the E series promote the resolution of inflammatory conditions. Several of the elmiric acids tested here produced such favorable ratios suggesting that their potential anti-inflammatory activity occurs via a novel mechanism of action. The ear edema assay results were generally in agreement with the prostaglandin assay findings indicating a connection between them.

Recombinant Human Serum Albumin Dimer has High Blood Circulation Activity and Low Vascular Permeability in Comparison with Native Human Serum Albumin

PURPOSE

Human serum albumin (HSA) is used clinically as an important plasma expander. Albumin infusion is not recommended for critically ill patients with hypovolemia, burns, or hypoalbuminemia because of the increased leakage of albumin into the extravascular spaces, thereby worsening edema. In the present study, we attempted to overcome this problem by producing a recombinant HSA (rHSA) dimer with decreased vascular permeability and an increased half-life.

METHODS

Two molecules of rHSA were genetically fused to produce a recombinant albumin dimer molecule. The pharmacokinetics and biodistribution of the recombinant proteins were evaluated in normal rats and carrageenin-induced paw edema mouse model.

RESULTS

The conformational properties of this rHSA dimer were similar to those for the native HSA (the HSA monomer), as evidenced by the Western blot and spectroscopic studies. The biological half-life and area under the plasma concentration-time curve of the rHSA dimer were approximately 1.5 times greater than those of the monomer. Dimerization has also caused a significant decrease in the total body clearance and distribution volume at the steady state of the native HSA. rHSA dimer accumulated to a lesser extent in the liver, skin, muscle, and fat, as compared with the native HSA. Up to 96 h, the vascular permeability of the rHSA dimer was less than that of the native HSA in paw edema mouse models. A prolonged plasma half-life of the rHSA dimer was also observed in the edema model rats.

CONCLUSIONS

rHSA dimer has a high retention rate in circulating blood and a lower vascular permeability than that of the native HSA.

Inflammation induced by latex of Calotropis procera--a new model to evaluate anti-inflammatory drugs

Latex of Calotropis procera was studied for its inflammatory reactions using pedal oedema and air pouch models of inflammation in rats. Subcutaneous injection of aqueous solution (0.1 ml of 1%) of dry latex (DL) into the plantar surface of paw produced significant inflammation. Maximum inflammatory response was obtained 1 h after the injection and was maintained for a further 1 h. The inflammatory response was accompanied by an increase in vascular permeability that reached its maximum within 15 min. Inflammation was also induced in the 6-day-old rat air pouch by injecting a 2.5% solution of DL. The latter model was characterized for the exudate volume and its protein concentration, and wet and dry weights of granuloma. A time-course study indicated that both the exudate volume and the weight of granuloma were at maximum on day 5 after DL injection while the protein concentration peaked on the third day. Further, the two models were also studied for the anti-inflammatory effect of various drugs. It was observed that in the pedal oedema model, phenylbutazone was more effective than prednisolone while almost complete inhibition was produced by mepyramine and cyproheptadine. On the other hand, in the air pouch model, prednisolone was more effective than phenylbutazone in inhibiting the inflammation. Thus, the DL-induced inflammation in different models could be used to evaluate anti-inflammatory drugs.

The six-day-old rat air pouch model of inflammation: characterization of the inflammatory response to carrageenan

Inflammation was induced in the 6-day-old rat air pouch by injection of carrageenan. The model was characterized in terms of exudate volume, leucocyte influx, cell free protein, prostaglandin E2 levels, and granuloma formation. The time course of all these inflammatory markers, except prostaglandin E2, showed a 3-hr lag followed by a rapid increase to 8 hr. Thereafter, the rate of increase was much slower to 48 hr. Differential cell counts indicated a predominantly polymorphonuclear cell response (75%) during the first 48 hr. Prostaglandin E2 levels increased rapidly after a 3-hr lag, to a maximum of 440 +/- 140 ng/mL at 15 hr and thereafter quickly declined to 140 +/- 60 ng/mL at 21 hr. Prostaglandin E2 levels were the most sensitive inflammatory marker to (S+)-ibuprofen and were reduced dose dependently in the range 0.05 to 1 mg/kg. We have demonstrated the time course for duration of NSAID-induced reduction of prostaglandin E2 levels during inflammation in an individual animal. Rac-ibuprofen (0.1-1 mg/kg) reduced leucocyte influx at 3 and 5 hr, after which drug effects gradually diminished by 24 hr. Rac-ibuprofen at 1 mg/kg significantly reduced the volume of air pouch exudate recovered at 24 hr but had no effect on protein levels.

