Impaired suppressor cell activity due to surface sulphydryl oxidation in rheumatoid arthritis

Evaluation of thiol/disulfide homeostasis in rheumatoid arthritis and disease activity

BACKGROUND

It has been suggested that the deterioration in the antioxidant defense system due to thiols may cause the pro-oxidant/antioxidant imbalance seen in rheumatoid arthritis (RA). This study was conducted to evaluate thiol/disulfide (-SH/-SS) homeostasis in patients with RA compared to healthy controls, and to validate the limited number of studies examining the relationship between Disease Activity Score-28 (DAS28) and thiol parameters.

METHOD

A total of 100 individuals (mean age: 46.3 ± 12.03) consisting of 86 females and 14 males were included in the RA group, and a total of 100 individuals (mean age: 43.3 ± 10.96 years) consisting of 78 females and 22 males were included in the control group. DAS28 was used to assess RA disease activity. -SH/-SS homeostasis parameters were measured using the automated spectrophotometric method described by Erel and Neselioğlu.

RESULTS

While native thiol (-SH) (p:0.001), total thiol (-SH + -SS) (p < 0.0001) levels and -SH\(-SS + -SH) ratio (p: 0.018) were lower in the RA group compared to the healthy controls, disulfide (-SS) level (p: 0.005)), -SS\-SH (p: 0.001) and -SS\(-SS + -SH) (p: 0.002) ratios were found to be higher. In the control group and the group in remission (defined by DAS28 < 2.6), the median values of -SH (p:0.002) and -SS + -SH (p:0.0008) were found to be significantly higher, and the median value of -SS (p: 0.001) was found to be lower compared to the other DAS28 groups. While a negative correlation was found between DAS28 and -SH (r: -0.243, p: 0.007), a positive correlation was found between DAS28 and -SS (r: 0.316, p: 0.0003), -SS\-SH (r:0.229, p: 0.002) and -SS\(-SS + -SH) (r: 0.285, p: 0.0009).

CONCLUSIONS

The plasma thiol antioxidant pool was decreased in RA compared to healthy controls and those with active disease compared to those in remission.

Potential alteration of tumor microenvironments by β-mercaptoethanol

The therapeutic effectiveness of immune checkpoint inhibitors in cancer patients is quite profound. However, it is generally accepted that further progress is curtailed by accompanying adverse events and by low cure rates linked to the tumor microenvironment. The multitudes of immune processes altered by low-molecular-weight thiols published over the past decades suggest they have potential to alter tumor microenvironment processes which could result in an increase in immune checkpoint inhibitor survival rates. Based on one of the most studied and most potent low-molecular-weight thiols, β-mercaptoethanol (BME), it is proposed that clinical assessment be undertaken to identify any BME benefits with relevance for proliferation/differentiation of immune cells, lymphocyte exhaustion, immunogenicity of tumor antigens and inactivation of suppressor cells/factors. The BME alterations projected to be most effective are: maintenance/replacement of glutathione in lymphocytes via facilitation of cysteine uptake, inhibition of suppressor cells/soluble factors and inactivation of free-radical, reactive oxygen species.

The autoimmune-associated genetic variant PTPN22 R620W enhances neutrophil activation and function in patients with rheumatoid arthritis and healthy individuals

OBJECTIVES

A genetic variant of the leukocyte phosphatase PTPN22 (R620W) is strongly associated with autoimmune diseases including rheumatoid arthritis (RA). Functional studies on the variant have focussed on lymphocytes, but it is most highly expressed in neutrophils. We have investigated the effects of the variant on neutrophil function in health and in patients with RA.

METHODS

Healthy individuals and patients with RA were genotyped for PTPN22 (R620W) and neutrophils isolated from peripheral blood. Neutrophil adhesion and migration across inflamed endothelium were measured. Calcium (Ca(2+)) release and reactive oxygen species (ROS) production in response to fMLP stimulation were also assessed.

