Virus-derived anti-inflammatory proteins: potential therapeutics for cancer

Inflammatory responses now have a defined central role in cancer cell growth, invasion, and metastases. Anti-inflammatory proteins from viruses target key stages in immune response pathways and have potential as novel therapeutics for cancer, including highly potent virus-derived inhibitors of protease, chemokine, cytokine, and apoptotic cascades that have been identified. Serine proteases, in addition to their conventional roles in thrombosis, thrombolysis, and apoptotic pathways, are essential regulators of inflammation and are associated with developing cancers. Chemokines drive other inflammatory response pathways with central roles in cell invasion and activation as well as establishing the microenvironment of tumors, modulating immune cell infiltration, cancer cell proliferation, metastasis, and angiogenesis. This review focuses on the mechanisms of action and potential for application of viral immunomodulatory proteins as anticancer therapeutics.     

Cannabinoid-based drugs targeting CB1 and TRPV1, the sympathetic nervous system,and arthritis

Chronic inflammation in rheumatoid arthritis (RA) is accompanied by activation of the sympathetic nervous system, which can support the immune system to perpetuate inflammation. Several animal models of arthritis already demonstrated a profound influence of adrenergic signaling on the course of RA. Peripheral norepinephrine release from sympathetic terminals is controlled by cannabinoid receptor type 1 (CB₁), which is activated by two major endocannabinoids (ECs), arachidonylethanolamine (anandamide) and 2-arachidonylglycerol. These ECs also modulate function of transient receptor potential channels (TRPs) located on sensory nerve fibers, which are abundant in arthritic synovial tissue. TRPs not only induce the sensation of pain but also support inflammation via secretion of pro-inflammatory neuropeptides. In addition, many cell types in synovial tissue express CB₁ and TRPs. In this review, we focus on CB₁ and transient receptor potential vanilloid 1 (TRPV1)-mediated effects on RA since most anti-inflammatory mechanisms induced by cannabinoids are attributed to cannabinoid receptor type 2 (CB₂) activation. We demonstrate how CB₁ agonism or antagonism can modulate arthritic disease. The concept of functional antagonism with continuous CB₁ activation is discussed. Since fatty acid amide hydrolase (FAAH) is a major EC-degrading enzyme, the therapeutic possibility of FAAH inhibition is studied. Finally, the therapeutic potential of ECs is examined since they interact with cannabinoid receptors and TRPs but do not produce central side effects.     

Nitrones as therapeutics

Nitrones have the general chemical formula X-CH=NO-Y. They were first used to trap free radicals in chemical systems and then subsequently in biochemical systems. More recently several nitrones, including alpha-phenyl-tert-butylnitrone (PBN), have been shown to have potent biological activity in many experimental animal models. Many diseases of aging, including stroke, cancer development, Parkinson disease, and Alzheimer disease, are known to have enhanced levels of free radicals and oxidative stress. Some derivatives of PBN are significantly more potent than PBN and have undergone extensive commercial development for stroke. Recent research has shown that PBN-related nitrones also have anti-cancer activity in several experimental cancer models and have potential as therapeutics in some cancers. Also, in recent observations nitrones have been shown to act synergistically in combination with antioxidants in the prevention of acute acoustic-noise-induced hearing loss. The mechanistic basis of the potent biological activity of PBN-related nitrones is not known. Even though PBN-related nitrones do decrease oxidative stress and oxidative damage, their potent biological anti-inflammatory activity and their ability to alter cellular signaling processes cannot readily be explained by conventional notions of free radical trapping biochemistry. This review is focused on our studies and others in which the use of selected nitrones as novel therapeutics has been evaluated in experimental models in the context of free radical biochemical and cellular processes considered important in pathologic conditions and age-related diseases.     

Proteases as therapeutics

Proteases are an expanding class of drugs that hold great promise. The U.S. FDA (Food and Drug Administration) has approved 12 protease therapies, and a number of next generation or completely new proteases are in clinical development. Although they are a well-recognized class of targets for inhibitors, proteases themselves have not typically been considered as a drug class despite their application in the clinic over the last several decades; initially as plasma fractions and later as purified products. Although the predominant use of proteases has been in treating cardiovascular disease, they are also emerging as useful agents in the treatment of sepsis, digestive disorders, inflammation, cystic fibrosis, retinal disorders, psoriasis and other diseases. In the present review, we outline the history of proteases as therapeutics, provide an overview of their current clinical application, and describe several approaches to improve and expand their clinical application. Undoubtedly, our ability to harness proteolysis for disease treatment will increase with our understanding of protease biology and the molecular mechanisms responsible. New technologies for rationally engineering proteases, as well as improved delivery options, will expand greatly the potential applications of these enzymes. The recognition that proteases are, in fact, an established class of safe and efficacious drugs will stimulate investigation of additional therapeutic applications for these enzymes. Proteases therefore have a bright future as a distinct therapeutic class with diverse clinical applications.     