Effects of acute and chronic inflammation on the pharmacokinetics of prednisolone in rats

The effects of acute and chronic stages of carrageenan-induced air-pouch inflammation on the pharmacokinetics of prednisolone were studied in male Wistar rats. Chronic inflammation produced a significant increase in the area under the curve (AUC) of prednisolone compared to control animals (6594 +/- 2144 vs 3530 +/- 2164 micrograms.hr/L). The effect of acute inflammation was not significant (AUC = 4996 +/- 3813). Both acute and chronic inflammation also reduced the in vitro plasma protein binding of prednisolone, the reduction being much greater after chronic inflammation. The AUC of free prednisolone after chronic inflammation was 3141 micrograms.hr/L, compared to 1121 micrograms.hr/L in the control group and 1823 micrograms.hr/L after acute inflammation. The mean values of half-life and apparent volume of distribution at steady-state in each group were similar. These results indicate that prednisolone must be used with caution in the treatment of inflammatory diseases because of higher free concentrations of the steroid.

Selective inhibition of NS-398 on prostanoid production in inflamed tissue in rat carrageenan-air-pouch inflammation

NS-398 (N-(2-cyclohexyloxy-4-nitrophenyl) methane sulphonamide), a newly synthesized potent non-steroidal anti-inflammatory drug (NSAID) has a much lesser degree of toxicity, as compared with presently available NSAIDs. We have investigated the inhibition of prostanoid production in inflammatory exudate, gastric mucosa and renal papillary tissue, following oral administration to carrageenan-air-pouch rats. The ID50 values of NS-398 in the inflammatory exudate, gastric mucosa and renal papillary tissue were 0.18, 62.2 and 261.7 mg kg-1, respectively. In contrast, indomethacin decreased the PGE2 concentration in the inflammatory exudate, gastric mucosa and renal papillary tissue, with the same dose range, the ID50 values being 0.23, 0.14 and 0.15 mg kg-1, respectively. The same tendency was seen for 6-keto-prostaglandin F1 and thromboxane B2. Moreover, NS-398 inhibited excess PGE2 production in inflamed tissue but did not affect physiological production of PGE2 in non-inflamed tissue. Indomethacin, in both inflamed and non-inflamed tissues, inhibited PGE2 production to the same degree. These results indicated that NS-398 has some specificity for inflamed tissue, by inhibiting prostanoid synthesis, and this effect may explain the decreased side-effects of this drug.

Time-course of phospholipase A2, eicosanoid release and cellular accumulation in rat immunological air pouch inflammation

Phospholipase A2 activity in the rat air pouch cavity was determined after induction of a reverse passive Arthus reaction. Time-course of phospholipase A2 activity appeared to correlate with increased prostaglandin E2 levels in inflammatory exudate and with the influx of mononuclear inflammatory cells. Local administration of anti-inflammatory drugs such as dexamethasone, indomethacin, or a PLA2 inhibitor such as p-bromophenacyl bromide significantly inhibited exudate volume, cellular influx, granuloma formation, exudate PGE2 levels and PLA2 activity, to varying degrees. Dexamethasone treatment significantly reduced all parameters determined, whereas p-bromophenacyl bromide had a significant inhibitory effect on PLA2 activity and PGE2 release, and indomethacin only restored PGE2 levels. These results show that PLA2 is neither the only nor the most important factor involved in the development of subchronic inflammation.