RESULTS

Expression of R620W enhanced neutrophil migration through cytokine activated endothelium (non-R620W=24%, R620W=45% migrating cells, p<0.001). Following fMLP stimulation, neutrophils that were heterozygous and homozygous for R620W released significantly more Ca(2+) when compared to non-R620W neutrophils, in healthy individuals and patients with RA. fMLP stimulation, after TNF-α priming, provoked more ROS from neutrophils heterozygous for R620W in patients with RA (non-R620W vs R620W=∼1.75-fold increase) and healthy individuals (non-R620W vs R620W=fourfold increase) and this increase was statistically significant in healthy individuals (p<0.001) but not in patients with RA (p<0.25).

CONCLUSIONS

Expression of PTPN22 (R620W) enhanced neutrophil effector functions in health and RA, with migration, Ca(2+) release and production of ROS increased. Neutrophils are found in large numbers in the RA joint, and this hyperactivity of R620W cells may directly contribute to the joint damage, as well as to the initiation and perpetuation of the chronic immune-mediated inflammatory processes driving the disease.

Increased oxidative stress in patients with familial Mediterranean fever during attack period

OBJECTIVES

We aimed to investigate the status of oxidant and antioxidants during attack period (AP) and attack free periods (AFP) in Familial Mediterranean fever (FMF) patients.

METHODS

Measured the levels of malondialdehyde (MDA), protein carbonyl (PC), glutathione (GSH) and antioxidant vitamins (A,C and E) as well as the activities of catalase (CAT) and glutathione peroxidase (GSH-Px) in serum and whole blood of FMF patients in FMF-AP and FMF-AFP.

RESULTS

Levels of MDA and PC were found significantly higher (p <0.05) both in serum and whole blood of FMF-AP group compared with other groups. The CAT and GSH-Px activities in FMF-AP group were found markedly lower (p <0.05) comparing to HC group. However, there were no statistically significant differences between the groups in terms of antioxidant vitamin levels.

CONCLUSIONS

Our study demonstrated increased oxidative stress in patients with FMF during AP. Investigations are needed to establish the effect of antioxidant supplementation on FMF attack frequency and severity. We also suggest that these increased MDA and PC levels and decreased antioxidants may be used as supportive markers to differentiate AP from AFP. These conclusions need to be validated in further multicenter studies with high number of FMF patients.

Obesity, longevity, quality of life: alteration by dietary 2-mercaptoethanol

Previous investigations demonstrated that optimization of murine immunological reactivity in tissue culture required a sulfhydryl compound; the most effective being 2-mercaptoethanol (2-Me). Since these reports, 2-Me was found beneficial for both growth/function of other cell-types in vitro, including those of other species, and when fed orally, it impeded and/or reversed some in situ physiological changes associated with aging. More recently, thiol-containing compounds possessing oxidation-reduction potentials weaker than 2-Me were found to impart beneficial effects for many other, including human, diseases. Based on these effects, the research herein addressed the question: What consequences might dietary 2-Me impart on health and disease of mice other than those associated with aging? The main parameters monitored over the lifetime of individual animals exposed to dietary 10⁻³ M 2-Me in their drinking water were: quality of life (obesity and development of recumbent, emaciated and/or cachectic health); longevity; and appearance of tumors. Instead of anticipated toxic attributes, the following unique benefits were found; mean survival of a moderately-lived strain (A/J) was increased 40.8%, high-fat-diet obesity was curtailed in C57BL/10 mice, and a goal of aging intervention protocols, namely preventing loss of quality of life during aging (recumbent, emaciated and/or cachectic) was achieved. Various mechanisms are discussed as they pertain to these findings.

Coumarin Schiff-bases: As Antioxidant and Possibly Anti-inflammatory Agents

Coumarin Schiff-bases (CSB) possessing different substituents on the 4-methyl-2-substituted phenyl imino-2H-chromene-7-ol molecule were evaluated for their in-vitro antioxidant and plausible anti-inflammatory potential. The antioxidant studies of selected CSB were carried out by determining their reducing power, OH* radical scavenging activity, scavenging of stable 2,2-diphenyl-l-picrylhydrazine (DPPH*) radical and inhibition of the polyphenol oxidase (PPO) enzyme. The assessment of possible anti-inflammatory potential was performed by trypsin inhibition assay and inhibition of beta-glucuronidase. All the CSBs under study showed significant reducing effects. The majority of the tested CSB were found to be effective scavengers of DPPH* radical with moderate to low OH* scavenging ability and significantly inhibited the activity of PPO. With few exceptions, results from the inhibition assay of trypsin and beta-glucuronidase were not encouraging, however they may be helpful in defining structure-activity relationships in further optimization of the lead molecules.