Design of copper-based anti-inflammatory drugs

It has been shown that the inflammation associated with rheumatoid arthritis can be reduced using copper complexes. In order to improve the bioavailability of copper and hence efficacy of these complexes we have synthesized three different series of ligands, each having different characteristics. Thermodynamic results for copper(II) complexes for these polyamino, diaminodiamido and triaminodiamido ligands are presented. The polyamino ligands form the most stable complexes in vivo but tissue distribution studies in mice show that [Cu(3,6,9,12-tetraazatetradecanedioate)] is excreted rapidly, unchanged in the urine. The diamino ligand complexes are much less stable than their polyamino analogues and animal studies using [Cu(N,N'-bis[2-(dimethylamino)ethyl]-ethanediamide)H2] indicate that the complex dissociates in vivo and is excreted slowly via the liver. The triaminodiamido copper(II) complexes are approximately 2 log units more stable than their diamino analogues. Computer simulation calculations indicate that these complexes are also likely to dissociate in plasma. Measured partition coefficients, however, suggest the possibility of dermal absorption.     

Free radicals and anti-inflammatory drugs

It is widely accepted that oxygen radicals and other activated oxygen species are potent mediators or modulators of acute and chronic inflammation. They are common products of cellular metabolism, where their concentrations are controlled by different protective mechanisms such as superoxide dismutase, catalase etc. In addition to their destructive effects on various macromolecules, oxygen radicals or their products are beneficial e.g., in killing bacteria. Oxygen radicals are also closely related to arachidonic acid metabolism, prostanoids (cyclo-oxygenase pathway) and leukotrienes (lipoxygenase pathway) as well as to lipid peroxidation in general. Also, the classical mediators of inflammation, histamine and bradykinin, may be connected with the release of oxygen radicals. In addition to the earlier described inhibition of formation of prostanoids, non-steroidal anti-inflammatory drugs can inhibit production of free radicals or scavenge those already formed. Antirheumatic penicillamine and allopurinol used in the treatment of gout also act on oxygen radicals. New anti-inflammatory compounds with antioxidant properties will be developed in the near future.     

Humanized antibodies as therapeutics

Since 1997, nine humanized antibodies received the approval of the FDA to be used as drugs for the treatment of various diseases including transplant rejections, metastatic breast and colon cancers, leukaemia, non-Hodgkin lymphomas, allergic conditions or multiple sclerosis. This review describes techniques used to engineer these antibodies and presents the recent evolutions of these techniques : SDRs grafting or < abbreviated > CDRs grafting. Based on the illustrative examples of several antibodies, Mylotarg, Herceptin or Xolair, the therapeutic effectiveness of humanized antibodies are underlined and, with the example of Tysabri, the sometimes dramatic adverse effects associated with their clinical use is stressed. In a second part, this review presents some future and realistic avenues to improve the effectiveness of the humanized antibodies, to decrease their immunogenicity and to reduce their cost.     

Tuberculosis and nonsteroidal anti-inflammatory drugs.

In 1980 and 1982 two case reports documented reactivation of pulmonary tuberculosis in patients who had used nonsteroidal anti-inflammatory drugs (NSAIDs). A case-control study was designed to test the hypothesis that such an association does exist. Data for 38 patients were obtained from the patients'' family physicians, and each patient was matched with a control from the same practice for age, sex, race and length of time in that practice. A statistically significant relation was found between the reactivation of tuberculosis and the use of NSAIDs. However, further research is imperative to determine whether the association is direct, indirect or secondary to an unknown factor. Physicians should keep in mind that NSAIDs are potent anti-inflammatory agents and may thus activate, spread and mask infections.     

Carbachol interactions with nonsteroidal anti-inflammatory drugs

The inhibition of cyclooxygenase enzymes by nonsteroidal anti-inflammatory drugs (NSAIDs) does not completely explain the antinociceptive efficacy of these agents. It is known that cholinergic agonists are antinociceptive, and this study evaluates the interactions between carbachol and some NSAIDs. Antinociceptive activity was evaluated in mice by the acetic acid writhing test. Dose-response curves were constructed for NSAIDs and carbachol, administered either intraperitoneally (i.p.) or intrathecally (i.t.). The interactions of carbachol with NSAIDs were evaluated by isobolographic analysis after the simultaneous administration of fixed proportions of carbachol with each NSAID. All of the drugs were more potent after spinal than after systemic administration. The combinations of NSAIDs and carbachol administered i.p. were supra-additive; however, the i.t. combinations were only additive. Isobolographic analysis of the coadministration of NSAIDs and carbachol and the fact that atropine antagonized the synergistic effect suggest that carbachol may strongly modulate the antinociceptive activity of NSAIDs; thus, central cholinergic modulation would be an additional mechanism for the antinociceptive action of NSAIDs, unrelated to prostaglandin biosynthesis inhibition.