Detection of active P-glycoprotein in systemic lupus erythematosus patients with poor disease control

Serum p-Glycoprotein and Monomeric C-Reactive Protein are Elevated in Takayasu Arteritis

Purpose

Existing biomarkers including C-reactive protein (CRP) do not adequately distinguish active and inactive TAK. We compared serum p-glycoprotein (p-gp)/Multidrug Resistance Protein 1 (MDR1), monomeric CRP (mCRP), CRP, and mCRP:CRP ratio in Takayasu arteritis (TAK) and healthy controls and their relationship with disease activity.

Patients and Methods

Serum p-gp mCRP (ELISA) and CRP (nephelometry) were compared between consecutive adults with TAK (>18 years) enrolled from a prospective cohort (n = 92) and healthy controls (n = 29), and between active vs inactive TAK (n = 46 each). In a subset of active immunosuppressive-naïve TAK (n = 29), correlation was assessed between serum p-gp and p-gp expression on circulating T helper lymphocyte populations: overall (CD4+), Th17 (CD4+IL-17+), Th17.1 (CD4+IL-17+IFN-γ+) lymphocytes [normalized to Tregs (CD4+CD25+FoxP3+)]. Changes in serum p-gp, mCRP, CRP, and mCRP:CRP were compared before and after immunosuppression (n = 29). Data was represented using median (Q1-Q3). Receiver operating characteristics (ROC) curves were generated for TAK vs controls, and active vs inactive TAK with serum p-gp, mCRP, CRP, and mCRP:CRP. Multivariable-adjusted linear regression was used to predict active disease with serum p-gp, mCRP, CRP, or mCRP:CRP.

Results

Serum p-gp (11.19 vs 8.05 ng/mL), mCRP (1.61 vs 1.25 µg/L), and CRP (5.40 vs 2.1 mg/L) were elevated in TAK vs controls (p <0.05 for all). CRP was higher and mCRP:CRP ratio was lower in active vs inactive TAK (p < 0.001). ROC curves identified moderate prediction for active disease with CRP and inactive disease with serum p-gp (area under ROC curve 0.705 and 0.392, respectively). Multivariable-adjusted linear regression confirmed association of CRP with active disease (p = 0.009) and serum p-gp with inactive disease (p = 0.041). In treatment-naïve TAK, serum p-gp negatively correlated with p-gp+Th17.1 lymphocytes (Spearman's rho=-0.39, p = 0.046). CRP and serum p-gp were significantly lowered following immunosuppressive therapy in treatment-naïve TAK (p < 0.05).

Conclusion

Serum p-gp and mCRP are elevated in TAK. Serum p-gp is associated with inactive disease.

A Review of the Potential Benefits of Herbal Medicines, Small Molecules of Natural Sources, and Supplements for Health Promotion in Lupus Conditions

The Latin word lupus, meaning wolf, was in the medical literature prior to the 1200s to describe skin lesions that devour flesh, and the resources available to physicians to help people were limited. The present text reviews the ethnobotanical and pharmacological aspects of medicinal plants and purified molecules from natural sources with efficacy against lupus conditions. Among these molecules are artemisinin and its derivatives, antroquinonol, baicalin, curcumin, emodin, mangiferin, salvianolic acid A, triptolide, the total glycosides of paeony (TGP), and other supplements such as fatty acids and vitamins. In addition, medicinal plants, herbal remedies, mushrooms, and fungi that have been investigated for their effects on different lupus conditions through clinical trials, in vivo, in vitro, or in silico studies are reviewed. A special emphasis was placed on clinical trials, active phytochemicals, and their mechanisms of action. This review can be helpful for researchers in designing new goal-oriented studies. It can also help practitioners gain insight into recent updates on supplements that might help patients suffering from lupus conditions.

Expression pattern of glucocorticoid receptor α gene and associations with clinicolaboratory features in patients with systemic lupus erythematosus

Background

Glucocorticoid receptor α (GRα) gene is a transcription factor with clinically significant immune-modulating properties in various autoimmune diseases. However, the expression pattern of the GRα gene and associations with clinical features in patients with systemic lupus erythematosus (SLE) is controversial. This study aimed to assess the correlation between the GRα expression and different clinical and laboratory-related parameters in SLE patients.

