Treatment with anti-gamma-glutamyl transpeptidase antibody attenuates osteolysis in collagen-induced arthritis mice

Gamma-glutamyl transpeptidase and indirect bilirubin may participate in systemic inflammation of patients with psoriatic arthritis

BACKGROUND

Previous studies have suggested that systemic metabolic abnormalities are closely related to psoriatic arthritis (PsA). Gamma-glutamyl transpeptidase (GGT) and indirect bilirubin (IBIL), two essential active substances in hepatic metabolism that have been demonstrated as an oxidative and anti-oxidative factor respectively, have been proved to be involved in oxidative stress damage and inflammation in several human diseases. However, their role in PsA remains unclear.

METHODS

In this retrospective comparative cohort study, a case group of 68 PsA patients and a control group of 73 healthy volunteers from the Third Hospital of Hebei Medical University were enrolled. Serum GGT, IBIL, GGT/IBIL ratio and C-reactive protein (CRP), a well applied bio-marker of systemic inflammatory in PsA, were compared between the two groups. Furthermore, the relationship of GGT, IBIL and GGT/IBIL with CRP were explored in PsA patients. Finally, the patients were divided into high inflammation group and low inflammation group according to the median value of CRP. Multivariate logistic regression analyses were used for the association of systemic inflammation level with GGT, IBIL and GGT/IBIL.

RESULTS

Compared with healthy controls, PsA patients exhibited significantly higher serum GGT, GGT/IBIL, and CRP levels and lower IBIL levels. Serum GGT and GGT/IBIL were positively correlated with CRP, whereas IBIL were negatively correlated with CRP. Binary logistic regression analysis revealed that serum GGT was a risk factor for high CRP in PsA, whereas IBIL was a protective factor. Furthermore, GGT/IBIL was a better indicator of high CRP condition in PsA patients than either GGT or IBIL alone, as determined by the receiver operating characteristic curves.

CONCLUSION

GGT and IBIL may participate in the pathogenesis of PsA. Additionally, GGT, IBIL and the balance of the two may reflect systemic inflammation mediated by oxidative stress events related to metabolic abnormalities to a certain extent.

Enhanced Anti-Inflammatory Effect of the Combination of Lactiplantibacillus plantarum LS/07 with Methotrexate Compared to Their Monotherapies Studied in Experimental Arthritis

The gut microbiome (GM) of rheumatic arthritis (RA) patients is often altered in composition and function. Moreover, methotrexate (MTX), one of the most frequently used disease-modifying antirheumatic drugs, is known to negatively affect GM composition. The modulation of immune system activity is one of the therapeutic benefits of probiotics. The aim of the current investigation was to determine the impact of MTX therapy combined with one of the Lactobacillus strains, Lactoplantibacillus plantarum LS/07 (LB), on adjuvant arthritis (AA) in rats. Methods focused on biometric and inflammatory parameters in AA, particularly on plasmatic levels of IL-17A, MMP-9, and MCP-1, and the activities of gamma-glutamyl transferase in the spleen and joints were applied. Enhancing the effect of MTX, LB positively influenced all biometric and inflammatory parameters. The findings of the present study may be of help in proposing novel therapeutic strategies for RA patients.

Analysis of gamma-glutamyltransferase in acute promyelocytic leukemia patients undergoing arsenic trioxide treatment

OBJECTIVES

The remarkable effect of arsenic trioxide (ATO) was verified, but elevated gamma-glutamyltransferase (GGT), aminotransferases (ALT and AST) are generally observed in acute promyelocytic leukemia (APL) patients undergoing ATO treatment. However, utilization of hepatoprotective agents or discontinuation of ATO may inhibit ATO efficacy. In order to maintain ATO effect from hepatoprotective agents' influence so we investigate relationships between single elevation in GGT and hepatocellular injury in this study.

METHODS

Correlation of GGT variation and leukocyte counts were analyzed in all 81 APL patients, correlations among liver enzymes (ALT, AST and GGT) were also analyzed in patients without prophylactic hepatoprotective agents. In following study, we take the clinical observation of changes in aminotransferases in patients with single elevation in GGT without hepatoprotective agents.