Analgesic effect of Ga-Al-As diode laser irradiation on hyperalgesia in carrageenin-induced inflammation

This study concerned the effect of Ga-Al-As diode laser irradiation (780 nm, continuous wave, 31.8 J/s/cm2, spot size od 0.2 mm, 3 minutes/dose) on hyperalgesia induced in the hind paw of rats by injecting carrageenin. The pressure-pain thresholds of hind paws were measured by the Randall-Selitto test for evaluation of hyperalgesia. Two doses of laser irradiation, given to the inflamed region immediately before and after the injection of carrageenin, partially (approximately 50%) inhibited the occurrence of hyperalgesia accompanied with a progression of inflammation. This analgesic effect was equal to that of indomethacin (4 mg/kg, i.o.). In another group, the hyperalgesia was removed almost completely for at least 24 hours by one dose of laser irradiation, which was given 3 hours after the carrageenin injection, whereas the edema was not inhibited. This analgesic effect, however, was partially (approximately 50%) antagonized with a dose of 10 mg/kg (i.p.) of naloxone and totally inhibited with 30 mg/kg. These results suggest that low-power laser irradiation on inflamed regions of carrageenin-treated rats has a marked analgesic effect and that certain mechanisms that are not related to endogenous opioids are involved in a part of the mechanisms of the analgesic effects.

Therapeutic effect of Ga-Al-As diode laser irradiation on experimentally induced inflammation in rats

We produced experimental inflammation models in rats by carrageenin and studied the effect of Ga-Al-As diode laser irradiation (780 nm, continuous wave, 31.8 j/sec/cm2, spot size of 0.2 mm) on inflamed regions compared with those of indomethacin, a potent anti-inflammatory agent. We found that a low-power infrared laser has an anti-inflammatory effect on carrageenin inflammation. A low-power laser inhibits: (1) the increase of vascular permeability during the occurrence of an acute inflammation in the carrageenin-air-pouch model, (2) edema in the acute stage in the carrageenin-paw-edema model, and (3) the granuloma formation in the carrageenin-granuloma model after receiving laser irradiation once daily. In all cases, irradiation for less than 10 min was sufficient to inhibit the inflammation by 20-30%. The inhibitory effect of laser irradiation was not comparable to that of indomethacin (4 mg/kg, i.o.) in the air-pouch model and the paw-edema model, whereas laser irradiation was more potent than that of daily administration of indomethacin (1 mg/kg, i.o.) in the granuloma model. In future studies of the mechanism of laser effect, it should be noted that irradiating a rat twice, before and after the provocation of inflammation, was essential in order to achieve an effective inhibition of paw-edema.

Involvement of arachidonic acid metabolites in increases in vascular permeability in experimental dental pulpal inflammation in the rat

Pulp was experimentally inflamed by applying bacterial lipopolysaccharide (LPS). Changes in arachidonic acid (AA) metabolites were determined by measuring the conversion of exogenously added AA in pulp homogenates. The inflamed pulp produced 12-hydroxy-eicosatetraenoic acid (12-HETE), 6-keto-prostaglandin (PG) F1 alpha greater than PGE2, thromboxane B2 and 11-HETE, which was further identified with high-performance liquid chromatography. The LPS treatment caused a 2.0-fold increase in 12-HETE production at 1 h, a 3.8-fold increase in 6-keto-PGF1 alpha production at 12 h and increases in PGE2 and 11-HETE production of 8.8- and 5.5-fold, respectively, at 24 h. Vascular permeability in the inflamed pulp was measured by quantifying the amount of an extravasated dye; it increased markedly from 6 h and reached a peak at 12 h after the LPS application. When indomethacin (0.3-30 mg/kg, s.c.) was given before LPS, both the production of 6-keto-PGF1 alpha and PGE2 and the increase in vascular permeability were inhibited dose dependently. Exogenously applied PGE2 and PGI2 methyl ester reduced the inhibition of the increase in vascular permeability caused by indomethacin. Thus PGE2 and PGI2 may be involved in increases in vascular permeability in pulpal inflammation.