Methods

A total of 45 women with newly diagnosed SLE and 31 gender and age-matched healthy controls were enrolled in this cross-sectional study. The real-time quantitative PCR (qRT-PCT) method evaluated the differences in GRα expression in peripheral blood mononuclear cells from cases and controls. The correlation between the GRα gene expression levels, clinicolaboratory features, and potential prognostic application was also analyzed.

Results

Compared to the healthy individuals, the GRα gene expression in newly diagnosed SLE patients who did not receive any treatment was numerically reduced, but this reduction did not achieve statistical significance (P=0.87). No significant correlation was also found with the activity and severity of SLE according to SLEDAI2K (P=0.41). The GRα gene expression showed a negative correlation with CRP (P=0.034) and a positive correlation with lupus anticoagulant (P=0.039) levels in SLE. The receiver operating characteristic (ROC) curve analysis indicated that the GRα expression level might be a predictor biomarker for low CRP and positive lupus anticoagulant in SLE, respectively.

Conclusion

This study proposed that expression of the GRα in newly diagnosed lupus patients has no statistically significant difference with healthy age and sex-matched controls. Besides, its expression does not correlate with lupus disease activity according to SLEDAI2k. However, further studies in this area are required.

Steroid Resistance Associated with High MIF and P-gp Serum Levels in SLE Patients

Approximately 30% of patients with systemic lupus erythematosus (SLE) present steroid resistance (SR). Macrophage migration inhibition factor (MIF) and P-glycoprotein (P-gp) could be related to SR. This work aims to evaluate the relationship between MIF and P-pg serum levels in SR in SLE. Methods: Case−control study including 188 SLE patients who were divided into two groups (90 in the steroid-resistant group and 98 in the steroid-sensitive (SS) group) and 35 healthy controls. MIF and P-gp serum levels were determined by ELISA. Multivariable logistic regression and chi-squared automatic interaction detection (CHAID) were used to explore risk factors for SR. Results: The steroid-resistant group presented higher MIF and P-gp serum levels in comparison with the SS (p < 0.001) and reference (p < 0.001) groups. MIF correlated positively with P-gp (rho = 0.41, p < 0.001). MIF (≥15.75 ng/mL) and P-gp (≥15.22 ng/mL) were a risk factor for SR (OR = 2.29, OR = 5.27). CHAID identified high P-gp as the main risk factor for SR and high MIF as the second risk factor in those patients with low P-gp. Conclusions: An association between MIF and P-gp serum levels was observed in SR. CHAID identified P-gp ≥ 15.22 ng/mL as the main risk factor for SR. More studies are needed to validate these results.

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.

Research advances in the role and pharmaceuticals of ATP-binding cassette transporters in autoimmune diseases

Autoimmune diseases are caused by the immune response of the body to its antigens, resulting in tissue damage. The pathogenesis of these diseases has not yet been elucidated. Most autoimmune diseases cannot be cured by effective drugs. The treatment strategy is to relieve the symptoms of the disease and balance the body's autoimmune function. The abnormal expression of ATP-binding cassette (ABC) transporters is directly related to the pathogenesis of autoimmune diseases and drug therapy resistance, which poses a great challenge for the drug therapy of autoimmune diseases. Therefore, this paper reviews the interplay between ABC transporters and the pathogenesis of autoimmune diseases to provide research progress and new ideas for the development of drugs in autoimmune diseases.

Molecular mechanisms of glucocorticoid resistance in systemic lupus erythematosus: A review

The treatment of systemic lupus erythematosus (SLE) with glucocorticoids (GCs) is quite effective; however, GC resistance or insensitivity is a major barrier to the treatment of SLE. Therefore, it is necessary to identify the underlying mechanisms that lead to GC resistance. Much evidence shows that the mechanism of GC resistance is very complicated. GC receptor is involved in the main mechanism of GC resistance and was illustrated by a lot of literature. Therefore, this paper focuses on the GC resistance mechanisms of non-glucocorticoids receptor, including P-gp, MIF, TLR9, and Th17 cells. These molecular mechanisms may help diagnose GC resistance and provide an alternative treatment strategy to reverse GC resistance by blocking the underlying mechanisms.