RESULTS

The average elevated GGT in the WBC abnormal group was more than the normal group (53.86U/L vs. 31.03U/L, P = 0.008), a positive Pearson's correlation of GGT variation and changed leukocyte counts in patients without prophylactic hepatoprotective agents. There are no significant correlation between aminotransferases (ALT and AST) and GGT but correlation between ALT and AST was statistically significant (R = 0.649, P = 0.000). For APL patients with single elevation in GGT, ALT and AST levels were normal throughout the ATO treatment without hepatoprotective agents.

CONCLUSION

Single elevation in GGT without elevated aminotransferases can't be identified as hepatotoxicity, and the elevated levels of GGT are associated with increasing leukocyte counts. Continue single-agent ATO without prophylactic hepatoprotective agents is recommended in APL patients with single elevation in GGT, in order to maintain ATO effect.

Bioflavonoid Robinin from Astragalus falcatus Lam. Mildly Improves the Effect of Metothrexate in Rats with Adjuvant Arthritis

Anti-inflammatory potential of orally administrated bioflavonoid-robinin, active sub-stance of original drug Flaroninum™ (FL), was investigated in the combination with methotrexate (MTX) and in monotherapy in rats suffering from adjuvant-induced arthritis (AA). Robinin (kaempferol-3-O-robinoside-7-O-rhamnoside) was isolated from the aerial parts of Astragalus falcatus Lam. The monotherapy with robinin was not efficient in alleviating symptoms of AA. The combination of MTX with robinin was similarly active as MTX alone in reducing the hind paw volume and change of body weight during the whole experiment. The combination, however, reduced plasma levels of Interleukin-17Aand activity of gamma-glutamyl transferase in joint more efficiently then MTX alone. Our results demonstrate that the novel combination of robinin and MTX mildly improved the reduction of inflammation in experimental arthritis.

The dark side of gamma-glutamyltransferase (GGT): Pathogenic effects of an 'antioxidant' enzyme

Having long been regarded as just a member in the cellular antioxidant systems, as well as a clinical biomarker of hepatobiliary diseases and alcohol abuse, gamma-glutamyltransferase (GGT) enzyme activity has been highlighted by more recent research as a critical factor in modulation of redox equilibria within the cell and in its surroundings. Moreover, due to the prooxidant reactions which can originate during its metabolic function in selected conditions, experimental and clinical studies are increasingly involving GGT in the pathogenesis of several important disease conditions, such as atherosclerosis, cardiovascular diseases, cancer, lung inflammation, neuroinflammation and bone disorders. The present article is an overview of the laboratory findings that have prompted an evolution in interpretation of the significance of GGT in human pathophysiology.

γ-Glutamyltranspeptidase is an endogenous activator of Toll-like receptor 4-mediated osteoclastogenesis

Chronic inflammation-associated bone destruction, which is observed in rheumatoid arthritis (RA) and periodontitis, is mediated by excessive osteoclastogenesis. We showed previously that γ-glutamyltranspeptidase (GGT), an enzyme involved in glutathione metabolism, acts as an endogenous activator of such pathological osteoclastogenesis, independent of its enzymatic activity. GGT accumulation is clinically observed in the joints of RA patients, and, in animals, the administration of recombinant GGT to the gingival sulcus as an in vivo periodontitis model induces an increase in the number of osteoclasts. However, the underlying mechanisms of this process remain unclear. Here, we report that Toll-like receptor 4 (TLR4) recognizes GGT to activate inflammation-associated osteoclastogenesis. Unlike lipopolysaccharide, GGT is sensitive to proteinase K treatment and insensitive to polymyxin B treatment. TLR4 deficiency abrogates GGT-induced osteoclastogenesis and activation of NF-κB and MAPK signaling in precursor cells. Additionally, GGT does not induce osteoclastogenesis in cells lacking the signaling adaptor MyD88. The administration of GGT to the gingival sulcus induces increased osteoclastogenesis in wild-type mice, but does not induce it in TLR4-deficient mice. Our findings elucidate a novel mechanism of inflammation-associated osteoclastogenesis, which involves TLR4 recognition of GGT and subsequent activation of MyD88-dependent signaling.

