Increased expression of multidrug resistance of P-glycoprotein on Th1 cells correlates with drug resistance in rheumatoid arthritis

Th17.1 lymphocytes: emerging players in the orchestra of immune-mediated inflammatory diseases

It is now well established that Th17 lymphocytes associate with myriad immune-mediated inflammatory diseases. Over the past one and a half decades, a subset of Th17 lymphocytes viz. Th17.1 lymphocytes has been identified in pre-clinical and clinical models of inflammatory rheumatic diseases. These lymphocytes secrete IL-17A (signature cytokine of Th17 lymphocytes) as well as IFN-γ (the signature cytokine of Th1 lymphocytes). They express the chemokine markers for Th1 (CXCR3) as well as Th17 (CCR6) lymphocytes. Th17.1 lymphocytes also express the drug efflux protein p-glycoprotein, which associates with resistance to corticosteroids and other immunosuppressive drugs. This narrative review overviews the evidence regarding Th17.1 lymphocytes in different inflammatory rheumatic diseases. It is now recognized that Th17.1 lymphocytes are increased in the synovial fluid of affected joints in rheumatoid arthritis (RA) and associate with poor treatment response to abatacept. Th17.1 lymphocytes from synovial fluid of RA are less responsive to immunosuppression than those from the peripheral blood. In sarcoidosis, Th17.1 lymphocytes are concentrated in mediastinal lymph nodes and alveolar lining. Such Th17.1 lymphocytes in sarcoidosis are the predominant source of IFN-γ in the sarcoid lung. Th17.1 lymphocytes are elevated in lupus and Takayasu arteritis and associate with disease activity. Future studies should evaluate isolated Th17.1 lymphocytes from peripheral blood or sites of pathology such as synovial fluid and assess their modulation with immunosuppressive therapy in vitro. The analysis of gene expression signature of isolated Th17.1 lymphocytes might enable the identification of newer therapeutic strategies specifically targeting these cell populations in inflammatory rheumatic diseases. Key Points • Th17.1 lymphocytes are a subset of Th17 lymphocytes secreting both IFN-γ and IL-17 • Th17.1 lymphocytes drive neutrophilic inflammation, granuloma formation, and corticosteroid resistance • Th17.1 lymphocytes are elevated in rheumatoid arthritis and sarcoidosis at sites of inflammation • Increased circulating Th17.1 lymphocytes have been identified in lupus and Takayasu arteritis and associate with active disease.

Toward Overcoming Treatment Failure in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disorder characterized by inflammation and bone erosion. The exact mechanism of RA is still unknown, but various immune cytokines, signaling pathways and effector cells are involved. Disease-modifying antirheumatic drugs (DMARDs) are commonly used in RA treatment and classified into different categories. Nevertheless, RA treatment is based on a "trial-and-error" approach, and a substantial proportion of patients show failed therapy for each DMARD. Over the past decades, great efforts have been made to overcome treatment failure, including identification of biomarkers, exploration of the reasons for loss of efficacy, development of sequential or combinational DMARDs strategies and approval of new DMARDs. Here, we summarize these efforts, which would provide valuable insights for accurate RA clinical medication. While gratifying, researchers realize that these efforts are still far from enough to recommend specific DMARDs for individual patients. Precision medicine is an emerging medical model that proposes a highly individualized and tailored approach for disease management. In this review, we also discuss the potential of precision medicine for overcoming RA treatment failure, with the introduction of various cutting-edge technologies and big data.

Clinical relevance of P-glycoprotein activity on peripheral blood mononuclear cells and polymorphonuclear neutrophils to methotrexate in systemic lupus erythematosus patients

To elucidate the relationship between P-glycoprotein activity on peripheral blood leukocytes of systemic lupus erythematosus (SLE) patients with lupus arthritis and the clinical response to methotrexate. An observational study was made in patients with SLE according to ACR criteria 1997 who had arthralgia and arthritis and received methotrexate for ≥3 months. Methotrexate responders and non-responders were compared according to the Clinical Disease Activity Index. Mononuclear cells and polymorphonuclear neutrophils were isolated from SLE patients and P-glycoprotein expression was measured using the relative fluorescence index and percentage of positive cells. The chi-square test was used to compare P-glycoprotein activity between responders and non-responders. Thirty-two patients with a mean age of 45.4 ± 10.7 years were included: 34.4% had a response to methotrexate and 65.6% did not. Mean relative fluorescence units of both mononuclear cells and polymorphonuclear neutrophils were significantly lower in patients with a good response (7.0 ± 4.3 vs. 9.6 ± 3.8; p = 0.041 and 4.2 ± 3.5 vs. 7.6 ± 4.0; p = 0.004). The prevalence of low fluorescence levels (<6 relative fluorescence units), signifying higher P-glycoprotein activity of both mononuclear cells and polymorphonuclear neutrophils, was higher in methotrexate responders than in non-responders (27.3 vs. 4.8%; p = 0.10 and 81.8 vs. 23.8%; p = 0.003, respectively). In SLE patients with joint involvement treated with methotrexate, P-glycoprotein activity was higher in responders to methotrexate than in non-responders. Further studies are required to determine the mechanisms behind this finding and whether P-glycoprotein activity mediates alterations in methotrexate efficacy.