Macrophage activation syndrome at the onset of glucocorticoid-resistant systemic lupus erythematosus: a case report

Introduction. Macrophage activation syndrome (MAS) is a life-threatening hyperinflammatory state mediated by uncontrolled cytokine storm and haemophagocytosis. Although rarely reported, MAS might occur in systemic lupus erythematosus (SLE), notably as an inaugural manifestation. Glucocorticoids (GCs) are the cornerstone of SLE therapy. However, in some cases high doses of GCs are required to achieve remission (i.e. glucocorticoid-resistance), leading to significant side effects.

Case report. A 28-year-old Romani male was admitted to our hospital for polyarthralgia, polyserositis and fatigability. The patient had high-grade fever, jaundice and generalized lymphadenopathy. Laboratory tests revealed severe mixed hemolytic autoimmune anemia, leukopenia, hepatocytolysis, coagulation abnormalities, hypertriglyceridemia, biological inflammatory syndrome, hyperferritinemia and persistent proteinuria of nephritic pattern. Imaging studies showed pleuropericardial effusion, hepatosplenomegaly and polysynovitis. Additional blood tests revealed hypocomplementemia and positive ANA, anti-dsDNA and anti-Sm antibodies. Haemophagocytosis was not identified either on bone marrow or axillary lymph node biopsy specimens. However, SLE-associated MAS seemed to fit this set-up. High-dose corticotherapy (6.5 g methylprednisolone followed by prednisone, 1.5 mg/kg/day after discharge) and intravenous cyclophosphamide were necessary to induce and sustain remission.

Conclusion. MAS is a potentially severe manifestation that should be considered at SLE onset whenever high fever and elevated serum levels of aspartate aminotransferase, lactate dehydrogenase, C-reactive protein, ferritin and procalcitonin are noted. Early diagnosis and prompt treatment lead to remission in two thirds of cases.

Glucocorticoid-resistance leads to the use of high-dose corticotherapy or immunosuppressive agents that could elicit serious side effects. New insights into the molecular mechanisms of glucocorticoid-resistance are needed in order to conceive more adequate GC-therapies.

Drug-induced Rowell syndrome, a rare and difficult to manage disease: A case report

Rowell syndrome is defined as the association between lupus erythematosus, erythema multiforme-like lesions and characteristic immunological changes including positive tests for rheumatoid factor, speckled antinuclear antibody, positive anti-Ro or anti-La antibodies. The present report presents the case of a 45-year-old female patient who was previously diagnosed in January 2010 with terbinafine-induced subacute cutaneous lupus erythematosus and was admitted for a skin eruption consisting of erythematous-papular erythema multiforme-like lesions, primarily on the trunk and limbs. The associated symptoms consisted of fatigability, myalgia and gonalgia. In October 2015, the illness reoccurred ~1 week after the initiation of Helicobacter pylori eradication treatment. Anti-Ro antibodies, rheumatoid factor and antinuclear antibody tests were positive. Given the patient's medical history, clinical manifestations, and laboratory, histopathological and immunofluorescence microscopy findings, a diagnosis of Rowell syndrome was made. Systemic corticosteroids (methylprednisolone; 0.5 mg/kg/day) and immunomodulatory therapy (azathioprine; 50 mg/day) were administered with the associated medication (omeprazole, 20 mg/day; KCl, 1 g/day) and topical dermocorticoids (fluticasone propionate 0.05% cream; 1 application/day), with a favorable outcome. The major diagnostic criteria for Rowell syndrome are the presence of lupus erythematosus (acute, subacute or systemic), erythema multiforme-like lesions and positive testing for antinuclear antibodies. The minor diagnostic criteria for Rowell syndrome are chilblains, the presence of anti-Ro antibodies and positive testing for rheumatoid factor. A diagnosis of Rowell syndrome is made if the patient exhibits all major criteria and at least one minor criterion. The present case met all diagnostic criteria, excluding the presence of chilblains. Notably, in this case there was a co-occurrence of subacute lupus erythematosus and Rowell syndrome lesions, which was drug-induced.

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.