Osteodystrophy in Cholestatic Liver Diseases Is Attenuated by Anti-γ-Glutamyl Transpeptidase Antibody

BACKGROUND

Cholestatic liver diseases exhibit higher levels of serum γ-glutamyl transpeptidase (GGT) and incidence of secondary osteoporosis. GGT has been identified as a novel bone-resorbing factor that stimulates osteoclast formation. The aim of this study was to elucidate the interaction of elevated GGT levels and cholestatic liver disease-induced bone loss.

METHODS

Wistar rats were divided into three groups: sham-operated control (SO) rats, bile duct ligation (BDL) rats, and anti-GGT antibody-treated BDL rats (AGT). Serum GGT level was measured. Bone mineral density (BMD) was analyzed by dual-energy X-ray absorptiometry. Bone morphometric parameters and microarchitectural properties were determined by micro-computed tomography and histomorphometry of the distal metaphysis of femurs. Alterations of bone metabolism-related factors were evaluated by cytokine array. Effects of GGT on osteoblasts or stromal cells were evaluated by RT-PCR, enzyme activity, and mineralization ability.

RESULTS

Serum levels of GGT were significantly elevated in the BDL-group. In the BDL group, BMD, bone mass percentage, and osteoblast number were significantly decreased, whereas osteoclast number was significantly increased. These alterations were markedly attenuated in the AGT group. The mRNA levels of vascular endothelial growth factor-A, LPS-induced CXC chemokine, monocyte chemoattractant protein-1, tumor necrosis factor-α interleukin-1β and receptor activator of nuclear factor-kappa B ligand were upregulated, and those of interferon-γ and osteoprotegerin were downregulated in the GGT-treated stromal cells. Furthermore, GGT inhibited mineral nodule formation and expression of alkaline phosphatase and bone sialo-protein in osteoblastic cells.

CONCLUSION

Our results indicate that elevated GGT level is involved in hepatic osteodystrophy through secretion of bone resorbing factor from GGT-stimulated osteoblasts/bone marrow stromal cells. In addition, GGT also possesses suppressive effects on bone formation. Managing elevated GGT levels by anti-GGT antibody may become a novel therapeutic agent for hepatic osteodystrophy in chronic liver diseases.

Serum γ-glutamyltransferase level is associated with periodontal disease independent of drinking habits in Japanese adults

Background Non-alcoholic fatty liver disease is considered a hepatic manifestation of metabolic syndrome. Periodontal disease is a mild chronic inflammatory disease with systemic effects, and many studies have indicated an association between metabolic syndrome and periodontitis. In the present study, we investigated the relationship between periodontitis and liver biochemical parameters according to alcohol drinking habits through a cross-sectional study based on data from Japanese people in occupational settings. Material and Methods The subjects were 1510 employees (1218 males, 292 females, mean age 50.4 years) who underwent dental and medical checkups in 2012. Associations between the presence of periodontal pockets and serum levels of liver biochemical parameters were assessed. Results Alanine aminotransferase (ALT) and γ-glutamyltransferase (GGT) levels were higher in subjects with than without periodontal pockets. Multiple logistic regression analysis (adjusting for age, gender, cigarette smoking, and alcohol drinking habits, and components of metabolic syndrome) with GGT or ALT as the dependent variable revealed that there was a significant association between periodontal pockets and GGT (odds ratio, OR=1.48), but not ALT. Similar associations were observed when an analysis was performed according to the presence or absence of alcohol drinking habits; the OR was higher in subjects without (OR=1.84) than with drinking habits (OR=1.41). Conclusions The presence of periodontal pockets was associated with serum levels of GGT, a liver biochemical parameter, in Japanese adults with no drinking habit, suggesting that periodontal disease is associated with liver function, independent of alcohol ingestion.

