**1. Introduction**

96 Rheumatoid Arthritis – Etiology, Consequences and Co-Morbidities

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Fraser, J.K., Benhaim, P., & Hedrick, M.H. (2002). Human adipose tissue is a source

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Joint diseases cause serious medical problems for several million people world-wide and therefore the World Health Organization has designated years 2000-2010 as the Decade of the Bone and Joint (Popko et al.2011).

Osteoarthritis (OA) is the most common, and increasingly prevalent, human joint disorder (Dieppe, 2000). It has been estimated that in 1990 12 % of Americans, nearly 21 million people had clinical symptoms of osteoarthritis (Lawrence et al., 1998).

Rheumatoid arthritis (RA) affects about 0.3 to 1.5% of the world population(Chikanza et.al., 1998). Juvenile idiopatic arthritis (JIA) is one of the most common rheumatic diseases in children, which causes pain and functional disability. According to a 2008 study performed by the National Arthritis Data Workgroup, there were close to 3000,000 children in the U.S.A. with some form of juvenile arthritis (Giannini et al., 2010).

Lyme arthritis (LA) caused by spirochete Borrelia burgdorferi, is increasing in prevalence disease involving the musculoskeletal system, particularly affecting knee joints (Pancewicz et. al.2009).

RA and JIA are chronic autoimmune inflammatory diseases primarily affecting the synovial membrane, leading to joint damage and destruction. OA is the most common joint disorder and a major public health problem in western populations (Lawrence et al. 1998).

Clinical and epidemiological studies on OA have recognized a series of etiologic factors including local factors (such as malformations or joint injuries) and systemic factors (such as overweight, race, gender, or metabolic diseases). OA is associated with a loss of proper balance between synthesis and degradation of the macromolecules that gives articular cartilage its biomechanical and functional properties. Concomitantly in OA, changes occur in the structure and metabolism of the synovium and subchondral bone of the joint.

### **2. Degradation of human articular cartilage**

Progressive destruction of articular cartilage is a common feature of OA, RA, and LA. The articular cartilage from patients with OA and RA has decreased concentrations of proteoglycans and glycosaminoglycans (GAGs), and the size of GAG molecules is also

Lysosomal Glycosidases in Degradation of Human Articular Cartilage 99

as in GM2 gangliosidases ( Zwierz et al. 1999; Pennybacker et al. 1996; Sharma et al. 2003; Itakura et al. 2006 ). β-galactosidase (GAL) releases terminal galactose (Czartoryska 1977), from the non reducing terminal of oligosaccharide chains of glycoproteins, glycolipids and keratan sulfate. Mannose is liberated from N-linked sugar chains of glycoproteins, as well as a variety of synthetic and natural β-mannosides, by α-mannosidase (MAN) (Czartoryska 1977). Lysosomal α-fucosidase (FUC) ) (Li,C.,Qian et al. 2006) is involved in the degradation a variety of fucose-containing oligosaccharide chains of glycoproteins and glycolipids and βglucuronidase (GluA) cleaves glucuronic acid residues from the non-reducing terminal of

N-acetyl-β-hexosaminidase (HEX), β-glucuronidase (GluA), β-galactosidase (GAL), αmannosidase (α-MAN), and α-fucosidase (FUC). N-acetyl-β-hexosaminidase (EC 3.2.1.52, HEX, NAG) is the most active enzyme of the lysosomal exoglycosidases (Popko et al. 2006). HEX has several isoenzymes: A, B, S, C, I1, I2. HEX A and S are thermolabile and B, P, I1, I2, thermostable. In humans there are two major isoenzymes of hexosaminidase: HEX A (αβ), and HEX B (ββ). Both isoenzymes recognize terminal N-acetylglucosamine and Nacetylgalactosamine, but only HEX A recognizes 6-sulfated residues of these sugars. HEX A represents (an average) 48% of total HEX activity in serum, and 52% of total HEX activity in

The hexosaminidase S (HEX S) is of minor importance, as it constitutes less than 0.02% of HEX activity (Ikonne et al. 1975)), and can be detected in patients with Sandhoff disease (Yamanak et al. 2001). The function of the HEX S is not well understood, but it is probably

The protein moiety of lysosomal exoglycosidases is synthesized in the rough endoplasmic reticulum, and transported to lysosomes thought the endoplasmatic reticulum and Golgi apparatus (Zwierz et al.1999). Some of the lysosomal enzymes are secreted from the cell into the extracellular fluid. Another route for the secretion of lysosomal enzymes is from the lysosomes via the endosomes and Golgi compartment to the cell surface and extracellular fluid. The release of exoglycosidases is regulated by a small Ras-related GTP-binding protein Rho p21 (Rho proteins control the polymerization of actin into filaments and govern the organization of body filaments into specific types of structures). The release of exoglycosidases from mast cells has shown to be induced by an IgE mediated increase in

Exoglycosidases activity of knee synovial fluid and serum of healthy humans is presented in

The exoglycosidases activity, is higher in synovial fluid than in serum. Levels of the HEX activity are constant in serum of healthy humans up to 40 years of age, whereas in older

The substrates for exoglycosidases in articular cartilage include cell surface and extracellular matrix glycoproteins as well as glycosaminoglycans: chondroitin 4-sulfate, chondroitin 6 sulfate, hyaluronic acid, keratin sulfate, and dermatan sulfate (Winchester 1996; Stypułkowska

people (more than 40 years of age) the level of HEX activity significantly increases.

glycosaminoglycans (GAGs) (Marciniak et al. 2006).

synovial fluid (Popko et. al.2006).

involved in the degradation of GAGs.

intracellular Ca²+ (Zwierz et al. 1999).