Analysis of the thiol status of peripheral blood leukocytes in rheumatoid arthritis patients

Although the exact etiology of rheumatoid arthritis (RA) remains unknown, there is increasing evidence that reactive oxygen species and a pro-oxidant/antioxidant imbalance are an important part of the pathogenesis of joint tissue injury. Flow cytometry was used to evaluate the thiol status [surface-thiols and intracellular glutathione (iGSH)] of leukocytes from RA patients and controls. Levels of surface-thiols and iGSH of leukocytes from RA patients were significantly lower than of leukocytes from controls. CD53, a glycoprotein of the tetraspanin superfamily, which coprecipitates with the GSH recycling enzyme gamma-glutamyl transpeptidase, was elevated significantly on leukocytes from RA patients compared with leukocytes from controls. Surface-thiols and GSH play important roles in redox buffering of cells, providing protection from oxidative stress. The chronic inflammation of RA has been associated with oxidative stress, which is shown to cause a decline in the levels of cellular antioxidant sulfhydryls (R-SH). As antioxidant-protective levels also decline with age, the problem is compounded in older RA patients, who did have fewer R-SH. Chronic stress can also have an effect on telomere lengths, determining cell senescence and longevity. Although telomeres shorten with increasing age, our flow cytometry studies indicate that accelerated shortening in telomere lengths occurs with increasing age of RA patients, suggesting premature cellular aging. The paradox is that lymphocytes from RA patients are believed to resist apoptosis, and we suggest that the elevated expression of CD53, which results from the increased oxidative stress, may protect against apoptosis.

Evaluation of nitrosative and oxidative stress in Behcet disease

Plasma nitrotyrosine and nitrite/nitrate levels as markers of nitrosative stress and plasma malondialdehyde (MDA) and protein carbonyl as markers of oxidative stress were determined in patients with Behcet disease (BD). To evaluate the balance between oxidant and antioxidant systems in these patients, we measured erythrocyte lysate CuZn superoxide dismutase (CuZn SOD) activity, plasma sulfhydryl (SH) values and total antioxidant activity. We also determined levels of plasma C-reactive protein (CRP), a key marker of inflammation, and compared them with those of healthy subjects. We found plasma nitrotyrosine levels of BD patients to be increased, indicating that nitrosative stress may occur in these patients. Plasma MDA and CRP levels in BD patients were found to be significantly higher than those in control group. However, plasma SH levels were decreased. No changes were observed in the other measured parameters of the patient group compared with the controls. These data suggest the possible involvement of nitric oxide (NO) together with reactive oxygen substances (ROS) in the pathogenesis of BD.

Antioxidants and fatty acids in the amelioration of rheumatoid arthritis and related disorders

The generation of reactive oxygen species (free radicals) is an important factor in the development and maintenance of rheumatoid arthritis in humans and animal models. One source of free radicals is nitric oxide produced within the synoviocytes and chondrocytes and giving rise to the highly toxic radical peroxynitrite. Several cytokines, including tumour necrosis factor-alpha (TNFalpha) are involved in the formation of free radicals, partly by increasing the activity of nitric oxide synthase. Indeed, nitric oxide may mediate some of the deleterious effects of cytokines on bone resorption. Aspirin, tetracyclines, steroids and methotrexate can suppress nitric oxide synthase. Dietary antioxidants include ascorbate and the tocopherols and beneficial effects of high doses have been reported especially in osteoarthritis. There is also evidence for beneficial effects of beta-carotene and selenium, the latter being a component of the antioxidant enzyme glutathione peroxidase. The polyunsaturated fatty acids (PUFA) include the n-3 compounds, some of which are precursors of eicosanoid synthesis, and the n-6 group which can increase formation of the pro-inflammatory cytokines TNFalpha and interleukin-6, and of reactive oxygen species. Some prostaglandins, however, suppress cytokine formation, so that n-3 PUFA often oppose the inflammatory effects of some n-6-PUFA. gamma-linolenic acid (GLA) is a precursor of prostaglandin E1, a fact which may account for its reported ability to ameliorate arthritic symptoms. Fish oil supplements, rich in n-3 PUFA such as eicosapentaenoic acid have been claimed as beneficial in rheumatoid arthritis, possibly by suppression of the immune system and its cytokine repertoire. Some other oils of marine origin (e.g. from the green-lipped mussel) and a range of vegetable oils (e.g. olive oil and evening primrose oil) have indirect anti-inflammatory actions, probably mediated via prostaglandin E1. Overall, there is a growing scientific rationale for the use of dietary supplements as adjuncts in the treatment of inflammatory disorders such as rheumatoid arthritis and osteoarthritis.