Serum levels of P-glycoprotein and persistence of disease activity despite treatment in patients with systemic lupus erythematosus

Around 25% of patients with systemic lupus erythematosus (SLE) could be refractory to conventional therapies. P-glycoprotein expression on cell surface has been implied on drug resistance, however, to date, it is unknown if P-gp serum levels are associated with SLE disease activity. Evaluate the association of serum P-gp levels and SLE with disease activity despite treatment. A cross-sectional study was conducted on 93 female SLE patients, all receiving glucocorticoids at stable doses for the previous 6 months before to baseline. SLE patients were classified into two groups: (a) patients with active disease [SLE disease activity index (SLEDAI) ≥ 3] despite treatment, and (b) patients with inactive disease (SLEDAI < 3) after treatment. Forty-three healthy females comprised the control group. Serum P-gp, anti-DNA, and both anti-nucleosome antibody levels were measured using ELISA. Active-SLE patients despite treatment had higher P-gp levels compared with inactive-SLE after treatment (78.02 ng/mL ± 114.11 vs. 33.75 ng/mL ± 41.11; p = 0.018) or versus reference group subjects (30.56 ng/mL ± 28.92; p = 0.011). P-gp levels correlated with the scores of SLEDAI (r = 0.26; p = 0.01), Mexican-SLEDAI (MEX-SLEDAI) (r = 0.32; p = 0.002), SLICC/ACR damage index (r = 0.47; p < 0.001), and with prednisone doses (r = 0.33; p = 0.001). In the multivariate model, the high P-gp levels were associated with SLICC/ACR score (p = 0.001), and SLEDAI score (p = 0.014). Our findings support a relationship between serum P-gp levels and SLE with disease activity despite treatment, but it requires further validation in longitudinal studies.

P-glycoprotein gene MDR1 polymorphisms and susceptibility to systemic lupus erythematosus in Guangxi population: a case-control study

The multidrug resistance 1 gene (MDR1) encodes for P-glycoprotein (P-gp), which plays a pathophysiological role in the development of autoimmune diseases, including systemic lupus erythematosus (SLE). Herein, we aimed to investigate the relationship between MDR1 gene polymorphisms and SLE susceptibility in the Chinese Guangxi population. The genotypes of rs1128503 and rs1045642 in MDR1 gene were analyzed using the polymerase chain reaction-restriction fragment length polymorphism method in 283 SLE patients and 247 healthy controls from Guangxi. Direct sequencing method was used to verify the results. Binary logistic regression analyses adjusting for gender and age indicated that subjects carrying the rs1128503 T-allele and TT genotype were at increased risk of SLE when compared to carriers of the C allele and CC genotype, with adjusted ORs of 1.36 (95% CI 1.07-1.74; P = 0.014) and 1.77 (95% CI 1.08-2.88; P = 0.022), respectively. In addition, the risk allele T had a recessive effect (OR 1.49, 95% CI 1.04-2.14, P = 0.029). Subgroup analyses revealed effect modification by age for the presence of the rs1128503 T allele, yielding a significant positive association with SLE in older (≥40 years) subjects (T vs. C allele: OR 1.41, 95% CI 1.01-1.96; P = 0.041; TT vs. CC genotype: OR 1.74, 95% CI 1.07-2.79; P = 0.021). For the first time, we demonstrated that MDR1 rs1128503 polymorphisms were associated with SLE susceptibility in Chinese Guangxi population.

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.

Persistent expression and function of P-glycoprotein on peripheral blood lymphocytes identifies corticosteroid resistance in patients with systemic lupus erythematosus

Corticosteroids (CS) are the mainstay of treatment in systemic lupus erythematosus (SLE) patients. However, some patients have poor response to CS treatment. Among the multiple mechanisms of CS resistance, overexpression of P-glycoprotein (P-gp) on peripheral blood lymphocytes (PBL) may be one of them as this result in efflux of CS from lymphocytes. Thus, we evaluated the role of P-gp protein on PBLs in patients with SLE in its response to CS therapy. SLE patients (n = 42) (fulfilling ACR revised criteria) who were naïve to CS and immunosuppressive drugs were enrolled. Disease activity was assessed using SLE disease activity index (SLEDAI) and expression, and function of P-gp was evaluated by flow cytometry at baseline and after 3 months of therapy with CS. At 3 months, patients with SLEDAI >4 and SLEDAI ≤4 were grouped as nonresponders and responders, respectively. P-gp expression was significantly increased on PBLs of SLE patients as compared to healthy controls (p < 0.001). P-gp expression and function correlated with SLEDAI (r = 0.49, p = 0.005; and r = 0.49, p = 0.001, respectively). P-gp expression and function were not different in responders and nonresponders at baseline. However, at 3 months of CS therapy, P-gp expression and function decreased in responders (p < 0.001 and p < 0.005, respectively), whereas in nonresponders, it remained unchanged. Persistent overexpression and activity of P-gp are associated with poor response to CS in CS naïve patients of SLE.