Fig. 2.

et al. 2004).

**3. The characterization and function of lysosomal glycosidases**  The main exoglycosidases in tissues, serum and synovial fluid of humans are:

reduced (Inerot et al.1978). In established joint disease, loss of articular proteoglycans could be more significant than the collagen loss (Mankin & Lippiello, 1970; Popko et al. 1983). Destruction of articular cartilage is a multifactorial process, which is performed extracellularly by concerted action of matrix metalloproteinases (MMPs) and glycosidases (Fig.1).

Fig. 1. Cartilage destruction by proteases and glycosidases.

Of the metalloproteinases, collagenase (MMP-1) in particular, appears to be responsible for the degradation of interstitial collagens. The gelatinases (MMP-2 and MMP-9) degrade the denatured forms of collagens, acting in synergy with MMP-1. The stromelysins (MMP-3) have broader substrate specificity for non-connective tissue proteins. Membrane-type MMPs (MT-MMP-1 and MT-MMP-3) have been detected at sites of destruction in rheumatoid arthritis (Pap et al., 2000).

Protease action increases the accessibility of cleavage sites for endo- and exoglycosidases (Ortutay et al. 2003) by production glycopeptides (Fig.1).

Endoglycosidases (hyaluronidases, chondroitinases, keratanases,etc.) cleave glycosidic linkages inside glycosaminoglycan or oligosaccharide chains of the proteoglycans or release oligosaccharide chains from protein cores ( Stypułkowska et al. 2004).

In contrast to endoglycosidases, lysosomal exoglycosidases: N-acetyl-β-hexosaminidase (HEX), β-galactosidase (GAL), β-glucuronidase (GluA), α-mannosidase (MAN) and αfucosidase (FUC), release monosaccharides from the non-reducing terminals of oligosaccharide chains of glycoproteins, glycolipids and proteoglycan glycosaminoglycans of synovial tissue, articular cartilage and synovial fluid. N-acetyl-β-hexosaminidase (HEX) is present as two isoenzymes HEX A and HEX B which both release terminal Nacetylhexosamines, whereas HEX A also hydrolyzes hexosamines in acidic oligosaccharides

reduced (Inerot et al.1978). In established joint disease, loss of articular proteoglycans could be more significant than the collagen loss (Mankin & Lippiello, 1970; Popko et al. 1983). Destruction of articular cartilage is a multifactorial process, which is performed extracellularly

Of the metalloproteinases, collagenase (MMP-1) in particular, appears to be responsible for the degradation of interstitial collagens. The gelatinases (MMP-2 and MMP-9) degrade the denatured forms of collagens, acting in synergy with MMP-1. The stromelysins (MMP-3) have broader substrate specificity for non-connective tissue proteins. Membrane-type MMPs (MT-MMP-1 and MT-MMP-3) have been detected at sites of destruction in rheumatoid

Protease action increases the accessibility of cleavage sites for endo- and exoglycosidases

Endoglycosidases (hyaluronidases, chondroitinases, keratanases,etc.) cleave glycosidic linkages inside glycosaminoglycan or oligosaccharide chains of the proteoglycans or release

In contrast to endoglycosidases, lysosomal exoglycosidases: N-acetyl-β-hexosaminidase (HEX), β-galactosidase (GAL), β-glucuronidase (GluA), α-mannosidase (MAN) and αfucosidase (FUC), release monosaccharides from the non-reducing terminals of oligosaccharide chains of glycoproteins, glycolipids and proteoglycan glycosaminoglycans of synovial tissue, articular cartilage and synovial fluid. N-acetyl-β-hexosaminidase (HEX) is present as two isoenzymes HEX A and HEX B which both release terminal Nacetylhexosamines, whereas HEX A also hydrolyzes hexosamines in acidic oligosaccharides

by concerted action of matrix metalloproteinases (MMPs) and glycosidases (Fig.1).

Fig. 1. Cartilage destruction by proteases and glycosidases.

(Ortutay et al. 2003) by production glycopeptides (Fig.1).

oligosaccharide chains from protein cores ( Stypułkowska et al. 2004).

arthritis (Pap et al., 2000).

as in GM2 gangliosidases ( Zwierz et al. 1999; Pennybacker et al. 1996; Sharma et al. 2003; Itakura et al. 2006 ). β-galactosidase (GAL) releases terminal galactose (Czartoryska 1977), from the non reducing terminal of oligosaccharide chains of glycoproteins, glycolipids and keratan sulfate. Mannose is liberated from N-linked sugar chains of glycoproteins, as well as a variety of synthetic and natural β-mannosides, by α-mannosidase (MAN) (Czartoryska 1977). Lysosomal α-fucosidase (FUC) ) (Li,C.,Qian et al. 2006) is involved in the degradation a variety of fucose-containing oligosaccharide chains of glycoproteins and glycolipids and βglucuronidase (GluA) cleaves glucuronic acid residues from the non-reducing terminal of glycosaminoglycans (GAGs) (Marciniak et al. 2006).