Genotype and haplotype analysis of ABCB1 at 1236, 2677 and 3435 among systemic sclerosis patients

Systemic sclerosis (SSc) belongs to the group of systemic diseases of the connective tissue, which are characterized by a chronic autoimmune inflammatory process. P-glycoprotein, initially associated with the drug resistance in patients with cancer, becomes more and more often a subject of considerations in terms of its significance in the development of illnesses, including autoimmune diseases. The aim of the study was an attempt to answer the question whether there was a relationship between ABCB1 polymorphisms and morbidity of systemic sclerosis in a Polish population. The study was carried out in 61 patients with SSc and 100 healthy volunteers. Determination of polymorphisms C1236T and C3435T in ABCB1 was carried out with the PCR-RFLP (polymerase chain reaction - restriction fragment length polymorphism) method. The G2677T/A ABCB1 polymorphism was analysed with the allele-specific PCR method. No statistically significant differences were observed in the frequencies of ABCB1 genotypes and alleles between SSc patients and the control group. It was observed that haplotype 1236 C-2677 G-3435 T occurred in the group of patients with SSc statistically more frequently than in the group of healthy volunteers (25% vs. 15%; p = .032). Carriers of the haplotype demonstrated almost a twofold greater risk of SSc (OR = 1.85; p = .032). No statistically significant correlations for the other nine haplotypes were found. Presented results concerning the relationship of ABCB1 polymorphisms with susceptibility to systemic sclerosis are the first ones that were obtained in a Polish population. They imply that single nucleotide polymorphisms do not affect the risk for SSc, but the 1236 C-2677 G-3435 T haplotype might increase this risk.

ABCB1 gene is associated with the risk of bullous pemphigoid in a polish population

BACKGROUND AND OBJECTIVES

Polymorphisms in the P-glycoprotein-encoding ABCB1 gene may affect the intracellular concentration of xenobiotics, and thus contribute to the development of autoimmune diseases, including bullous pemphigoid (BP). The objective of the present study was to investigate whether there is an association between the C3435T and G2677T/A polymorphisms in the ABCB1 gene and the risk of BP in a Polish population.

PATIENTS AND METHODS

The study included 71 patients with BP and 156 healthy volunteers. Determination of the C3435T polymorphism was carried out using PCR-RFLP; the G2677T/A polymorphism, using allele-specific PCR.

RESULTS

While there was no correlation between the C3435T polymorphism and the risk of BP, we did find such an association with respect to the G2677T/A polymorphism. The relative risk of BP was more than five times greater in individuals with the 2677TA genotype (OR = 5.52, p = 0.0063), and more than twice as high in carriers of the 2677TT genotype (OR = 2.40, p = 0.0076). At 2.40 (0.000018), the OR in carriers of the 2677T allele was also increased. The greater prevalence of the 2677GG genotype and the 2677G allele in the control group, as well as the OR < 1.0 (0.22 and 0.33, respectively), suggest a protective role of the 2677G allele with respect to the development of BP.

CONCLUSIONS

The results of the present study indicate that the G2677T/A polymorphism in the ABCB1 gene may affect the risk of developing BP.

Genetic variation in the glucocorticoid pathway involved in interindividual differences in the glucocorticoid treatment

Glucocorticoids (GCs) are widely used for treating asthma, rheumatoid arthritis, nephrotic syndrome, acute lymphoblastic leukemia and other autoimmune diseases. However, in a subgroup of patients, failure to respond to GCs is known as GC resistance or GC insensitivity. This represents an important barrier to effective treatment and a clinical problem requiring an urgent solution. Genetic variation in the GC pathway is a significant factor in interindividual differences in GC treatment. This article reviews the pharmacogenetics of GCs in diverse diseases based on the GC pathway.

MDR-1 and MRP-1 activity in peripheral blood leukocytes of rheumatoid arthritis patients

Background

Rheumatoid Arthritis is a chronic disease leading to decreased quality of life with a rather variable response rate to Disease Modifying Anti Rheumatic Drugs. Methotrexate (MTX) is the gold standard therapy in Rheumatoid Arthritis. The Multidrug resistance Related Protein and Multi Drug Resistance protein 1, also called P-glycoprotein-170 transporters can alter the intracellular concentration of different drugs. Methotrexate is an MRP1 substrate and thus the functional activity of MRP1 might have a clinical impact on the efficiency of the Methotrexate-therapy in Rheumatoid Arthritis.

Methods

We have compared the functional Multidrug Activity Factors (MAF) of the MDR1 and MRP1 transporters of Peripheral Blood Leukocytes of 59 Rheumatoid Arthritis patients with various response rate to MTX-therapy (MTX-responder, MTX-resistant and MTX-intolerant RA-groups) and 47 non-RA controls in six different leukocyte subpopulations (neutrophil leukocytes, monocytes, lymphocytes, CD4+, CD8+ and CD19+ cells). There was a decreased MAF of RA patients compared to non- Rheumatoid Arthritis patients and healthy controls in the leukocyte subpopulations. There was a significant difference between the MAF values of the MTX-responder and MTX intolerant groups. But we have not found significant differences between the MAF values of the MTX-responder and MTX-resistant Rheumatoid Arthritis -groups.

