Uptake of chloroquine and hydroxychloroquine by human blood leucocytes in vitro: relation to cellular concentrations during antirheumatic therapy

Therapeutic drug monitoring of disease-modifying antirheumatic drugs in circulating leukocytes in immune-mediated inflammatory diseases

The treatment of immune-mediated inflammatory diseases (IMIDs) is one of the main challenges of modern medicine. Although a number of disease-modifying antirheumatic drugs (DMARDs) are available, there is wide variability in clinical response to treatment among individuals. Therapeutic drug monitoring (TDM) has been proposed to optimize treatment; however, some patients still experience unsatisfactory outcomes, although the blood concentrations of drugs in these patients remain in the therapeutic range. One possible reason for this is that the conventional samples (e.g., whole blood or plasma) used in TDM may not accurately reflect drug concentrations or concentrations of their metabolites at the target site. Hence, more refined TDM approaches to guide clinical decisions related to dose optimization are necessary. Circulating leukocytes or white blood cells have a critical role in driving the inflammatory process. They are recruited to the site of injury, infection and inflammation, and the main target of small molecule DMARDs is within immune cells. Given this, assaying drug concentrations in leukocytes has been proposed to be of possible relevance to the interpretation of outcomes. This review focuses on the clinical implications and challenges of drug monitoring of DMARDs in peripheral blood leukocytes from therapeutic or toxicological perspectives in IMIDs.

Ameliorating hydroxychloroquine induced retinal toxicity through cerium oxide nanoparticle treatments

The present study investigated the potential protective effects of cerium oxide nanoparticles (CNP) on human retinal pigment epithelium (ARPE-19) cells damaged by hydroxychloroquine (HCQ). Toxicity of HCQ on the ARPE-19 cells was explored with a dose response trial. CNP rescue both a pre-treatment protocol, where CNP were applied 24 hours prior to HCQ application and a simultaneous treatment protocol where both CNP and HCQ were applied together, were used. In the dose response trial, 250 µM HCQ showed 51.84% cell viability after 24 hours and 32.75% after 48 hours time period. This was selected as model HCQ dose for rescue trials. The simultaneous treatment trials did not show a significant increase in viability compared to model toxic dose. The CNP pre-treatment trials showed a significant increase in cellular viability compared to model toxic dose with 68.03% ± 3.27 viability (p = 4.56E-05) at 24 hours and 51.85% ± 4.96 (p = 1.18E-05) at 48 hours time period. CNP pre-treatment showed significant protection of cells from HCQ induced toxicity. The difference in efficacy of simultaneous and pre-treatment is hypothesized to lie in the cellular localization of CNP. Furthermore, including the reactive oxygen species (ROS) scavenging properties of CNP seems to be responsible for protection, the effect of CNP on autophagosome and lysosome colocalization are also hypothesized to play a significant role.

Multi-Compartment Lymph-Node-on-a-Chip Enables Measurement of Immune Cell Motility in Response to Drugs

Organs On-a-Chip represent novel platforms for modelling human physiology and disease. The lymph node (LN) is a relevant immune organ in which B and T lymphocytes are spatially organized in a complex architecture, and it is the place where the immune response initiates. The present study addresses the utility of a recently designed LN-on-a-chip to dissect and understand the effect of drugs delivered to cells in a fluidic multicellular 3D setting that mimics the human LN. To do so, we analyzed the motility and viability of human B and T cells exposed to hydroxychloroquine (HCQ). We show that the innovative LN platform, which operates at a microscale level, allows real-time monitoring of co-cultured B and T cells by imaging, and supports cellular random movement. HCQ delivered to cells through a constant and continuous flow induces a reduction in T cell velocity while promotes persistent rotational motion. We also find that HCQ increases the production of reactive oxygen species in T cells. Taken together, these results highlight the potential of the LN-on-a-chip to be applied in drug screening and development, and in cellular dynamics studies.

Hydroxychloroquine Inhibits the Trained Innate Immune Response to Interferons

Hydroxychloroquine is being investigated for a potential prophylactic effect in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, but its mechanism of action is poorly understood. Circulating leukocytes from the blood of coronavirus disease 2019 (COVID-19) patients show increased responses to Toll-like receptor ligands, suggestive of trained immunity. By analyzing interferon responses of peripheral blood mononuclear cells from healthy donors conditioned with heat-killed Candida, trained innate immunity can be modeled in vitro. In this model, hydroxychloroquine inhibits the responsiveness of these innate immune cells to virus-like stimuli and interferons. This is associated with a suppression of histone 3 lysine 27 acetylation and histone 3 lysine 4 trimethylation of inflammation-related genes, changes in the cellular lipidome, and decreased expression of interferon-stimulated genes. Our findings indicate that hydroxychloroquine inhibits trained immunity in vitro, which may not be beneficial for the antiviral innate immune response to SARS-CoV-2 infection in patients.

PBMCs of COVID-19 patients show increased responses to Toll-like receptor ligands

Trained immunity is modeled in vitro using Candida-trained PBMCs

Hydroxychloroquine inhibits changes in lipidome and histone modifications

Hydroxychloroquine dampens the trained response to interferons and viral stimuli

Elucidating the Pivotal Immunomodulatory and Anti-Inflammatory Potentials of Chloroquine and Hydroxychloroquine

Chloroquine (CQ) and hydroxychloroquine (HCQ) are derivatives of 4-aminoquinoline compounds with over 60 years of safe clinical usage. CQ and HCQ are able to inhibit the production of cytokines such as interleukin- (IL-) 1, IL-2, IL-6, IL-17, and IL-22. Also, CQ and HCQ inhibit the production of interferon- (IFN-) α and IFN-γ and/or tumor necrotizing factor- (TNF-) α. Furthermore, CQ blocks the production of prostaglandins (PGs) in the intact cell by inhibiting substrate accessibility of arachidonic acid necessary for the production of PGs. Moreover, CQ affects the stability between T-helper cell (Th) 1 and Th2 cytokine secretion by augmenting IL-10 production in peripheral blood mononuclear cells (PBMCs). Additionally, CQ is capable of blocking lipopolysaccharide- (LPS-) triggered stimulation of extracellular signal-modulated extracellular signal-regulated kinases 1/2 in human PBMCs. HCQ at clinical levels effectively blocks CpG-triggered class-switched memory B-cells from differentiating into plasmablasts as well as producing IgG. Also, HCQ inhibits cytokine generation from all the B-cell subsets. IgM memory B-cells exhibits the utmost cytokine production. Nevertheless, CQ triggers the production of reactive oxygen species. A rare, but serious, side effect of CQ or HCQ in nondiabetic patients is hypoglycaemia. Thus, in critically ill patients, CQ and HCQ are most likely to deplete all the energy stores of the body leaving the patient very weak and sicker. We advocate that, during clinical usage of CQ and HCQ in critically ill patients, it is very essential to strengthen the CQ or HCQ with glucose infusion. CQ and HCQ are thus potential inhibitors of the COVID-19 cytokine storm.

