**2. Adjuvant arthritis: An animal model for preclinical evaluation of new antirheumatics**

In AA the injection of rats with complete or incomplete adjuvant induces polyarthritis, possibly by way of a mechanism involving heat shock proteins. Arthritis induced in rats with intradermal injection of adjuvants containing mycobacteria is an animal model often used for evaluation of potential antirheumatic drugs. This model is also a good methodological tool for investigation of pathological mechanisms in RA. An intradermal injection, into the base of the tail, with heat-killed *Mycobacterium tuberculosis* in incomplete Freund´s adjuvant (IFA) results in destructive arthritis within 14 days in susceptible Dark Agouti or Lewis inbred rat strains. AA can also be induced with cell walls from other bacterial types in IFA, although the arithrogenicity varies (Joe et al., 1999). In many experiments, the induction of arthritis is achieved also with *Mycobacterium butyricum* in IFA (Akiyama et al., 2005; Bauerova et al., 2006, 2009). Basic clinical manifestations of AA are paw swelling, infiltration of mononuclear and polymorphonuclear phagocytes into joints, formation of pannus, periostitis and erosions of cartilage and bone (Williams et al., 1998). The intensity of AA development is described by so-called "basic clinical parameters", i.e. arthritic score, hind paw edema, which are usually measured once a week over the whole duration of the experiment. Increased synthesis of TNF- α, IL-1 and IL-6 is detected as early as day four after adjuvant injection. The disease progresses rapidly over several weeks in what appears clinically to be a monophasic process. Granulocytes and autoreactive CD41

definitely, although they remarkably inhibit the development of arthritis and improve the life quality of patients. Following treatment interruption, a fast development of RA occurs. Biological therapy also has adverse effects, such as development of resistance and secondary infections. For these reasons, the search for new drugs which could avoid these infections or suppress them is still an up-to-date problem. As already mentioned, the most frequently applied conventional drug for RA has been MTX. Its application is usually additional to the biological therapy or it is used in combination with other conventional drugs. Intensive immunosuppressive treatment with MTX or biological therapy adversely affects immunological homeostasis of the organism and increases the risk of infections. For these reasons, there is a search for alternative immunomodulatory approaches, which could minimize side effects of immunosuppressive therapy on cellular and humoral immunity. One possibility is represented by the combination of immunosuppressive and immunostimulatory substances or compounds regulating redox balance of the organism. Their application can establish immunological and redox homeostasis and increase

The focus of this chapter is mostly on substances of natural origin possessing antiinflammatory, antioxidative or immunomodulating properties along with minimal side effects when administered to animals. The safety of long-term therapy of RA is very important, because patients with RA are usually treated for two or more decades. We describe our results obtained in adjuvant arthritis (AA) with endogenous antioxidants as carnosine and coenzyme Q10, glucomannan and Imunoglukan®, as well as selected extracts and compounds from plants. These results will be confronted with results of other authors from preclinical and clinical studies. The aim is to present an overview of the potential of new compounds for the therapy of RA with the focus on approving their ability for

**2. Adjuvant arthritis: An animal model for preclinical evaluation of new** 

In AA the injection of rats with complete or incomplete adjuvant induces polyarthritis, possibly by way of a mechanism involving heat shock proteins. Arthritis induced in rats with intradermal injection of adjuvants containing mycobacteria is an animal model often used for evaluation of potential antirheumatic drugs. This model is also a good methodological tool for investigation of pathological mechanisms in RA. An intradermal injection, into the base of the tail, with heat-killed *Mycobacterium tuberculosis* in incomplete Freund´s adjuvant (IFA) results in destructive arthritis within 14 days in susceptible Dark Agouti or Lewis inbred rat strains. AA can also be induced with cell walls from other bacterial types in IFA, although the arithrogenicity varies (Joe et al., 1999). In many experiments, the induction of arthritis is achieved also with *Mycobacterium butyricum* in IFA (Akiyama et al., 2005; Bauerova et al., 2006, 2009). Basic clinical manifestations of AA are paw swelling, infiltration of mononuclear and polymorphonuclear phagocytes into joints, formation of pannus, periostitis and erosions of cartilage and bone (Williams et al., 1998). The intensity of AA development is described by so-called "basic clinical parameters", i.e. arthritic score, hind paw edema, which are usually measured once a week over the whole duration of the experiment. Increased synthesis of TNF- α, IL-1 and IL-6 is detected as early as day four after adjuvant injection. The disease progresses rapidly over several weeks in what appears clinically to be a monophasic process. Granulocytes and autoreactive CD41

resistance of the organism to infections.

combination therapy with methotrexate.

**antirheumatics** 

cells play major roles in the disease. Humoral immune mechanisms appear not to contribute to the disease process (Joe et al., 1999).

AA has been extensively used for pharmaceutical testing, and therefore much data exists for comparison in humans. While this model does not mimic perfectly the condition of human arthritis, it is easily reproducible, well defined and has proven useful for the development of new therapies for arthritis, as exemplified also by cytokine blockade therapies (Bendele et al., 1999). AA has been used in the evaluation of nonsteroidal inflammatory drugs, such as phenylbutazone and aspirin during the early 1960s, and later COX-2 inhibitors such as celecoxib were studied. AA in rats shares many features with human arthritis, including genetic linkage, synovial CD4+ cells and T cell dependence. On the contrary, one of the major differences between the AA model and human arthritis is simply that the inciting agent is known in the model, though the need for any specific antigen is controversial.