1α,25-Dihydroxyvitamin D3 enhances γ-glutamyl transpeptidase activity in LLC-PK1 porcine kidney epithelial cells

Mammalian γ-glutamyl transpeptidase (GGT) is expressed most highly in the kidney and serves to recover the constituent amino acids of glutathione in the proximal tubules. Serum GGT is used as a marker for obstructive jaundice and alcoholic liver disease and it has been reported that urinary GGT is a potential marker for bone resorption. The present study investigated the effect of derivatives of vitamin D3 on GGT activity in LLC-PK1 porcine renal tubular epithelial cells in order to analyze the biochemical basis of bone metabolism-associated alterations in GGT activity in the kidney. In the presence of 1α,25-dihydroxyvitamin D3 [1,25(OH)2VD3], GGT activity was observed to be significantly increased in LLC-PK1 cells, with an increase in GGT activity also found in the cell medium. While the stimulatory effect of 1-OH-VD3 was similar to that of 1,25(OH)2VD3, vitamin D3 and 25-OH-VD3 had no effect on GGT activity. The increased GGT activity caused by 1,25(OH)2VD3 in LLC-PK1 cells was the result of long-term stimulation of the cells, in contrast to the GGT-induced increase in alkaline phosphatase, which is more transient. Polymerase chain reaction analysis revealed that the 1,25(OH)2VD3‑induced increase in GGT activity was due to prolonged GGT turnover, rather than increased GGT expression, as no increase in GGT mRNA expression was observed. Thus, it is likely that the expression of GGT is not entirely constitutive in the kidney, but is altered under certain conditions, including under hormonal regulation.

Markers of inflammation and oxidative stress studied in adjuvant-induced arthritis in the rat on systemic and local level affected by pinosylvin and methotrexate and their combination

Oxidative stress (OS) is important in the pathogenesis of autoimmune diseases such as rheumatoid arthritis (RA) and its experimental model--adjuvant arthritis (AA). Antioxidants are scarcely studied in autoimmunity, and future analyses are needed to assess its effects in ameliorating these diseases. Although there are studies about antioxidants effects on the course of RA, their role in combination therapy has not yet been studied in detail, especially on extra-articular manifestations of AA. During the 28-d administration of pinosylvin (PIN) in monotherapy and in combination with methotrexate (MTX) to AA rats, we evaluated the impact of the treatment on selected parameters. The experiment included: healthy controls, untreated AA, AA administered 50 mg/kg b.w. of PIN daily p.o., AA administered 0.4 mg/kg b.w. of MTX twice weekly p.o. and AA treated with a combination of PIN+MTX. AA was monitored using: hind paw volume, C-reactive protein, monocyte chemotactic protein-1 (MCP-1), thiobarbituric acid reactive substances (TBARS) and F2-isoprostanes in plasma, γ-glutamyltransferase activity in spleen, activity of lipoxygenase (LOX) in lung, heme oxygenase-1 (HO-1) and nuclear factor kappa B (NF-κB) in liver and lung. PIN monotherapy significantly improved the activation of NF-κB in liver and lung, HO-1 expression and activity of LOX in the lung, MCP-1 levels in plasma (on 14th d) and plasmatic levels of F2-isoprostanes. An important contribution of PIN to MTX effect was the reduction of OS (an increase of HO-1 expression in lung and reduction of plasmatic TBARS) and decrease of LOX activity in the lung.

Pharmacological influence on processes of adjuvant arthritis: Effect of the combination of an antioxidant active substance with methotrexate

Oxygen metabolism has an important role in the pathogenesis of rheumatoid arthritis. A certain correlation was observed between oxidative stress, arthritis and the immune system. Reactive oxygen species produced in the course of cellular oxidative phosphorylation and by activated phagocytic cells during oxidative burst, exceed the physiological buffering capacity and result in oxidative stress. The excessive production of ROS can damage protein, lipids, nucleic acids, and matrix components. Patients with rheumatoid arthritis have an altered antioxidant defense capacity barrier. In the present study the effect of substances with antioxidative properties, i.e. pinosylvin and carnosine, was determined in monotherapy for the treatment of adjuvant arthritis (AA). Moreover carnosine was evaluated in combination therapy with methotrexate. Rats with AA were administered first pinosylvin (30 mg/kg body mass daily per os), second carnosine (150 mg/kg body mass daily per os) in monotherapy for a period of 28 days. Further, rats with AA were administered methotrexate (0.3 mg/kg body mass 2-times weekly per os), and a combination of methotrexate+carnosine, with the carnosine dose being the same as in the previous experiment. Parameters, i.e. changes in hind paw volume and arthritic score were determined in rats as indicators of destructive arthritis-associated clinical changes. Plasmatic levels of TBARS and lag time of Fe²⁺-induced lipid peroxidation (tau-FeLP) in plasma and brain were specified as markers of oxidation. Plasmatic level of CRP and activity of γ-glutamyltransferase (GGT) in spleen and joint were used as inflammation markers. In comparison to pinosylvin, administration of carnosine monotherapy led to a significant decrease in the majority of the parameters studied. In the combination treatment with methotrexate+carnosine most parameters monitored were improved more remarkably than by methotrexate alone. Carnosine can increase the disease-modifying effect of methotrexate treatment in rat AA.