Chloroquine inhibits human CD4+ T-cell activation by AP-1 signaling modulation

Chloroquine (CQ) is widely used as an anti-inflammatory therapeutic for rheumatic diseases. Although its modes of action on the innate immune system are well described, there is still insufficient knowledge about its direct effects on the adaptive immune system. Thus, we evaluated the influence of CQ on activation parameters of human CD4⁺ T-cells. CQ directly suppressed proliferation, metabolic activity and cytokine secretion of T-cells following anti-CD3/anti-CD28 activation. In contrast, CQ showed no effect on up-regulation of T-cell activation markers. CQ inhibited activation of all T helper cell subsets, although IL-4 and IL-13 secretion by Th2 cells were less influenced compared to other Th-specific cytokines. Up to 10 μM, CQ did not reduce cell viability, suggesting specific suppressive effects on T-cells. These properties of CQ were fully reversible in re-stimulation experiments. Analyses of intracellular signaling showed that CQ specifically inhibited autophagic flux and additionally activation of AP-1 by reducing phosphorylation of c-JUN. This effect was mediated by inhibition of JNK catalytic activity. In summary, we characterized selective and reversible immunomodulatory effects of CQ on human CD4⁺ T-cells. These findings provide new insights into the biological actions of JNK/AP-1 signaling in T-cells and may help to expand the therapeutic spectrum of CQ.

Therapy and pharmacological properties of hydroxychloroquine and chloroquine in treatment of systemic lupus erythematosus, rheumatoid arthritis and related diseases

OBJECTIVES

This review examines the pharmacokinetics, modes of action and therapeutic properties of the anti-malarial drugs, hydroxychloroquine (HCQ) and chloroquine (CQ), in the treatment of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and related conditions, as well as osteoarthritis (OA).

KEY FINDINGS

Both HCQ and CQ have historically been employed successfully for the treatment of SLE and RA for over 70 years. HCQ has been used extensively for SLE where it has a good reputation for controlling the dermatological complications in SLE. It has also been reported to effectively control the symptoms of Sjøgren's syndrome, as well as preventing thrombosis in phospholipid antibody (aPL) syndrome. In RA and SLE, HCQ is preferred because of the lower incidence of gastrointestinal adverse reactions compared with CQ and it might have a lower risk of ocular adverse reactions. There is increasing evidence that HCQ may reduce atherosclerosis and risks of cardiovascular disease in rheumatic patients. Both HCQ and CQ have been shown to improve glycaemia and reduce the risks of type II diabetes mellitus. Although both HCQ and CQ are effective in low-moderate RA, HCQ is now preferred as part of combination therapy for more severe disease. The advantages of combination therapy are that the doses of the individual drugs may be lowered so reducing adverse reactions. Both HCQ and CQ are diastereoisomers, have basic properties and are given as the sulphate and phosphate salts. While being relatively well absorbed orally and with good bioavailability, they have long and variable plasma terminal elimination half-lives (approximately 40-60 days). This reflects their high volume of distribution, V D (HCQ 44,000L; CQ 65,000L) which extends into aqueous compartments, long mean residence time (HCQ 1300 h; CQ 900 h) and with about half the drugs (metabolites) undergoing renal clearance. The strong binding to melanin reflects the ocular injury and dermatological properties of these drugs. The consensus is that the occurrence of ocular adverse reactions can be minimised by close attention to the dose (which should be set on a body weight basis) with regular (e.g. quarterly) retinal examination. Although HCQ and CQ can pass through the placenta, the use of these drugs during pregnancy does not appear to risk harm to the baby and might be beneficial to the mother with SLE and her child by controlling the SLE disease activity, which is known to be an important factor affecting pregnancy outcome. The modes of action of HCQ and CQ in these arthritides represent somewhat of an enigma. Undoubtedly, these drugs have multiple actions related, in part, their ability to accumulate in lysosomes and autophagosomes of phagocytic cells as well as affecting MHC Class II expression and antigen presentation; actions of the production of pro-inflammatory cytokines [e.g. interleukin-1 (IL-1) tumour necrosis factor-α (TNFα)]; control of toll-like receptor-9 activation; and leucocyte generation of reactive oxygen species (ROS); i.e. antioxidant activity. The actions of these drugs on T and B cells are less clear but may depend on these leucocyte-mediated actions. Anti-malarials also protect against cytokine-mediated cartilage resorption. This and other actions may underlie the potential benefits in treating OA. The exact relationships of these various actions, mostly determined in vitro, have not been specifically defined in vivo or ex vivo in relation to clinical efficacy.

OUTCOMES

HCQ and CQ have a good reputation for being effective and relatively safe treatments in SLE, mild-moderate RA and Sjøgren's syndrome. There is need for (a) more information on their mode of action in relation to the control of these diseases, (b) scope for developing formulations that have improved pharmacokinetic and therapeutic properties and safety, and (c) further exploring their use in drug combinations not only with other disease modifying agents but also with biologics.

The enigma of the clandestine association between chloroquine and HIV-1 infection

OBJECTIVES

The antimalarial drug chloroquine (CQ) dampens the immune system and is used in the treatment of autoimmune disorders. CQ also shows antiviral activity against nonenveloped and enveloped viruses, including HIV-1. Persistent immune activation in chronic HIV-1infection leads to CD4 T-cell depletion. CQ is envisioned to attenuate immune activation and virus activity in HIV-1-infected patients. The role of CQ in immune activation and virus activity is discussed here.

METHODS

To elucidate the effect of CQ on immune activation, a retrospective review of published clinical trials, in vivo experimental studies in animals, and the most relevant in vitro observations in HIV-1-infected cells, together with observations from our own laboratory studies, was carried out and the findings discussed.

RESULTS

In a few clinical studies and animal experiments, CQ was ineffective in decreasing immune activation and HIV-1 infection. In vitro, CQ markedly increased HIV-1 infection in astrocytes and other non-CD4 cells.