Results

Our results suggest that MDR1 and MRP1 functional activity does not seem to affect the response rate to MTX-therapy of Rheumatoid Arthritis-patients, but it might be useful in predicting MTX-side effects. We have demonstrated the decreased functional MDR-activity on almost 60 Rheumatoid Arthritis patients, which can be interpreted as a sign of the immune-suppressive effect of the MTX-treatment.

Multidrug resistance protein-1 expression, function and polymorphisms in patients with rheumatoid arthritis not responding to methotrexate

OBJECTIVE

To study the expression, function and polymorphism of MDR-1 protein on the peripheral blood lymphocytes in patients with RA following treatment with MTX and its relationship with response to therapy.

METHODS

RA patients naïve to MTX/DMARD- and glucocorticoid were enrolled. Expression and function of MDR-1 was carried out by flow cytometry at baseline and after 4 months of therapy. MDR-1 expression was measured by relative fluorescence intensities and percentage of positive cells. MDR-1 function was assessed by Rhodamine efflux in presence or absence of verapamil. Patients with reduction in disease activity score 28 ≥1.2 were defined as responders and <1.2 as non-responders. Three single nucleotide polymorphisms in MDR-1 gene, 3435T, 1236T and 2677T/A were studied.

RESULTS

Fifty-two patients of RA were grouped into responders (n = 41), and non-responders (n = 11) as per the defined criteria. There was no difference between the groups in terms of age, sex ratio or duration of illness, MTX dose and follow-up duration. The expression and function of the MDR-1 protein reduced significantly in the responder group after the treatment with MTX when compared to the baseline evaluation. The decrease was significant when compared to the non-responders at the fourth month. MDR-1 expression and function either increased or remained the same in the non-responder group after treatment with MTX. MTX unresponsiveness was not related to any of the three polymorphisms studied.

CONCLUSION

Persistent expression and function of MDR-1 identifies a subset of RA patients not responding to MTX. Its early recognition may help in appropriately modulating therapy.

P-glycoprotein and drug resistance in systemic autoimmune diseases

Autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and psoriatic arthritis (PsA) are chronic inflammatory disorders of unknown etiology characterized by a wide range of abnormalities of the immune system that may compromise the function of several organs, such as kidney, heart, joints, brain and skin. Corticosteroids (CCS), synthetic and biologic immunosuppressive agents have demonstrated the capacity to improve the course of autoimmune diseases. However, a significant number of patients do not respond or develop resistance to these therapies over time. P-glycoprotein (P-gp) is a transmembrane protein that pumps several drugs out of the cell, including CCS and immunosuppressants; thus, its over-expression or hyper-function has been proposed as a possible mechanism of drug resistance in patients with autoimmune disorders. Recently, different authors have demonstrated that P-gp inhibitors, such as cyclosporine A (CsA) and its analogue Tacrolimus, are able to reduce P-gp expression and or function in SLE, RA and PsA patients. These observations suggest that P-gp antagonists could be adopted to revert drug resistance and improve disease outcome. The complex inter-relationship among drug resistance, P-gp expression and autoimmunity still remains elusive.

Glucocorticoid sensitivity in health and disease

Glucocorticoids regulate many physiological processes and have an essential role in the systemic response to stress. For example, gene transcription is modulated by the glucocorticoid-glucocorticoid receptor complex via several mechanisms. The ultimate biologic responses to glucocorticoids are determined by not only the concentration of glucocorticoids but also the differences between individuals in glucocorticoid sensitivity, which is influenced by multiple factors. Differences in sensitivity to glucocorticoids in healthy individuals are partly genetically determined by functional polymorphisms of the gene that encodes the glucocorticoid receptor. Hereditary syndromes have also been identified that are associated with increased and decreased sensitivity to glucocorticoids. As a result of their anti-inflammatory properties, glucocorticoids are widely used in the treatment of allergic, inflammatory and haematological disorders. The variety in clinical responses to treatment with glucocorticoids reflects the considerable variation in glucocorticoid sensitivity between individuals. In immune-mediated disorders, proinflammatory cytokines can induce localized resistance to glucocorticoids via several mechanisms. Individual differences in how tissues respond to glucocorticoids might also be involved in the predisposition for and pathogenesis of the metabolic syndrome and mood disorders. In this Review, we summarize the mechanisms that influence glucocorticoid sensitivity in health and disease and discuss possible strategies to modulate glucocorticoid responsiveness.