Review of clinical studies of Polygonum multiflorum Thunb. and its isolated bioactive compounds

Polygonum multiflorum Thunb. (PMT), officially listed in the Chinese Pharmacopoeia, is one of the most popular perennial Chinese traditional medicines known as He shou wu in China and East Asia, and as Fo-ti in North America. Mounting pharmacological studies have stressed out its key benefice for the treatment of various diseases and medical conditions such as liver injury, cancer, diabetes, alopecia, atherosclerosis, and neurodegenerative diseases as well. International databases such as PubMed/Medline, Science citation Index and Google Scholar were searched for clinical studies recently published on P. multiflorum. Various clinical studies published articles were retrieved, providing information relevant to pharmacokinetics-pharmacodynamics analysis, sleep disorders, dyslipidemia treatment, and neurodegenerative diseases. This review is an effort to update the clinical picture of investigations ever carried on PMT and/or its isolated bio-compounds and to enlighten its therapeutic assessment.

Nature and uses of fluorescent dyes for drug transporter studies

INTRODUCTION

Drug transporters are now recognized as major players involved in pharmacokinetics and toxicology. Methods for assessing their activity are important to consider, particularly owing to regulatory requirements with respect to inhibition of drug transporter activity and prediction of drug-drug interactions. In this context, the use of fluorescent-dye-based transport assays is likely to deserve attention.

AREAS COVERED

This review provides an overview of the nature of fluorescent dye substrates for ATP-binding cassette and solute carrier drug transporters. Their use for investigating drug transporter activity in cultured cells and clinical hematological samples, drug transporter inhibition, drug transporter imaging and drug transport at the organ level are summarized.

EXPERT OPINION

A wide range of fluorescent dyes is now available for use in various aspects of drug transporter studies. The use of these dyes for transporter analyses may, however, be hampered by classic pitfalls of fluorescence technology, such as quenching. Transporter-independent processes such as passive diffusion of dyes through plasma membrane or dye sequestration into subcellular compartments must also be considered, as well as the redundant handling by various distinct transporters of some fluorescent probes. Finally, standardization of dye-based transport assays remains an important on-going issue.

Differential alteration in peripheral T-regulatory and T-effector cells with change in P-glycoprotein expression in Childhood Nephrotic Syndrome: A longitudinal study

INTRODUCTION

Childhood Idiopathic Nephrotic Syndrome (INS) responds to glucocorticoid therapy, however, 60-80% of patients relapse and some of them become steroid non responsive. INS may occur because of T cell dysfunction, abnormal cytokines and podocytopathies which reverse on steroid treatment. The reason of relapses could be imbalances in T cells phenotypes and respective cytokines. Herein, we hypothesize that relapses in INS may occur due to imbalance in T-regulatory and T-effector cell with their respective cytokines and overexpression of P-gp on lymphocytes.

METHODS

The frequency of peripheral blood CD4(+)CD25(+)FoxP3(+) Treg, CD4(+)IFN-γ(+) Th1 and CD4(+)IL-4(+) Th2 lymphocytes and their respective cytokines and P-gp expression on peripheral blood lymphocytes (PBLs) were analyzed in INS patients at baseline (n=26), during remission (n=24) and at relapse (n=15).

RESULTS

Compared to baseline, the frequency of Tregs was significantly increased at remission and decreased during relapse. In contrast, the frequency of Th1 and Th2 lymphocytes was significantly decreased during remission and increased at the time of relapse. Similarly, expression of P-gp was significantly high at baseline and at the time of relapse as compared to remission. Levels of cytokines IL-10 and TGF-β in the supernatant of stimulated PBMCs was increased during remission and decreased during relapse. In contrast, levels of IFN-γ and IL-4 were decreased during remission and increased at the time of relapse.

CONCLUSIONS

Steroid therapy in INS induces decreased P-gp expression on PBLs along with increased frequency and cytokine response of T-regulatory cells, and reduced frequency and respective cytokine response of Th1 and Th2 cells during remission. However, reversal in the frequency and respective cytokines of T-regs, Th1 and Th2, and P-gp expression on PBLs occurs during relapses on follow-up.

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.