Inhibition of LTB4 binding to human neutrophils by nordihydroguaiaretic acid

In vivo amelioration of endogenous antitumor autoantibodies via low-dose P4N through the LTA4H/activin A/BAFF pathway

Cancer progression is associated with the development of antitumor autoantibodies in patients' sera. Although passive treatment with antitumor antibodies has exhibited remarkable therapeutic efficacy, inhibitory effects on tumor progression by endogenous antitumor autoantibodies (EAAs) have been limited. In this study, we show that P₄N, a derivative of the plant lignan nordihydroguaiaretic acid (NDGA), enhanced the production of EAAs and inhibited tumor growth at low noncytotoxic concentrations via its immunoregulatory activity. Intratumoral injection of P₄N improved the quantity and quality of EAAs, and passive transfer of P₄N-induced EAAs dramatically suppressed lung metastasis formation and prolonged the survival of mice inoculated with metastatic CT26 tumor cells. P₄N-induced EAAs specifically recognized two surface antigens, 78-kDa glucose-regulated protein (GRP78) and F1F0 ATP synthase, on the plasma membrane of cancer cells. Additionally, P₄N treatment led to B-cell proliferation, differentiation to plasma cells, and high titers of autoantibody production. By serial induction of autocrine and paracrine signals in monocytes, P₄N increased B-cell proliferation and antibody production via the leukotriene A4 hydrolase (LTA4H)/activin A/B-cell activating factor (BAFF) pathway. This mechanism provides a useful platform for studying and seeking a novel immunomodulator that can be applied in targeting therapy by improving the quantity and quality of the EAAs.

In vitro effects of eicosanoid synthesis inhibitors in the presence of linoleic acid on MDA-MB-231 human breast cancer cells

We investigated the effects of cyclooxygenase and lipoxygenase inhibitors in the presence of linoleic acid (LA), as well as the direct effects of prostaglandin E (PGE) and leukotriene B (LTB) on a human breast cancer cell line (MDA-MB-231) in vitro. Piroxicam, esculetin, and nordihydroguaiaretic acid (NDGA) suppressed cell growth and thymidine incorporation. However, a low concentration (1 microgram/ml) of indomethacin (INDO) stimulated cell growth and thymidine incorporation, while a high concentration of INDO (30 micrograms/ml) inhibited both. Esculetin and NDGA reduced the secretion of LTB, whereas piroxicam reduced the secretion of PGE. INDO reduced the secretion of PGE, but a low concentration of INDO increased the secretion of LTB. Consequently, cell growth was correlated with the PGE and/or LTB concentrations when the cells were treated with these cyclooxygenase or lipoxygenase inhibitors. On the other hand, exogenous PGE2 partially reversed the inhibition of thymidine incorporation caused by INDO, whereas LTB4 exerted a similar effect in the case of esculetin or NDGA. The reversibility of the piroxicam effect with PGE2 is not convincing. Therefore, it is suggested that the growth of MDA-MB-231 cells in vitro is affected by both the lipoxygenase and cyclooxygenase products, probably the other eicosanoids rather than PGE2 and LTB4.

NPC 15669, an inhibitor of neutrophil recruitment, is efficacious in acetic acid-induced colitis in rats

BACKGROUND

The efficacy of the leukocyte recruitment inhibitor, N-[9H-2,7-dimethylfluoren-9-ylmethoxy)carbonyl]-L-leucine (NPC 15669) was compared with drugs used to treat inflammatory bowel diseases in a rat model, acetic acid-induced colitis.

METHODS

Colonic damage assessed by visual inspection, histological quantitation of tissue injury, vascular permeability, myeloperoxidase (MPO) accumulation, and synthesis of inflammatory mediators were measured.