MDR1a/1b gene silencing enhances drug sensitivity in rat fibroblast-like synoviocytes

BACKGROUND

Drug resistance mediated by P-glycoprotein (P-gp) is one of the major reasons for the failure of rheumatoid arthritis (RA) therapy with disease modifying anti-rheumatic drugs and glucocorticoids. In the present study, we aimed to investigate the in vitro effectiveness of small interfering RNA (siRNA) to render rat fibroblast-like synoviocytes (FLS) susceptible to drugs. We also attempted the electroporation-mediated transfer of siRNA against multidrug resistance (MDR) genes into rat knee joints.

METHODS

FLS were transfected with siRNAs corresponding to MDR1a and MDR1b genes. FLS were treated with dexamethasone (DEX) and lipopolysaccharide. The mRNA and protein levels of tumor necrosis factor-alpha, interleukin (IL)-6 and IL-1beta were measured. Both siRNAs were co-transduced into rat knee joints by an electroporation method and evaluated the target gene expressions in the synovium.

RESULTS

Each siRNA could sequence-specifically reduce the target gene expression by over 70% and effectively suppressed P-gp expression and function in the FLS. Both gene expression and protein production of the inflammatory cytokines in the cells transfected with siRNA were reduced by a greater amount compared to in control cells. The in vivo electroporation-mediated transduction of siRNA could significantly inhibit the target gene expressions.

CONCLUSIONS

MDR1a/1b gene silencing by siRNA could effectively inhibit P-gp in rat FLS, resulting in a significant enhancement of the anti-inflammatory effects of DEX. The in vivo siRNA transduction could successfully silence MDR gene expression in the rat synovium. These findings indicate that the siRNA targeting MDR gene could be a useful tool for treating refractory arthritis in RA.

Prediction of response to disease modifying antirheumatic drugs in rheumatoid arthritis

AIM

To investigate potential predictors of response to conventional DMARDs in RA.

METHODS

Study design - 6-month follow-up prospective study.

PARTICIPANTS

RA patients with active disease. INTERVENTION AND FOLLOW-UP: Introduction of one DMARD. Response to treatment evaluated at 6 months (ACR20 criteria).

ANALYSIS

Potential predictors of response, patients' demographics, disease activity, percentages of PBMC subsets expressing P-gp, serum IL-1β, IL-6, IL-8, IL-10, IL-12, TNF-α levels, were evaluated using univariate and multivariate logistic regression analysis. ROC curve analyses were performed in order to obtain thresholds allowing the prediction of response.

RESULTS

Forty-two patients (mean age = 57 ± 13 years, mean disease duration = 5.4 ± 7.2 years) were included. MTX was given to 30. The response to therapy was predicted by the baseline serum level of TNF-α (mean = 30.2 pg/ml ± 18 in non-responders vs. 11.9 pg/ml ± 11.2 in responders). The threshold, which predicted with the best accuracy the response to treatment, was 20.1 pg/ml (sensitivity, specificity, positive and negative predictive values of 75, 78.9, 83.3, and 69.2%, respectively; AUC = 80.3%, 95% CI = 62.8-97.7%). Similar results were obtained in the subgroups of patients treated with MTX and patients with early RA of less than 3 years duration.

CONCLUSION

In the present work, the serum concentration of TNF-α was related to further response to DMARDs. Other works are needed for confirmation and to assess whether such biomarker could be used to predict the response to DMARDs at the individual level.

Etanercept overcomes P-glycoprotein-induced drug resistance in lymphocytes of patients with intractable rheumatoid arthritis

P-glycoprotein (P-gp) on activated lymphocytes is an adenosine triphosphate (ATP)-binding cassette transporter that causes drug resistance by exclusion of intracellular drugs in patients with active rheumatoid arthritis (RA). However, infliximab with methotrexate (MTX) can overcome P-gp-mediated drug resistance. We encounter patients who cannot continue infliximab or MTX. Here we tested how etanercept affected P-gp-mediated drug resistance in such intractable RA patients. Peripheral lymphocytes of 11 RA patients (3 switched from infliximab and 8 who could not be treated with MTX) were analyzed for P-gp expression by flow cytometry and for drug exclusion using radioisotope-labeled dexamethasone. Activated lymphocytes of RA patients overexpressed P-gp and coexpressed CD69. Incubation of these lymphocytes with dexamethasone in vitro reduced intracellular dexamethasone levels. Two-week etanercept therapy significantly reduced P-gp expression and eliminated such P-gp- and CD69-high-expressing subgroup. The reduction in P-gp resulted in recovery of intracellular dexamethasone levels in lymphocytes and improvement of disease activity, thus allowing tapering of corticosteroids. None of the patients experienced any severe adverse effects. Etanercept is useful for overcoming P-gp-mediated treatment resistance in intractable RA patients who have to discontinue infliximab or are intolerant to MTX.