Chondroitin sulfate effect on induced arthritis in rats

OBJECTIVE

Rodent models of osteoarthritis and rheumatoid arthritis are useful tools to study these disease processes. Adjuvant arthritis (AAR) is a model of polyarthritis widely used for preclinical testing of antiarthritis substances. We report the effect of two different doses of highly purified chondroitin sulfate (CS) pharmaceutical grade in the AAR animal model after oral administration.

DESIGN

AAR was induced by a single intradermal injection of heat-inactivated Mycobacterium butyricum in incomplete Freund's adjuvant. The experiments included healthy animals, untreated arthritic animals, arthritic animals having been administered 300 or 900 mg/kg of CS daily, 14 days before AAR induction until the end of the experiment (day 28), arthritic animals having been administered 300 or 900 mg/kg of CS daily, from day 1 until the end of the experiment.

RESULTS

CS was capable of significantly reducing the severity of arthritis along with oxidative stress, a consequence of chronic inflammatory processes occurring in AAR. The CS pre-treatment regimen was effective throughout the whole subacute phase, while treatment from day 1 proved effective only in the chronic period. The effects were confirmed by improved total antioxidant status and γ-glutamyltransferase activity. CS administered under a pre-treatment regimen was also able to reduce the production of pro-inflammatory cytokines, C-reactive protein in plasma, phagocytic activity and the intracellular oxidative burst of neutrophils.

CONCLUSIONS

CS proved to be effective in slowing down AAR development and in reducing disease markers, thus supporting its beneficial activity as a drug in humans.

Oral administration of prostaglandin E(2)-specific receptor 4 antagonist inhibits lipopolysaccharide-induced osteoclastogenesis in rat periodontal tissue

BACKGROUND

Lipopolysaccharide (LPS) from periodontal pathogens is one of the main causes of alveolar bone destruction. Prostaglandin E(2) (PGE(2)) produced by host cells after LPS stimulation may contribute to the bone destruction. PGE(2) regulates osteoblast-mediated osteoclastogenesis via PGE-specific receptor 4 (EP4). We examined the effects of the PGE(2)-EP4 pathway on the expression of osteoclastogenesis-related factors and studied the inhibitory effect of orally administered EP4-specific antagonist (EP4A) on LPS-induced bone destruction compared to complete inhibition of endogenous PGE(2) by indomethacin (IND).

METHODS

ST2 cells were treated with IND or EP4A and stimulated by LPS. The mRNA expressions of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), the receptor activator of nuclear factor-κB ligand (RANKL), and osteoprotegerin in ST2 cells were examined by quantitative reverse transcription-polymerase chain reaction. LPS-induced bone destruction was examined using a rat model for the periodontal tissue destruction with topically applied LPS.

RESULTS

IND and EP4A inhibited the upregulation of TNF-α mRNA expression, and only EP4A inhibited IL-6 and RANKL mRNA expressions in ST2 cells with LPS stimulation. Topically applied LPS induced a two-phase increase in osteoclasts along the alveolar bone margin, peaking after 3 hours and 3 days. Oral administration of EP4A and IND downregulated the later phase increase of osteoclasts. However, the early phase of increase at 3 hours was upregulated in IND-treated rats but not in EP4A-treated rats.

CONCLUSION

It appears that the PGE(2)-EP4 pathway has an important role in LPS-induced osteoclastogenesis, and the specific blocking of the PGE(2)-EP4 pathway by EP4A can effectively downregulate bone destruction caused by LPS without an unexpected increased number of osteoclasts.