CONCLUSIONS

The use of CQ in HIV-1-infected patients is questionable. The evidence for a dampening of immune activation by CQ is inconclusive.

Identification and characterisation of small molecule inhibitors of feline coronavirus replication

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Chloroquine, mefloquine, and hexamethylene amiloride demonstrated marked inhibition of FIPV viral replication.

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All three compounds acted at an early stage of viral replication.

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A cost effective resazurin-based cytopathic effect inhibition assay was developed for screening compounds.

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These antiviral compounds, warrant further investigation for clinical use in cats with FIP.

Feline infectious peritonitis (FIP), a feline coronavirus (FCoV) induced disease, is almost invariably fatal with median life expectancy measured in days. Current treatment options are, at best, palliative. The objectives of this study were to evaluate a panel of nineteen candidate compounds for antiviral activity against FCoV in vitro to determine viable candidates for therapy. A resazurin-based cytopathic effect inhibition assay, which detects viable cells through their reduction of the substrate resazurin to fluorescent resorufin, was developed for screening compounds for antiviral efficacy against FCoV. Plaque reduction and virus yield reduction assays were performed to confirm antiviral effects of candidate compounds identified during screening, and the possible antiviral mechanisms of action of these compounds were investigated using virucidal suspension assays and CPE inhibition and IFA-based time of addition assays. Three compounds, chloroquine, mefloquine, and hexamethylene amiloride demonstrated marked inhibition of virus induced CPE at low micromolar concentrations. Orthogonal assays confirmed inhibition of CPE was associated with significant reductions in viral replication. Selectivity indices calculated based on in vitro cytotoxicity screening and reductions in extracellular viral titre were 217, 24, and 20 for chloroquine, mefloquine, and hexamethylene amiloride respectively. Preliminary experiments performed to inform the antiviral mechanism of the compounds demonstrated all three acted at an early stage of viral replication. These results suggest that these direct acting antiviral compounds, or their derivatives, warrant further investigation for clinical use in cats with FIP.

Identification of activators of ERK5 transcriptional activity by high-throughput screening and the role of endothelial ERK5 in vasoprotective effects induced by statins and antimalarial agents

Because ERK5 inhibits endothelial inflammation and dysfunction, activating ERK5 might be a novel approach to protecting vascular endothelial cells (ECs) against various pathological conditions of the blood vessel. We have identified small molecules that protect ECs via ERK5 activation and determined their contribution to preventing cardiac allograft rejection. Using high-throughput screening, we identified certain statins and antimalarial agents including chloroquine, hydroxychloroquine, and quinacrine as strong ERK5 activators. Pitavastatin enhanced ERK5 transcriptional activity and Kruppel-like factor-2 expression in cultured human and bovine ECs, but these effects were abolished by the depletion of ERK5. Chloroquine and hydroxychloroquine upregulated ERK5 kinase activity and inhibited VCAM-1 expression in an ERK5-dependent but MAPK/ERK kinase 5- and Kruppel-like factor 2/4-independent manner. Leukocyte rolling and vascular reactivity were used to evaluate endothelial function in vivo, and we found that EC-specific ERK5 knockout (ERK5-EKO) mice exhibited increased leukocyte rolling and impaired vascular reactivity, which could not be corrected by pitavastatin. The role of endothelial ERK5 in acute cardiac allograft rejection was also examined by heterotopic grafting of the heart obtained from either wild-type or ERK5-EKO mice into allomismatched recipient mice. A robust increase in both inflammatory gene expression and CD45-positive cell infiltration into the graft was observed. These tissue rejection responses were inhibited by pitavastatin in wild-type but not ERK5-EKO hearts. Our study has identified statins and antimalarial drugs as strong ERK5 activators and shown that ERK5 activation is preventive of endothelial inflammation and dysfunction and acute allograft rejection.

Novel small molecule inhibitors of TLR7 and TLR9: mechanism of action and efficacy in vivo

The discovery that circulating nucleic acid-containing complexes in the serum of autoimmune lupus patients can stimulate B cells and plasmacytoid dendritic cells via Toll-like receptors 7 and 9 suggested that agents that block these receptors might be useful therapeutics. We identified two compounds, AT791 {3-[4-(6-(3-(dimethylamino)propoxy)benzo[d]oxazol-2-yl)phenoxy]-N,N-dimethylpropan-1-amine} and E6446 {6-[3-(pyrrolidin-1-yl)propoxy)-2-(4-(3-(pyrrolidin-1-yl)propoxy)phenyl]benzo[d]oxazole}, that inhibit Toll-like receptor (TLR)7 and 9 signaling in a variety of human and mouse cell types and inhibit DNA-TLR9 interaction in vitro. When administered to mice, these compounds suppress responses to challenge doses of cytidine-phosphate-guanidine (CpG)-containing DNA, which stimulates TLR9. When given chronically in spontaneous mouse lupus models, E6446 slowed development of circulating antinuclear antibodies and had a modest effect on anti-double-stranded DNA titers but showed no observable impact on proteinuria or mortality. We discovered that the ability of AT791 and E6446 to inhibit TLR7 and 9 signaling depends on two properties: weak interaction with nucleic acids and high accumulation in the intracellular acidic compartments where TLR7 and 9 reside. Binding of the compounds to DNA prevents DNA-TLR9 interaction in vitro and modulates signaling in vivo. Our data also confirm an earlier report that this same mechanism may explain inhibition of TLR7 and 9 signaling by hydroxychloroquine (Plaquenil; Sanofi-Aventis, Bridgewater, NJ), a drug commonly prescribed to treat lupus. Thus, very different structural classes of molecules can inhibit endosomal TLRs by essentially identical mechanisms of action, suggesting a general mechanism for targeting this group of TLRs.

Chloroquine modulates the fungal immune response in phagocytic cells from patients with chronic granulomatous disease

Invasive aspergillosis is a major threat to patients with chronic granulomatous disease (CGD). Fungal pathogenesis is the result of a diminished antifungal capacity and dysregulated inflammation. A deficient NADPH-oxidase complex results in defective phagolysosomal alkalization. To investigate the contribution of defective pH regulation in phagocytes among patients with CGD during fungal pathogenesis, we evaluated the effect of the acidotropic, antimalarial drug chloroquine (CQ) on the antifungal capacity of polymorphonuclear cells (PMNs) and on the inflammatory response of peripheral blood mononuclear cells (PBMCs). Chloroquine exerted a direct pH-dependent antifungal effect on Aspergillus fumigatus and Aspergillus nidulans; it increased the antifungal activity of PMNs from patients with CGD at a significantly lower concentration, compared with the concentration for PMNs from healthy individuals; and decreased the hyperinflammatory state of PBMCs from patients with CGD, as observed by decreased tumor necrosis factor α and interleukin 1β release. Chloroquine targets both limbs of fungal pathogenesis and might be of great value in the clearance of invasive aspergillosis in patients with CGD.