ABC drug transporters and immunity: novel therapeutic targets in autoimmunity and cancer

ABC transporters were identified originally for their contribution to clinical MDR as a result of their capacity to extrude various unrelated cytotoxic drugs. More recent reports have shown that ABC transporters can play important roles in the development, differentiation, and maturation of immune cells and are involved in migration of immune effector cells to sites of inflammation. Many of the currently identified, endogenous ABC transporter substrates have immunostimulating effects. Increasing the expression of ABC transporters on immune cells and thereby enhancing immune cell development or functionality may be beneficial to immunotherapy in the field of oncology. On the contrary, in the treatment of autoimmune diseases, blockade of these transporters may prove beneficial, as it could dampen disease activity by compromising immune effector cell functions. This review will focus on the expression, regulation, and substrate specificity of ABC transporters in relation to functional activities of immune effector cells and discusses implications for the treatment of cancer on the one hand and autoimmune diseases on the other.

Modulation of Oral Drug Bioavailability: From Preclinical Mechanism to Therapeutic Application

Currently, more than one fourth of all anticancer drugs are developed as oral formulations, and it is expected that this number will increase substantially in the near future. To enable oral drug therapy, adequate oral bioavailability must be achieved. Factors that have proved to be important in limiting the oral bioavailability are the presence of ATP-binding cassette drug transporters (ABC transporters) and the cytochrome P450 enzymes. We discuss the tissues distribution and physiological function of the ABC transporters in the human body, their expression in tumors, currently known polymorphisms and drugs that are able to inhibit their function as transporter. Furthermore, the role of the ABC transporters and drug-metabolizing enzymes as mechanisms to modulate the pharmacokinetics of anticancer agents, will be reviewed. Finally, some clinical examples of oral drug modulation are discussed. Among these examples are the coadministration of paclitaxel with CsA, a CYP3A4 substrate with P-glycoprotein (P-gp) modulating activity, and topotecan combined with the BCRP/P-gp transport inhibitor elacridar. Both are good examples of improvement of oral drug bioavailability by temporary inhibition of drug transporters in the gut epithelium.

Neuroendocrine-immune interactions in rheumatoid arthritis: mechanisms of glucocorticoid resistance

Rheumatoid arthritis (RA) is characterized by chronic inflammation of the synovial membrane, leading to joint destruction. Many autoimmune diseases and disease states of chronic inflammation are accompanied by alterations in the complex interactions between the endocrine, nervous and immune systems. Glucocorticoids, an end product of the hypothalamic-pituitary-adrenal axis, are a mainstay treatment for many autoimmune diseases, including RA, because of their potent anti-inflammatory action. However, about 30% of patients with RA fail to respond to steroid therapy. There are various mechanisms that may contribute to the development of glucocorticoid resistance in inflammatory disorders, which will be the subject of this review. In addition, glucocorticoid resistance may be a contributing factor in the development of inflammatory/autoimmune diseases themselves. Therefore, further elucidation of these mechanisms will reveal new targets for therapeutic intervention in the treatment of RA.

Is steroid resistance related to multidrug resistance-I (MDR-I) in rheumatoid arthritis?

Both healthy ageing and rheumatoid arthritis (RA) are frequently associated with acquired steroid resistance. Here, we investigated the potential involvement of steroid resistance with multidrug resistance (MDR) and explored the impact of pathological ageing on lymphocyte sensitivity to glucocorticoids. Seventy-four RA patients and 26 healthy controls took part in this study. Peripheral blood mononuclear cells were isolated and T-cell sensitivity to glucocorticoids was measured in vitro. The functional activity of P-glycoprotein was analyzed by flow cytometry and ABCB1/MDR-1 gene polymorphisms were assessed in peripheral lymphocytes. Patients and controls had similar sensitivities to glucocorticoids. Only controls presented age-related immunological changes, including reduced T-cell proliferation and relative resistance to corticosterone. Patients had a higher percentage (72%) of lymphocytes actively extruding rhodamine 123 (Rh123(dim)) than controls (60%) in spite of similar P-glycoprotein activity. A higher percentage of Rh123(dim)+ lymphocytes was observed in patients who were more resistant to dexamethasone in vitro. The distribution of ABCB1 genotypes in RA patients did not differ significantly from that in controls and were not associated to steroid sensitiveness or disease activity. These data suggest that peripheral lymphocytes of arthritic patients are fully responsive to GCs in vitro in spite of displaying higher MDR activity.

Drug Insight: resistance to methotrexate and other disease-modifying antirheumatic drugs--from bench to bedside

The chronic nature of rheumatoid arthritis (RA) means that patients require drug therapy for many years. Many RA patients, however, have to discontinue treatment because of drug-related toxic effects, loss of efficacy, or both. The underlying molecular cause for loss of efficacy of antirheumatic drugs is not fully understood, but it might be mediated, at least in part, by mechanisms shared with resistance to anticancer drugs. This Review outlines molecular mechanisms that could be involved in the onset of resistance to, or the loss of efficacy of, disease-modifying antirheumatic drugs in RA patients, including methotrexate, sulfasalazine, chloroquine, hydroxychloroquine, azathioprine, and leflunomide. The mechanisms suggested are based on findings from experimental laboratory studies of specific drug-uptake and drug-efflux transporters belonging to the superfamily of multidrug-resistance transporters, alterations in intracellular drug metabolism, and genetic polymorphisms of drug transporters and metabolic enzymes. We also discuss strategies to overcome resistance and the current clinical studies aiming to predict response and risk of toxic effects. More in-depth knowledge of the mechanisms behind these features could help facilitate a more efficient use of disease-modifying antirheumatic drugs.