The effect of dexamethasone on tissue water distribution and proton relaxation in Panc02 tumors

The present experiments were conducted to determine the effects of dexamethasone mediated changes in tumor water distribution on proton relaxation times (T1, T2) in a murine pancreatic adenocarcinoma (Panc02). Spin lattice (T1) and spin-spin(T2) relaxation times were determined by ex vivo methods (10 MHz) and by in vivo imaging techniques (6.25 MHz) at various intervals after single or multiple dexamethasone treatments. In complementary studies, dexamethasone mediated changes in tumor capillary permeability, tumor water distribution, relative tumor blood flow and tumor cell proliferation were also determined. Proton spin lattice (T1) and spin-spin (T2 relaxation times for Panc02 tumors shortened within two hours of a single dexamethasone treatment. The time course and magnitude of this response was dexamethasone dose dependent. The time dependent changes in T1 and T2 after dexamethasone were similar at 10 MHz (ex vivo) and 6.25 MHz (in vivo imaging). Although dexamethasone produced little or no change in total tumor water content and tumor cell proliferation, transient changes in the physiologic distribution of tumor water were clearly demonstrated. The data supports the idea that dexamethasone induced changes in the distribution of tumor water were mediated by changes in capillary permeability and tumor blood flow. These physiologic responses produced serial changes in tumor extracellular extravascular water content that were consistent with the observed changes in tumor T1 and T2. The results from these experiments might imply that therapy associated changes in tumor proton relaxation times may not only reflect changes in tissue water content, but may also reflect physiologic responses which alter the distribution of tissue water and solute.

The inflammatory reaction in an experimental model of open wounds in the rat. The effect of arachidonic acid metabolites

The study concerned the effect of arachidonic acid metabolites on the inflammatory reaction in granulation tissue of open wounds in rats. Metabolites or inhibitors were applied in a wound chamber attached to circular, open, full-thickness skin wounds 5 days post-wounding. The adjacent wound served as control. Blood flow, albumin extravasation and accumulation of polymorphonuclear leucocytes (PMNLs) were measured in the granulation tissue. Prostaglandin E2 (PGE2 5.7 microM) increased blood flow and albumin extravasation by 95 and 16%, respectively, without affecting PMNLs. Leukotriene B4 (LTB4 2.7 microM) increased PMNL accumulation by 142% without altering albumin extravasation. Indomethacin (28 microM, repeatedly) did not affect blood flow or albumin extravasation, but increased PMNL accumulation by 21%. Methylprednisolone (3.3 mM, repeatedly) reduced blood flow and albumin extravasation by 29 and 31%, respectively, without influencing PMNLs. The granulation tissue obviously responds to exogenous PGE2 and LTB4. Endogenous arachidonic acid metabolites seem to play only a minor role in the inflammatory process in this model.

Effects of forskolin analogs, phosphodiesterase inhibitors and 8-bromo cyclic AMP on plasma exudations induced with bradykinin and prostaglandin E1 in rat skin

The effects of forskolin analogs, phosphodiesterase inhibitors and 8-bromo cyclic AMP on plasma exudations induced with bradykinin and prostaglandin E1 in rat skin were investigated using [125I]bovine serum albumin (125I-BSA). Forskolin, forskolin 7-ethyl carbonate and 7-desacetylforskolin, which are potent activators of adenylate cyclase, greatly potentiated the bradykinin-induced plasma exudation and inhibited the prostaglandin E1-induced response. On the other hand, 14,15-dihydroforskolin and 1,9-dideoxyforskolin, which are weak or inactive as activators of adenylate cyclase, did not have any significant effect on bradykinin and prostaglandin E1-induced plasma exudations. The phosphodiesterase inhibitors, ZK 62711, dipyridamole, HL 725, and 3-isobutyl-1-methylxanthine potentiated the bradykinin-induced plasma exudation and inhibited the prostaglandin E1-induced response. Papaverine had biphasic effects on the bradykinin-response and slight inhibitory effects on the prostaglandin E1-response. 8-Bromo cyclic AMP in the doses of 0.01 to 1 microgram potentiated the bradykinin-induced plasma exudation, but had no effect at doses of 10 and 100 micrograms. 8-Bromo cyclic AMP at all doses significantly inhibited the prostaglandin E1-induced response. The results suggest that the effects of forskolin and its analogs on plasma exudations induced with bradykinin and prostaglandin E1 in rat skin derive from activation of cyclic AMP-generating systems.