The presence of leukocytes in ex vivo assays significantly increases the 50-percent inhibitory concentrations of artesunate and chloroquine against Plasmodium vivax and Plasmodium falciparum

Plasmodium species ex vivo sensitivity assay protocols differ in the requirement for leukocyte removal before culturing. This study shows that the presence of leukocytes significantly increases the 50% inhibitory concentration (IC₅₀) of P. vivax and P. falciparum to artesunate and chloroquine relative to results with the paired leukocyte-free treatment. Although leukocyte removal is not an essential requirement for the conduct of ex vivo assays, its use has important implications for the interpretation of temporal and spatial antimalarial sensitivity data.

Immunomodulatory drugs regulate HMGB1 release from activated human monocytes

Several HMGB1-specific antagonists have provided beneficial results in multiple models of inflammatory disease-preclinical trials including arthritis. Since no HMGB1-specific targeted therapy has yet reached the clinic, we have performed in vitro studies to investigate whether any of a selection of well-established antirheumatic drugs inhibit HMGB1 release as part of its mode of action. Freshly purified peripheral blood monocytes from healthy donors were stimulated in cultures with LPS and IFNγ to cause HMGB1 and TNF release detected in ELISPOT assays. Effects on the secretion were assessed in cultures supplemented with dexamethasone, cortisone, chloroquine, gold sodium thiomalate, methotrexate, colchicine, etanercept or anakinra. Pharmacologically relevant doses of dexamethasone, gold sodium thiomalate and chloroquine inhibited the extracellular release of HMGB1 in a dose-dependent mode. Immunostaining demonstrated that dexamethasone caused intracellular HMGB1 retention. No effects on HMGB1 secretion were observed in cultures with activated monocytes by any of the other studied agents. TNF production in LPS/IFNγ-activated monocytes was readily downregulated by dexamethasone and, to some extent, by chloroquine and etanercept. We conclude that dexamethasone, gold sodium thiomalate and chloroquine share a capacity to inhibit HMGB1 release from activated monocytes.

Chloroquine modulates HIV-1-induced plasmacytoid dendritic cell alpha interferon: implication for T-cell activation

Plasmacytoid dendritic cells (pDC) contribute to antiviral immunity mainly through recognition of microbial products and viruses via intracellular Toll-like receptor 7 (TLR7) or TLR9, resulting in the production of type I interferons (IFNs). Although interferons reduce the viral burden in the acute phase of infection, their role in the chronic phase is unclear. The presence of elevated plasma IFN-alpha levels in advanced HIV disease and its association with microbial translocation in chronic HIV infection lead us to hypothesize that IFN-alpha could contribute to immune activation. Blocking of IFN-alpha production using chloroquine, an endosomal inhibitor, was tested in a novel in vitro model system with the aim of characterizing the effects of chloroquine on HIV-1-mediated TLR signaling, IFN-alpha production, and T-cell activation. Our results indicate that chloroquine blocks TLR-mediated activation of pDC and MyD88 signaling, as shown by decreases in the levels of the downstream signaling molecules IRAK-4 and IRF-7 and by inhibition of IFN-alpha synthesis. Chloroquine decreased CD8 T-cell activation induced by aldrithiol-2-treated HIV-1 in peripheral blood mononuclear cell cultures. In addition to blocking pDC activation, chloroquine also blocked negative modulators of the T-cell response, such as indoleamine 2,3-dioxygenase (IDO) and programmed death ligand 1 (PDL-1). Our results indicate that TLR stimulation and production of IFN-alpha by pDC contribute to immune activation and that blocking of these pathways using chloroquine may interfere with events contributing to HIV pathogenesis. Our results suggests that a safe, well-tolerated drug such as chloroquine can be proposed as an adjuvant therapeutic candidate along with highly active antiretroviral therapy to control immune activation in HIV-1 infection.

Prediction of drug distribution within blood

Drug distribution in blood, defined as drug blood-to-plasma concentration ratio (R(b)), is a fundamental pharmacokinetic parameter. It relates the plasma clearance to the blood clearance, enabling the physiological interpretation of this parameter. Although easily experimentally determined, R(b) values are lacking for the vast majority of drugs. We present a systematic approach using mechanistic, partial least squares (PLS) regression and artificial neural network (ANN) models to relate various in vitro and in silico molecular descriptors to a dataset of 93 drug R(b) values collected in the literature. The ANN model resulted in the best overall approach, with r(2)=0.927 and r(2)=0.871 for the train and the test sets, respectively. PLS regression presented r(2)=0.557 for the train and r(2)=0.656 for the test set. The mechanistic model provided the worst results, with r(2)=0.342 and, additionally, is limited to drugs with a basic ionised group with pKa<7. The ANN model for drug distribution in blood can be a valuable tool in clinical pharmacokinetics as well as in new drug design, providing predictions of R(b) with a percentage of correct values within a 1.25-fold error of 86%, 84% and 87% in the train, test and validation set of data.

Hydroxychloroquine potentiates Fas-mediated apoptosis of rheumatoid synoviocytes

Inadequate apoptosis may contribute to the synovial hyperplasia associated with rheumatoid arthritis (RA). The Fas-associated death domain protein (FADD)-like interleukin (IL)-1beta-converting enzyme (FLICE)-inhibitory protein (FLIP), which is an apoptotic inhibitor, has been implicated in the resistance to Fas-mediated apoptosis of synoviocytes. This study investigated whether hydroxychloroquine (HCQ), an anti-rheumatic drug, induces the apoptosis of rheumatoid synoviocytes, and modulates the expression of FLIP. Fibroblast-like synoviocytes (FLS) were prepared from the synovial tissues of RA patients, and were cultured with various concentrations of HCQ in the presence or absence of the IgM anti-Fas monoclonal antibodies (mAb) (CH11). Treatment with HCQ, ranging from 1 to 100 microM, induced the apoptosis of FLS in a dose- and time-dependent manner. The increase in synoviocytes apoptosis by HCQ was associated with caspase-3 activation. A combined treatment of HCQ and anti-Fas mAb increased FLS apoptosis and caspase-3 activity synergistically, compared with either anti-Fas mAb or HCQ alone. The Fas expression level in the FLS was not increased by the HCQ treatment, while the FLIP mRNA and protein levels were decreased rapidly by the HCQ treatment. Moreover, time kinetics analysis revealed that the decreased expression of FLIP by HCQ preceded the apoptotic event that was triggered by HCQ plus anti-Fas mAb. Taken together, HCQ increases the apoptosis of rheumatoid synoviocytes by activating caspase-3, and also sensitizes rheumatoid synoviocytes to Fas-mediated apoptosis. Our data suggest that HCQ may exert its anti-rheumatic effect in rheumatoid joints through these mechanisms.