RESULTS

Intrarectal pretreatment with NPC 15669 results in a significant reduction of all measured indices of inflammation. The median effective dose (ED50) of NPC 15669 for inhibition of MPO accumulation and vascular permeability is 13.2 mg/kg and 31 mg/kg, respectively. The active moiety of sulfasalazine, 5-aminosalicylic acid (5-ASA), the antioxidant/5-lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA) and the corticosteroids dexamethasone and hydrocortisone, yielded ED50 values (MPO accumulation) of 68 mg/kg, 95 mg/kg, 0.7 mg/kg, and 13 mg/kg, respectively. When formulated suspensions of NPC 15669, 5-ASA, or dexamethasone were used, potency was increased 10-40-fold. Furthermore, NPC 15669 (10 mg/kg) administered 7 hours after acetic acid and evaluated 24 hours after acetic acid administration significantly attenuated neutrophil influx (70% inhibition of MPO accumulation), whereas 5-ASA (100 mg/kg) displayed no therapeutic effects.

CONCLUSIONS

NPC 15669 may be useful in the treatment of inflammatory disorders.

Antiinflammatory effects of various drugs on acetic acid induced colitis in the rat

The efficacy of various drugs used to treat ulcerative colitis, (sulfasalazine, 5-aminosalicylate, hydrocortisone) was investigated in a model of acetic acid-induced colitis in the rat. Subsequently, we tested the ability of antioxidant/5-lipoxygenase inhibitors (gossypol and nordihydroguiaretic acid [NDGA]) and a cyclooxygenase inhibitor (indomethacin) to attenuate the macroscopic colonic damage and/or neutrophil influx (myeloperoxidase activity [MPO]) associated with this model of colitis. Oral pretreatment with either sulfasalazine, gossypol, or NDGA significantly decreased colonic MPO activity induced by acetic acid. Intrarectal administration of such drugs resulted in an even larger reduction of the colonic inflammation, with gossypol being the most potent compound. Oral or intrarectal administration of corticosteroids (dexamethasone, hydrocortisone) also attenuated the parameters of acetic acid induced colitis. In contrast, pretreatment with indomethacin was ineffective, or when administered daily after colitis induction, indomethacin actually increased colonic neutrophil influx significantly. Our data suggest that both the route of drug administration and dosing regimen employed affect the antiinflammatory potency and/or efficacy of compounds on colitis induced by acetic acid in the rat. Drugs which were effective against this colitis may act by scavenging of oxygen derived free radicals.

IL-1 dependent model of inflammation mediated by neutrophils

Interleukin-1 (IL-1) mediates a number of immunologic and physiologic responses associated with inflammation. A new model to monitor the primary effects of IL-1 and potential inhibitors on inflammation has been developed, which involves unilateral injection of 300 U of highly purified recombinant human IL-1 in mouse ears. Ear thickness of IL-1 injected ears increased 7-10-fold 24 hr posttreatment, concomitant with a corresponding increase in myeloperoxidase activity, suggesting that neutrophil influx contributes to this response. Administration of nonsteroidal antiinflammatory drugs did not influence the IL-1 effect in vivo. Inhibition of phospholipase A2 activity ameliorated the IL-1 stimulated inflammation; treatment with 10 mg/kg dexamethaxone eliminated approximately 80% of increased myeloperoxidase activity compared to control values. This model provides a well-defined in vivo assay with which to quantify the systemic effects of compounds capable of altering the activity of IL-1, and the data suggest that this mechanism may explain the unique efficacy of steroids as antiinflammatories.

Dapsone inhibits LTB4 binding and bioresponse at the cellular and physiologic levels

Radioligand binding studies using human neutrophils exposed to 10-100 microM dapsone indicated that this anti-inflammatory compound antagonized association of LTB4 (leukotriene B4) with its specific receptor sites. Binding inhibition was manifested in reduced biologic response of the neutrophils as determined in LTB4-stimulated chemotaxis. In addition, a physiologic model of LTB4-dependent inflammation in mice was antagonized by systemic administration of dapsone. These data suggest that inhibition of LTB4 binding may represent the cellular mechanism of action responsible for the anti-inflammatory effects of dapsone.