Effect of forskolin on alterations of vascular permeability induced with bradykinin, prostaglandin E1, adenosine, histamine and carrageenin in rats

The effect of the diterpene forskolin on vascular permeability alone and in combination with bradykinin, prostaglandin E1, adenosine or histamine has been investigated in rats. Vascular permeability in rat skin was measured using [125I]-labelled bovine serum albumin ([125I]BSA) as a tracer. In addition, the effect of forskolin on footpad edema induced by the injection of a mixture of 2% carrageenin was determined. Forskolin caused a marked potentiation of the increase in vascular permeability in rat skin elicited by the intradermal injection of histamine or bradykinin. However, forskolin caused a significant suppression of the prostaglandin E1-induced vascular permeability response and at a low concentration suppressed the response to adenosine. Forskolin greatly potentiated the footpad edema induced with carrageenin in rats. Intravenous administration of the enzyme bromelain, which reduces plasma kininogen levels, inhibited the footpad edema induced with carrageenin or with a mixture of carrageenin and forskolin. Parenteral administration of a prostaglandin synthetase inhibitor, indomethacin, suppressed the footpad edema induced with carrageenin, but did not inhibit the footpad edema induced with a mixture of carrageenin and forskolin. An antihistamine, cyproheptadine, had no effect on carrageenin-induced footpad edema either in the presence or absence of forskolin. These results suggest that both bradykinin and prostaglandins are essential for the development of carrageenin-induced footpad edema and that bradykinin plays an important role in the potentiative effect of forskolin on footpad edema induced with carrageenin in rats.

Phospholipase A2 activity in carrageenin-induced inflammatory tissue of rats

Phospholipase A2 activity was detected in 7-day-old carrageenin-induced inflammatory tissue of rats using a synthetic substrate. 1-acyl-2-[3H]arachidonyl-phosphatidylcholine. The inflammatory tissue was homogenized in saline containing 1 M KCl, and the 105,000 g supernatant fraction was placed on a Sephadex G-100 column. The partially purified phospholipase A2 had a pH optimum at 6-7 and was Ca2+ dependent. p-Bromophenacyl bromide was strongly inhibitory to the partially purified phospholipase A2 (IC50 = 1.44 x 10(-5) M). A moderate inhibition was observed with indomethacin. Cycloheximide and dexamethasone, which inhibit prostaglandin production in inflammatory tissue, exerted no direct inhibitory action on the phospholipase A2. There were no direct inhibitory effects of quinacrine, bradykinin, or actinomycin D. The cell-free supernatant fraction of the inflammatory exudate of 7-day-old carrageenin-induced granulation tissue was found to have no phospholipase A2 activity.

Suppression by dexamethasone of vascular permeability responses induced with leukotrienes C and D in the rat skin

The present experiment was designed to investigate whether glucocorticoids counteract proinflammatory action of leukotrienes C and D which were suggested to play an important role as mediators in the inflammatory exudate response. Vascular permeability was measured using 131I-labeled human serum albumin (131I-HSA) as a tracer. The vascular permeability was elevated promptly after intradermal injection of chemically synthesized leukotriene C or D and then rapidly fell down to the control level. A positive dose-response relationship was observed in the dose levels of 0.01-1 microgram of leukotrienes. Dexamethasone at doses of 0.15, 0.5 and 1.5 mg/kg caused dose-dependent suppression of vascular permeability response induced with leukotrienes C and D. The present data indicate that glucocorticoids are capable of exerting direct inhibitory effect against proinflammatory action of leukotrienes C and D produced through phospholipase A2-arachidonate-lipoxygenase pathway.

Prostaglandin production by minced carrageenin granuloma tissue of rats and its inhibition by dexamethasone and cycloheximide

Seven-day-old carrageenin granuloma tissue of rats, when incubated in organ culture, produced 6-keto-prostaglandin F1 alpha, prostaglandin E2, prostaglandin F2 alpha, and thromboxane B2 in ratios of 16/7/1/1, respectively. Indomethacin (1 microgram/ml) inhibited this cyclooxygenase-mediated arachidonic acid metabolism. Dexamethasone (1 microgram/ml) also inhibited this metabolic cascade. Its inhibitory effect was not immediate; preincubation of the tissue with dexamethasone potentiated its inhibitory effectiveness. Cycloheximide (0.1 to 10 microgram/ml) also inhibited prostaglandin production. The inhibitory mechanism by cycloheximide of prostaglandin production was discussed in relation to that by dexamethasone.