Chloroquine inhibits production of TNF-alpha, IL-1beta and IL-6 from lipopolysaccharide-stimulated human monocytes/macrophages by different modes

OBJECTIVES

TNF-alpha, IL-1 and IL-6 are known to have primary roles in the pathogenesis of rheumatoid arthritis and other inflammatory diseases. The anti-rheumatic drug chloroquine has been shown to inhibit TNF-alpha, IL-1 and IL-6 production from mononuclear phagocytes. We examined the underlying mechanisms involved in the chloroquine-induced inhibition of cytokine production.

METHODS

Human peripheral blood mononuclear cells and monocytes/macrophages and monocytic U-937 and THP-1 cells were stimulated with lipopolysaccharide, and TNF-alpha, IL-1beta and IL-6 production was measured by ELISA. Levels of mRNA were measured by northern blotting and reverse transcription-polymerase chain reaction. Synthesis of 26-kDa TNF-alpha precursor was measured by metabolic labelling and immunoprecipitation analysis. Transcription rate was determined by nuclear run-on assay.

RESULTS

TNF-alpha release from the cells was inhibited by chloroquine, whereas the steady-state level of TNF-alpha mRNA and synthesis of 26-kDa TNF-alpha precursor were not changed by chloroquine. In contrast, chloroquine-induced inhibition of IL-1beta and IL-6 release was accompanied by a decrease in their steady-state mRNA levels. The transcription rates of the IL-1beta and IL-6 genes were not changed by chloroquine, whereas the stability of IL-1beta and IL-6 mRNA was decreased by chloroquine. Weak-base amines such as methylamine and ammonium chloride had no effect on the production of TNF-alpha, whereas they partially blocked the production of IL-1beta and IL-6.

CONCLUSIONS

Our results indicate that chloroquine-mediated inhibition of TNF-alpha, IL-1beta and IL-6 synthesis occurs through different modes in lipopolysaccharide-stimulated human monocytes/macrophages: it blocks the conversion of cell-associated TNF-alpha precursor to mature soluble protein, whereas it reduces the levels of IL-1beta and IL-6 mRNA, at least in part, by decreasing their stability and by a pH-dependent mechanism.

Hydroxychloroquine, hydroxyurea and didanosine as initial therapy for HIV-infected patients with low viral load: safety, efficacy and resistance profile after 144 weeks

OBJECTIVES

To evaluate the long-term safety and efficacy of the combination of hydroxychloroquine, hydroxyurea and didanosine.

METHODS

We recruited antiretroviral-naive patients with viral loads less than 100 000 HIV-1 RNA copies/mL and CD4 counts greater than 150 cells/microL. All patients received hydroxychloroquine (200 mg), hydroxyurea (500 mg) and didanosine (125-200 mg) twice daily. Clinical and laboratory safety assessments and measurements of viral load and CD4 count were made at regular intervals, and genotypic resistance testing was performed on samples with detectable viral load at 48, 96 and 144 weeks.

RESULTS

Fourteen of the 17 patients who commenced therapy remained on treatment at 144 weeks. Treatment was well tolerated but caused neutropenia, usually mild and transient, in 12 patients (71%). Mean viral load was reduced by 1.6 log(10) copies/mL below baseline (P<0.001), eight patients (47%) had undetectable viral load (<400 copies/mL), and two patients (12%) had detectable viral load but no detectable resistance mutations at week 144. Four patients (24%) had detectable viral load together with major resistance mutations (three with both 74 V and 184 V, and one with both 62 V and 65R) at week 144, but still had viral load suppression below baseline. Mean CD4 count was increased by 106 cells/microL above baseline (P=0.07) at week 144.

CONCLUSIONS

This novel and well-tolerated combination controls viral replication during long-term follow up, with development of few resistance mutations. With careful monitoring it may be a useful strategy for delaying highly active antiretroviral therapy (HAART) and associated toxicity in selected patients with low initial viral loads.

Inhibition of mitogen-activated protein kinase signaling by chloroquine

Previously, we demonstrated that the anti-inflammatory drug chloroquine (CQ) inhibited LPS-induced TNF-alpha transcription. To define further the mechanism of CQ, we studied the effect of this drug on mitogen-activated protein kinase signaling pathways involved in regulation of TNF production. CQ interfered with phosphorylation of extracellular signal-regulated kinases (ERK)1/2 and the ERK-activating kinases mitogen-activating protein/ERK kinase (MEK)1/2. Both CQ and PD98059, a MEK1 inhibitor, reduced luciferase reporter activity driven by human TNF promoter sequences. However, CQ appeared to mediate these effects by deactivating Raf, the upstream activator of MEK. These findings were supported by functional data demonstrating that CQ and PD98059 interfered with TNF expression in several human and murine cell types while neither inhibitor blocked TNF production in murine RAW264.7 macrophages, a cell line that does not require MEK-ERK signaling for TNF production. Finally, we evaluated whether CQ could sensitize HeLa cells to undergo anti-Fas-mediated apoptosis, an effect observed when ERK activation is interrupted in this cell line. CQ rendered HeLa cells sensitive to anti-Fas treatment in a manner similar to PD98059. Taken together, these data argue that therapeutic concentrations of CQ interfere with ERK activation by a novel mechanism, an effect that could be responsible, at least in part, for the potent anti-inflammatory effects of this drug.