Fragmented hyaluronan induces transcriptional up-regulation of the multidrug resistance-1 gene in CD4+ T cells

P-glycoprotein, encoded by the multidrug resistance (MDR)-1 gene, expels various drugs from cells resulting in multidrug resistance. We found previously that interleukin-2, a lymphocyte-activation cytokine, induces P-glycoprotein expression on lymphocytes. Lymphocyte activation involves adhesion with the extracellular matrix, such as hyaluronan, through adhesion molecules on lymphocytes. We investigated the transcriptional regulation of MDR-1 in lymphocytes by fragmented hyaluronan. Fragmented hyaluronan (especially the 6.9-kDa form), not native high molecular hyaluronan, induced translocation of YB-1, a specific transcriptional factor for MDR-1, from the cytoplasm into the nucleus and resulted in the transcription of MDR-1 and the expression of P-glycoprotein on lymphocytes in a dose-dependent manner. Transfection of YB-1 antisense oligonucleotides inhibited P-glycoprotein expression induced by fragmented hyaluronan. The fragmented hyaluronan induced significant P-glycoprotein expression on only activated CD4+ T cells, which highly expressed CD69, and resulted in excretion of intracellular dexamethasone added in vitro. Cyclosporin A, a competitive P-glycoprotein inhibitor, restored intracellular dexamethasone levels in CD4+ T cells. Anti-CD44 monoclonal antibody (Hermes-1) inhibited fragmented hyaluronan-induced YB-1 activation and P-glycoprotein expression in CD4+ T cells. We provide the first evidence that binding of fragmented hyaluronan to CD44 induces YB-1 activation followed by P-glycoprotein expression in accordance with activation of CD4+ T cells. Our findings imply that CD4+ T cell activation by fragmented hyaluronan, induced by characteristic extracellular matrix changes in inflammation, tumors, and other conditions, results in P-glycoprotein-mediated multidrug resistance.

The effect of 3435C>T MDR1 gene polymorphism on rheumatoid arthritis treatment with disease-modifying antirheumatic drugs

OBJECTIVE

Rheumatoid arthritis (RA) is a multifactorial disease, with immunological, genetical as well as environmental factors being implicated in its pathogenesis. Treatment of RA is based mainly on drugs modulating the course of the disease, e.g. methotrexate (MTX) or sulfasalazine (SL). The MDR1 gene product, P-glycoprotein (P-gp), is probably one of the most important and best defined transporters for drug delivery in humans. P-gp transports a wide range of substrates with diverse chemical structures, among them anticancer agents, cardiac drugs, and immunosuppressants. The aim of this study was to examine the effect of the 3435C>T MDR1 gene polymorphism on the efficacy of RA treatment with disease-modifying antirheumatic drugs, i.e. MTX plus methylprednisolone (MP), and SL.

METHODS

The study was carried out on 255 patients with RA treated according to two regimes: (1) MTX (7.5-15.0 mg weekly) plus low doses of MP (n=174), (2) SL (1.5-3 g daily, n=81).

RESULTS

The probability of remission of RA symptoms after MTX plus MP therapy was 4.65-fold higher in carriers of the TT genotype compared to patients with CC genotype (P=0.003, OR 4.65, 95%CI 1.66-13.05), whereas the probability of remission of RA symptoms in patients treated with SL was 2-fold higher in carriers of TT genotype compared to patients with CC genotype, but did not reach statistical significance (P=0.358, OR=2.00 95% CI=0.58-6.87).

CONCLUSION

The results from the present study suggest that the 3435C>T MDR1 gene polymorphism may influence the efficacy of RA therapy with disease-modifying antirheumatic drugs.

Down regulation of multidrug resistance protein-1 expression in patients with early rheumatoid arthritis exposed to methotrexate as a first disease-modifying antirheumatic drug

BACKGROUND

Methotrexate (MTX) is the current gold standard conventional disease-modifying antirheumatic drug (DMARD) and is effluxed from cells by several transmembrane proteins, including multidrug resistance protein-1 (MRP1). It is hypothesised that the overexpression of these proteins may mediate reduced efficacy of MTX. To date, it is unclear how expression of these proteins changes over time or after exposure to drugs.

AIMS

To compare MRP1 expression in newly diagnosed patients with DMARD-naive rheumatoid arthritis with that in healthy controls and to investigate how MRP1 expression changed after exposure to MTX.

METHODS

18 newly diagnosed patients with DMARD-naive rheumatoid arthritis and 14 healthy controls were recruited. Peripheral blood mononuclear cell counts were taken at baseline and after 6 months' treatment with MTX. Cells were separated by density gradient centrifugation and MRP1 expression was measured using the QCRL-1 monoclonal antibody.

RESULTS

MRP1 expression in patients did not seem to be up regulated compared with that in healthy controls. In patients who were positive for MRP1 at baseline (61%), treatment with MTX and folic acid led to a marked down regulation of MRP1 expression at 6 months.