Lymphoma in patients with rheumatoid arthritis: association with the disease state or methotrexate treatment

Although long-term clinical studies have shown no excessive risk of lymphoma in rheumatoid arthritis (RA) patients treated with methotrexate (MTX), an increasing number of reports of this association continue to appear. We describe two cases, review the cases in the world's literature, and summarize their important characteristics. Possible oncogenic mechanisms are discussed. Most lymphoproliferation cases presented here have features of immunosuppression-associated lymphoma. The immunosuppressed state is attributable to a combination of factors, such as RA itself and the actions of MTX. The risk factors for RA patients to develop lymphoma while on MTX include severe disease, intense immunosuppression, genetic predisposition, and an increased frequency of latent infection with prooncogenic viruses such as Epstein-Barr virus (EBV). The spontaneous remission of lymphomas in eight RA patients after MTX was stopped highlights the likely causative role of the drug in the development of these malignancies. If the clinical situation permits, a period of observation for spontaneous remission after MTX is stopped is advisable. The physicians caring for RA patients on MTX should maintain a high surveillance for signs and symptoms suggestive of lymphoma.

Laboratory findings and pathology of psoriatic arthritis

Over recent years there has been a great deal of interest in the immunology, molecular biology and pathology of psoriasis and PsA. The pathogenetic mechanisms in PsA are less well understood than those described for psoriasis. There are almost certainly genetic and immune components. What is not clear is whether there is a primary immune defect or whether unknown stimuli lead to the recruitment of the immune system and establishment of the disease; nor is it absolutely clear whether PsA is an extension of psoriasis in certain prone individuals. Vascular abnormalities are the earliest histopathological changes to occur in the psoriatic plaque and are also prominent in the psoriatic synovium. Espinoza et al (1982) have suggested there may be a primary vascular defect in PsA. The fact that vascular changes occur before infiltration of immunocompetent cells and are the first changes to resolve with treatment of psoriasis is likely to be significant. Abnormalities in the cellular kinetics and growth factor sensitivity of keratinocytes, fibroblasts and synoviocytes have been highlighted previously. The ability of these cells to produce growth factors and express HLA class II antigens demonstrates the potential for them to initiate and maintain inflammation. The development and possible increased incidence of PsA in patients with such profound immunodeficiency as acquired immune deficiency syndrome suggests that T helper cells do not play a significant role in the establishment of the disease (Arnett et al, 1991). Previously, many immune changes were described. Unfortunately they are non-specific and do not indicate a fundamental defect or marker of PsA. Vasey (1985) has suggested that insidious exposure to Gram-positive bacteria from the gut, tonsils and psoriatic plaques results in chronically stimulated monocytes, macrophages and dendritic cells. These cells are able to migrate throughout the body. Repeated microtrauma may result in the homing of these cells to sites of injury in the skin, synovium and tendons. Interaction with genetically hyperactive synoviocytes and keratinocytes with concomitant release of growth factors may precipitate early lesions of psoriasis and PsA. This hypothesis needs to be substantiated, but it ties together some of the varying observations seen. Many abnormal laboratory findings have been described. Unfortunately, none of the serological changes is sufficiently specific to be of great help in diagnosis. CRP levels and the ESR remain the best promise as markers of the inflammatory component of the arthritis, while other indicators correlate with certain facets of the disease pathology, but as yet have not found a true niche in the management of PsA.(ABSTRACT TRUNCATED AT 400 WORDS)