Cooperation of chloroquine and blood platelets in inhibition of polymorphonuclear leukocyte chemiluminescence

Effect of activated blood platelets and chloroquine on concentration of reactive oxygen species produced by polymorphonuclear leukocytes (PMNL) stimulated with Ca(2+)-ionophore A23187 was investigated. Oxygen metabolites localized outside PMNL were visualized by isoluminol enhanced chemiluminescence, whereas chemiluminescence, enhanced with luminol and measured in the presence of the extracellular scavengers superoxide dismutase and catalase, was used for the detection of radicals originated intracellularly. Significant reduction of chemiluminescence was observed in the presence of platelets (added to PMNL in the physiological cell ratio 50:1) and of chloroquine (10 and 100 micromol/L). Although chloroquine decreased effectively both the extra- as well as the intracellular part of the chemiluminescence signal, the activity of platelets occurred largely outside PMNL. Serotonin liberated from platelets by A23187 appeared to be involved in inhibition of chemiluminescence; its concentrations achieved in platelet supernatants were found to be sufficient for elimination of PMNL-derived oxygen metabolites. The presented results indicated that chloroquine and blood platelets cooperate in inhibition of chemiluminescence because their common effect was found to be much more extensive than reduction induced by these inhibitors separately. Therefore, for accurate prediction of drug effect in the whole organism, the use of multicellular test systems seems to be pertinent.

Western and Chinese antirheumatic drug-induced T cell apoptotic DNA damage uses different caspase cascades and is independent of Fas/Fas ligand interaction

Spontaneous or therapeutic induction of T cell apoptosis plays a critical role in establishing transplantation tolerance and maintaining remission of autoimmune diseases. We investigated the mechanisms of apoptosis induced by Chinese and Western antirheumatic drugs (ARDs) in human T cells. We found that hydroxychloroquine, Tripterygium wilfordii hook F, and tetrandrine (Tet), but not methotrexate, at therapeutic concentrations can cause T cell death. In addition, Tet selectively killed T cells, especially activated T cells. Although ARD-induced cytotoxicity was mediated through apoptotic mechanisms, Fas/Fas ligand interaction was not required. We further demonstrated that the processes of phosphatidylserine externalization and DNA damage along the ARD-induced T cell apoptotic pathway could operate independently, and that selective inhibition of DNA damage by caspase inhibitors did not prevent T cells from undergoing cell death. Moreover, we found that Tet- and Tripterygium wilfordii hook F-induced T cell DNA damage required caspase-3 activity, and hydroxychloroquine-induced T cell DNA damage was mediated through a caspase-3- and caspase-8-independent, but Z-Asp-Glu-Val-Asp-fluomethyl ketone-sensitive, signaling pathway. Finally, the observation that ARD-induced activation of caspase-3 in both Fas-sensitive and Fas-resistant Jurkat T cells indicates that Fas/Fas ligand interaction plays no role in ARD-induced T cell apoptosis. Our observations provide new information about the complex apoptotic mechanisms of ARDs, and have implications for combining Western and Chinese ARDs that have different immunomodulatory mechanisms in the therapy of autoimmune diseases and transplantation rejection.

Early induction of apoptosis in B-chronic lymphocytic leukaemia cells by hydroxychloroquine: activation of caspase-3 and no protection by survival factors

We have investigated the effect of hydroxychloroquine (HCQ), an anti-rheumatic drug, on malignant B cells from 20 patients with B-chronic lymphocytic leukaemia (B-CLL). HCQ induced a decrease in cell viability in a dose- and time-dependent manner. The mean IC50 was 32 +/- 7 microg/ml (range, 10-75 microg/ml) for 24 h of exposure. This cytotoxic effect was owing to apoptosis, as demonstrated by morphological changes, annexin V binding capacity and DNA fragmentation (28 +/- 4% of apoptotic cells as early as 5 h post incubation, increasing to 82 +/- 4% at 18 h post treatment). The apoptosis was associated with caspase-3 activation because the cleavage and activity of caspase-3 were increased by HCQ. The amount of bcl-2 protein was reduced during apoptosis, evidenced using quantitative flow cytometry. As early as 1 h post-HCQ treatment, a reduction of the mitochondrial transmembrane potential was measured by 3,3'-dihexyloxacarbocyanine iodide. Interestingly, the HCQ effect was not affected by exposure to interleukin-4 or co-culture with bone marrow stromal cells. Our observations suggest that HCQ may offer a new therapeutic tool in the treatment of B-CLL patients.

The anti-HIV-1 activity of chloroquine

BACKGROUND

there is a dramatic need for drugs with anti-HIV-1 activity that are affordable for resource-poor countries. Chloroquine (CQ) is one such drug.

OBJECTIVES

to review the data indicating that CQ has anti-HIV-1 activity.

RESULTS

chloroquine (CQ) and its derivative hydroxychloroquine (HCQ) are endowed with a broad anti-HIV-1 activity inhibiting X4, R5, and X4/R5 stains in lymphocytic and monocytic cells. Interestingly, CQ is capable of inhibiting HIV-1 replication at concentrations within the range reported in plasma of individuals chronically treated with doses of the drug which have well-known and limited toxicity. These effects have been confirmed in vivo in two clinical trials. The principal mechanism of HIV-1 inhibition by CQ seems to be an effect on gp120 on a post-transcriptional level. Because CQ and HCQ appear to have a novel site of action (i.e. post-transcriptional inhibition of gp120), these drugs may be particularly useful in combination with other anti-retroviral agents (e.g. ZDV, ddI and HU).

CONCLUSION

combining these drugs with other anti-HIV-1 agents, especially HU and ddI, may be an interesting option for the treatment for HIV-1 infected individuals in the developing world.

Chloroquine interferes with lipopolysaccharide-induced TNF-alpha gene expression by a nonlysosomotropic mechanism

Chloroquine (CQ) is a lysosomotropic weak base with over 60 years of clinical use for the treatment of malaria and rheumatologic disorders. Consistent with its anti-inflammatory properties, CQ has been shown to interfere with TNF-alpha release from mononuclear phagocytes. Because it is unclear how CQ mediates these immunomodulatory effects, we set out to elucidate its mechanism of action. CQ exhibited dose-dependent inhibition of LPS-induced TNF-alpha release from human PBMC at therapeutically attainable concentrations. Additional studies to determine the specificity of this effect showed that although CQ reduced IL-1beta and IL-6 release, secretion of RANTES was unaffected. CQ acted by reducing TNF-alpha mRNA accumulation without destabilizing its mRNA or interfering with NF-kappaB nuclear translocation or p50/p65 isoform composition of DNA-binding complexes. Intracellular cytokine staining indicated that CQ reduced TNF-alpha production pretranslationally without interfering with TNF-alpha processing or release. We utilized bafilomycin A1 pretreatment to block the pH-dependent trapping of CQ in endosomes and lysosomes. Although bafilomycin A1 alone did not interfere with TNF-alpha expression, preincubation augmented the ability of CQ to reduce TNF-alpha mRNA levels, suggesting that CQ did not act by a lysosomotropic mechanism. Using confocal microscopy, we showed that bafilomycin A1 pretreatment resulted in a dramatic redistribution of quinacrine, a fluorescent congener of CQ, from cytoplasmic vacuoles to the nucleus. These data indicate that CQ inhibits TNF-alpha gene expression without altering translocation of NF-kappaB p50/p65 heterodimers. This dose-dependent effect occurs over a pharmacologically relevant concentration range and does not require pH-dependent lysosomotropic accumulation of CQ.