CONCLUSION

In patients with rheumatoid arthritis expressing MRP1, treatment with MTX and folic acid led to down regulation of MRP1 expression. Further studies are required to determine the mechanism behind this observation and whether MRP1 expression mediates altered efficacy to MTX.

Acquired resistance to chloroquine in human CEM T cells is mediated by multidrug resistance–associated protein 1 and provokes high levels of cross-resistance to glucocorticoids

OBJECTIVE

To explore the onset and molecular mechanism of resistance to the antimalarial disease-modifying antirheumatic drug (DMARD) chloroquine (CQ) in human CEM T cells.

METHODS

Human CEM cells were used as an in vitro model system to study the development of CQ resistance by growing cells in stepwise increasing concentrations of CQ.

RESULTS

Over a period of 6 months, CEM cell lines developed 4-5-fold resistance to CQ. CQ resistance was associated with the specific overexpression of multidrug resistance-associated protein 1 (MRP-1), an ATP-driven drug efflux pump. This was illustrated by 1) overexpression of MRP-1 by Western blotting and 2) the complete reversal of CQ resistance by the MRP-1 transport inhibitors MK571 and probenecid. Importantly, CQ-resistant CEM cells retained full sensitivity to other DMARDs, including methotrexate, leflunomide, cyclosporin A, and sulfasalazine, but exhibited a high level of cross-resistance (>1,000-fold) to the glucocorticoid dexamethasone. The mechanistic basis for the latter was associated with aberrant signaling via the cAMP-protein kinase A pathway, since the cAMP-inducing agent forskolin reversed dexamethasone resistance. Finally, CQ-resistant CEM cells displayed a markedly reduced capacity to release proinflammatory cytokines (tumor necrosis factor alpha) and chemokines (interleukin-8).

CONCLUSION

Induction of overexpression of the multidrug resistance efflux transporter MRP-1 can emerge after long-term exposure to CQ and results in CQ resistance and collateral resistance to dexamethasone. These findings warrant further detailed investigations into the possible role of MRP-1 and other members of the superfamily of drug efflux pumps in diminishing the efficacy of DMARDs in rheumatoid arthritis treatment.

P-glycoprotein in autoimmune diseases

Multidrug resistance-1 (MDR-1) is characterized by overfunction of P-glycoprotein (P-gp), a pump molecule that decreases intracellular drug concentration by effluxing them from the intracellular space. Broad ranges of structurally unrelated compounds are transported by P-gp, including antineoplastic agents, HIV protease inhibitors, prednisone, gold salts, methotrexate, colchicine as well as several antibiotics. In contrast, many other compounds such as calcium channel blockers (verapamil) and immunosupressors (cyclosporine-A) are able to inhibit P-gp function. The P-gp role in therapeutic failures has been extensively studied in cancer; however, there is little information regarding MDR-1 phenotype in autoimmune disorders. It has been reported that an increased number of lymphocytes are able to extrude P-gp substrates in rheumatoid arthritis, immune thrombocytopenic purpura and systemic lupus erythematosus, the patients with poor response to treatment being the ones that exhibit the highest values. This may be due, at least in part, to a simultaneous long-term usage of several drugs that induce P-gp function. Since abnormally activated cell compartments characterize autoimmune diseases, it is possible that those cells are the ones that exhibit drug resistance. The study of drug resistance mechanisms in autoimmunity may be helpful for the optimization of the current therapeutic schemes through their combination with low doses of P-gp inhibitors.

Expression of resistance markers to methotrexate predicts clinical improvement in patients with rheumatoid arthritis

BACKGROUND

Methotrexate is transported into the cell by the reduced folate carrier (RFC) and out of the cell by members of the multidrug resistance protein family (MRP). Transport proteins may affect the therapeutic efficacy of this drug in patients with rheumatoid arthritis.

OBJECTIVE

To investigate the potential benefit of the presence of RFC and the absence of functional MRP for the efficacy of methotrexate treatment.

METHODS

The study involved 163 patients (116 female, 47 male; mean age 59.5 years) on methotrexate (mean weekly dose 12.2 mg). RFC was determined using reverse transcriptase polymerase chain reaction, and MRP function by flow cytometry, using a calcein acetoxymethylesther/probenecid assay. Clinical response to methotrexate was evaluated by the EULAR response criteria and the ACR 20% improvement criteria. The clinical data were obtained at the beginning of methotrexate treatment and at the time of blood sampling during ongoing therapy. Patients were divided into four groups according to the presence (+) or absence (-) of RFC and functional (f) MRP.

RESULTS

fMRP+/RFC+ and fMRP-/RFC- patients more often had good EULAR response rates (60%, p = 0.014, and 53%, p = 0.035, respectively) in comparison with the fMRP-/RFC+ group (29%); fMRP+/RFC- patients had a low frequency of good disease activity responses.