Chloroquine and the fungal phagosome

The antimalarial drug chloroquine accumulates inside the macrophage phagolysosome by ion trapping where it exerts potent antifungal activity against Histoplasma capsulatum and Cryptococcus neoformans by distinct mechanisms. Chloroquine inhibits growth of H. capsulatum by pH-dependent iron deprivation, whereas it is directly toxic to C. neoformans. Clearly, clinical studies are required to document the potential therapeutic efficacy of chloroquine or related congeners as adjuvant therapy in fungal disease. Moreover, the diversity of pathogenic microorganisms inhibited and/or killed by chloroquine makes this drug an attractive candidate for prophylactic therapy.

Hydroxychloroquine reverses thrombogenic properties of antiphospholipid antibodies in mice

BACKGROUND

Previous studies have demonstrated that human monoclonal and polyclonal anticardiolipin antibodies have thrombogenic properties in vivo. Using such a model in which these antibodies have been shown to increase both the size of an induced thrombus and the duration of time in which such a clot lasts, we investigated whether hydroxychloroquine alters the dynamics of such thrombus formation.

METHODS AND RESULTS

Three groups of nine mice were injected with purified immunoglobulin G (IgG) from a patient with the antiphospholipid syndrome (IgG-APS) and then fed with hydroxychloroquine at various doses (100, 6, and 3 mg/kg body wt). Three control groups of mice were also studied, including mice injected with IgG-APS and then fed with placebo, as well as two other groups injected with IgG from normal human serum and fed either hydroxychloroquine or placebo. A standardized thrombogenic injury was subsequently induced in the femoral vein of each mouse and the area (size) of thrombus measured as well as the total period of time that thrombus was present. Mice treated with hydroxychloroquine and IgG-APS showed significantly smaller thrombi that persisted for a shorter period of time compared with animals treated with IgG-APS and placebo.

CONCLUSIONS

Hydroxychloroquine significantly diminished both thrombus size and total time of thrombus formation in mice previously injected with IgG-APS.

Chloroquine induces human mononuclear phagocytes to inhibit and kill Cryptococcus neoformans by a mechanism independent of iron deprivation

Infections due to Cryptococcus neoformans are common in AIDS patients. We investigated the effect of chloroquine, which raises the pH of phagolysosomes, on the anticryptococcal activity of mononuclear phagocytes. C. neoformans multiplied within monocyte-derived macrophages (MDM) in the absence of chloroquine but were killed with the addition of chloroquine. Ammonium chloride was also beneficial, suggesting that effects were mediated by alkalinizing the phagolysosome. Chloroquine inhibits growth of other intracellular pathogens by limiting iron availability. However, chloroquine-induced augmentation of MDM anticryptococcal activity was unaffected by iron nitriloacetate, demonstrating that chloroquine worked by a mechanism independent of iron deprivation. There was an inverse correlation between growth of C. neoformans in cell-free media and pH, suggesting that some of the effect of chloroquine on the anticryptococcal activity of MDM could be explained by relatively poor growth at higher pH. Chloroquine enhanced MDM anticryptococcal activity against all tested cryptococcal strains except for one large-capsule strain which was not phagocytosed. Positive effects of chloroquine were also seen in monocytes from both HIV-infected and -uninfected donors. Finally, chloroquine was therapeutic in experimental cryptococcosis in outbred and severe combined immunodeficient mice. Thus, chloroquine enhances the activity of mononuclear phagocytes against C. neoformans by iron-independent, pH-dependent mechanisms and is therapeutic in murine models of cryptococcosis. Chloroquine might have clinical utility for the prophylaxis and treatment of human cryptococcosis.

Induction of apoptosis in peripheral blood lymphocytes following treatment in vitro with hydroxychloroquine

OBJECTIVE

Defective regulation of apoptosis may be central to the development of autoimmune disorders. This study investigated the possibility that the antirheumatic effect of hydroxycholoroquine (HCQ) may be achieved by up-regulation of apoptosis.

METHODS

Peripheral blood lymphocytes collected from normal controls and patients with systemic lupus erythematosus (SLE) were cultured in the presence or absence of a range of concentrations of HCQ. Cells undergoing apoptosis were identified by several standard methods, including morphologic changes, DNA fragmentation, and flow cytometry. For some experiments, lymphocytes were simultaneously stained with antibodies to T cell surface markers and with propidium iodide for dual-stain flow cytometric studies.

RESULTS

HCQ was able to induce apoptosis in peripheral blood lymphocytes in a dose- and time-dependent manner. HCQ induced these changes in all T cell subpopulations studied. There was no significant difference between the controls and patients with SLE in terms of the percentage of apoptotic cells detected following treatment with HCQ.

CONCLUSION

The present study demonstrated that HCQ induces apoptosis in peripheral blood lymphocytes, which leads to the speculation that HCQ may exert its antirheumatic effect through this mechanism.

Clinical pharmacokinetics and metabolism of chloroquine. Focus on recent advancements