CONCLUSIONS

Absence of fMRP plus presence of RFC did not prove to be related to beneficial effects of methotrexate, but the lack or the presence of both fMRP and RFC led to a significantly better therapeutic outcome. Determination of these markers may predict responsiveness to methotrexate.

Acquired resistance of human T cells to sulfasalazine: stability of the resistant phenotype and sensitivity to non-related DMARDs

BACKGROUND

A recent study from our laboratory showed that induction of the multidrug resistance related drug efflux pump ABCG2 contributed to acquired resistance of human T cells to the disease modifying antirheumatic drug (DMARD) sulfasalazine (SSZ).

OBJECTIVES

To investigate the duration of SSZ resistance and ABCG2 expression after withdrawal of SSZ and rechallenging with SSZ, and to assess the impact of SSZ resistance on responsiveness to other DMARDs.

METHODS

Human CEM cells (T cell origin) with acquired resistance to SSZ (CEM/SSZ) were characterised for (a) SSZ sensitivity and ABCG2 expression during withdrawal and rechallenge of SSZ, and (b) antiproliferative efficacy of other DMARDs.

RESULTS

ABCG2 protein expression was stable for at least 4 weeks when CEM/SSZ cells were grown in the absence of SSZ, but gradually declined, along with SSZ resistance levels, to non-detectable levels after withdrawal of SSZ for 6 months. Rechallenging with SSZ led to a rapid (<2.5 weeks) resumption of SSZ resistance and ABCG2 expression as in the original CEM/SSZ cells. CEM/SSZ cells displayed diminished sensitivity to the DMARDs leflunomide (5.1-fold) and methotrexate (1.8-fold), were moderately more sensitive (1.6-2.0 fold) to cyclosporin A and chloroquine, and markedly more sensitive (13-fold) to the glucocorticoid dexamethasone as compared with parental CEM cells.

CONCLUSION

The drug efflux pump ABCG2 has a major role in conferring resistance to SSZ. The collateral sensitivity of SSZ resistant cells for some other (non-related) DMARDs may provide a further rationale for sequential mono- or combination therapies with distinct DMARDs upon decreased efficacy of SSZ.

Contribution of patient related differences to multidrug resistance in rheumatoid arthritis

BACKGROUND

There is a wide variation in responses to standard disease modifying antirheumatic drug (DMARD) treatment in rheumatoid arthritis (RA). Whether multidrug resistance, failure to respond to several DMARDs, is a specific entity over and above that expected by chance alone is unclear.

OBJECTIVE

To identify patients with RA who demonstrate a multidrug resistant phenotype and to determine what proportion of the variance in drug responses is due to patient related factors.

METHODS

Patients with RA (1987 American College of Rheumatology criteria) were identified from clinics at Manchester Royal Infirmary and through the Arthritis Research Campaign National RA Repository. The clinic records were reviewed and multidrug resistance was defined as stopping three or more DMARDs owing to lack of efficacy after an adequate trial of the drug. Logistic regression measured by a random effects model was used to determine the relative contribution of the drug and subject related differences to the multidrug resistance.

RESULTS

265 patients (210 (79.3%) female) were studied. The mean (SD) age and disease duration were 52.2 (12.9) and 10.7 (8.8) years, respectively. Patients had a median (range) of 2 (1-8) DMARD courses. Failure of at least one DMARD due to inefficacy occurred in 105 (40%) and 13 (5%) were multidrug resistant. Overall, 35% of the variance in drug responses was due to between-subject differences (p=0.02). Rheumatoid factor (RF) status contributed significantly to this (OR=2.15, 95% confidence interval (95% CI) 1.00 to 4.62) but explained only 3% of the total variance in drug inefficacy.

CONCLUSION

Multidrug resistance occurs in an uncommon (5%) but important subgroup of patients with RA. The between-subject variance is not fully explained by demographics and RF status. Understanding the biological mechanisms that contribute to multidrug resistance may suggest new therapeutic approaches and targets in RA.

Therapeutic relevance of altered cytokine expression

Cytokines and their receptors have numerous physiological functions. Altered concentrations of these mediators are associated with various afflictions. For example, over-expression of cytokines has been associated with altered drug concentrations and activity. Greater concentrations of cardiovascular drugs have been observed in humans and laboratory animals with various types of inflammatory disorders compared to healthy controls. Interestingly, the observed higher concentrations of drugs such as propranolol and verapamil have not been associated with increased effects. Indeed, reduced response to these cardiovascular drugs is observed, suggestive of cytokine-mediated downregulation of receptors. Increased cytokine concentrations have also been associated with decreased response to drugs used in treatment of other disorders such as AIDS, asthma and psychiatric diseases. This reduced response to drug in the presence of altered cytokine concentrations is especially relevant to the elderly population which has a greater incidence of multiple diseases and elevated concentrations of various cytokines compared to younger individuals. Furthermore, inflammatory conditions and their accompanied increased over-expression of cytokines are suggested to be the main determinants of therapeutic failure in myocardial infarction and angina. Therefore, altered cytokine concentrations may influence therapeutic outcomes of pharmacotherapy and result in treatment failure.