This paper presents the current state of knowledge on chloroquine disposition, with special emphasis on stereoselectivity and microsomal metabolism. In addition, the impact of the patient's physiopathological status and ethnic origin on chloroquine pharmacokinetics is discussed. In humans, chloroquine concentrations decline multiexponentially. The drug is extensively distributed, with a volume of distribution of 200 to 800 L/kg when calculated from plasma concentrations and 200 L/kg when estimated from whole blood data (concentrations being 5 to 10 times higher). Chloroquine is 60% bound to plasma proteins and equally cleared by the kidney and liver. Following administration chloroquine is rapidly dealkylated via cytochrome P450 enzymes (CYP) into the pharmacologically active desethylchloroquine and bisdesethylchloroquine. Desethylchloroquine and bisdesethylchloroquine concentrations reach 40 and 10% of chloroquine concentrations, respectively; both chloroquine and desethylchloroquine concentrations decline slowly, with elimination half-lives of 20 to 60 days. Both parent drug and metabolite can be detected in urine months after a single dose. In vitro and in vivo, chloroquine and desethylchloroquine competitively inhibit CYP2D1/6-mediated reactions. Limited in vitro studies and preliminary data from clinical experiments and observations point to CYP3A and CYP2D6 as the 2 major isoforms affected by or involved in chloroquine metabolism. In vitro efficacy studies did not detect any difference in potency between chloroquine enantiomers but, in vivo in rats, S(+)-chloroquine had a lower dose that elicited 50% of the maximal effect (ED950) than that of R(-)-chloroquine. Stereoselectivity in chloroquine body disposition could be responsible for this discrepancy. Chloroquine binding to plasma proteins is stereoselective, favouring S(+)-chloroquine (67% vs 35% for the R-enantiomer). Hence, unbound plasma concentrations are higher for R(-)-chloroquine. Following separate administration of the individual enantiomers, R(-)-chloroquine reached higher and more sustained blood concentrations. The shorter half-life of S(+)-chloroquine appears secondary to its faster clearance. Blood concentrations of the S(+)-forms of desethylchloroquine always exceeded those of the R(-)-forms, pointing to a preferential metabolism of S(+)-chloroquine.

Hematologic disposition of hydroxychloroquine enantiomers

Hydroxychloroquine (HCQ) is a racemic antiarthritic agent that has a long half-life (t1/2) in plasma and accumulates in blood cells. To study the relationships between HCQ concentrations in plasma, serum, and whole blood and to determine the optimal blood fraction to use for therapeutic drug monitoring of the drug, we studied the relative distribution of the HCQ enantiomers in various fractions of human blood under in vivo and in vitro conditions. Substantially greater concentrations of both enantiomers were found in serum as compared with plasma because of release via platelet activation. After in vitro incubations of the separated blood cells with HCQ, high concentrations of both enantiomers were found in leukocytes, and low concentrations in erythrocytes and platelets; the R:S ratio in vitro was near unity in all of the cells examined. Unlike the in vitro cellular uptake, the concentrations of HCQ in vivo were significantly lower and stereoselective (R:S ratio = 2). There was almost no drug in the polymorphonuclear cells (PMN) in vivo, despite a substantial uptake in vitro after incubation of separated cells. The enantiomeric (R:S) ratio in the urinary excretion of the enantiomers was significantly correlated with that in plasma. The plasma-protein binding of the enantiomers was stereoselective and complimented the cellular uptake findings; the unbound fraction was dependent on the plasma concentrations of alpha 1-acid glycoprotein, but not albumin. Although concentrations in whole blood correlated well with those in lymphocytes and monocytes (the proposed site of HCQ action), stronger correlations were found between concentrations in serum and in the mononuclear cells.

Inhibition of human immunodeficiency virus type 1 replication by hydroxychloroquine in T cells and monocytes

Chloroquine and its analogue hydroxychloroquine (HCQ) have been shown to inhibit a variety of viral infections including influenza and adenovirus through blockade of viral entry via inhibition of endosomal acidification. We have extended these observations to human immunodeficiency virus type 1 (HIV-1) infection utilizing primary T cells and monocytes, a T cell line (CEM), and a monocytic cell line (U-937). HCQ inhibited HIV-1 replication (> 75%), as measured by reverse transcriptase activity, in the primary T cells and monocytes as well as the T cell and monocytic cell lines. HCQ itself had no anti-reverse transcriptase activity and was not toxic to the cells at concentrations inhibitory to viral replication. Intracytoplasmic staining with an anti-p24 antibody, 24 h after infection, revealed the presence of intracytoplasmic virus, suggesting that the drug does not block viral entry. The production of steady-state HIV-1 mRNA was not affected by HCQ in that comparable levels of HIV-1 mRNA could be detected by Northern blot analysis and by in situ hybridization in both the HCQ-treated and untreated cells. However, HCQ does appear to affect production of infectious HIV-1 virions because viral isolates from HCQ-treated cells could not infect target CEM cells. These data suggest that HCQ may be useful adjunctive therapy in the treatment of HIV-1 infection.

Analytical and semi-preparative high-performance liquid chromatographic separation and assay of hydroxychloroquine enantiomers

(+/-)-Hydroxychloroquine (HCQ) is an antimalarial and anti-arthritic drug which is administered as the racemate. An accurate, precise and sensitive high-performance liquid chromatographic assay was developed for the determination of HCQ enantiomers in samples from human plasma, serum, whole blood, and urine. After addition of (+/-)-chloroquine (internal standard), samples of blood component (0.5 ml) or urine (0.1 ml) were alkalinized and extracted with 5 ml of diethyl ether. After solvent evaporation the residues were derivatized with (+)-di-O-acetyl-L-tartaric anhydride at 45 degrees C for 30 min. The resulting diastereomers were then resolved using a C8 analytical column with a mobile phase consisting of 0.05 M KH2PO4 (pH 3)-methanol-ethanol-triethylamine (78:22:1:0.08). The ultraviolet detection wavelength was set at 343 nm. The derivatized HCQ enantiomers eluted in less than 40 min, free of interfering peaks. Excellent linear relationships (r2 > 0.997) were obtained between the area ratios and the corresponding plasma concentrations over a range of 12.5-500 ng/ml. The diastereomers could be hydrolysed using microwave energy and neutral pH, which enabled us to resolve the enantiomers on a semi-preparative (C18 column) scale. The method was suitable for the analysis and semi-preparative separation of HCQ enantiomers.

Inhibition of tubercle bacilli in cultured human macrophages by chloroquine used alone and in combination with streptomycin, isoniazid, pyrazinamide, and two metabolites of vitamin D3

Intracellular tubercle bacilli (TB) reside in vacuoles in infected human macrophages (MPs). The relative impotency of streptomycin against TB in MPs and the contrary greatly increased potency of pyrazinamide (PZA) have been attributed to the fact that these vacuoles are phagolysosomes and, therefore, acidic. Chloroquine (CQ) is a lysomotropic base which can be used to raise phagolysosomal pH. Consequently, it was tested for its ability to increase the anti-TB effectiveness of streptomycin and decrease that of PZA in cultured human MPs. MPs infected with virulent Erdman strain TB were incubated in medium with various combinations of the drugs. Samples were taken at 0, 4, and 7 days and lysed for CFU counts of viable TB on nutrient agar. As expected, CQ increased the effectiveness of SM, but unexpectedly, it did not decrease that of PZA. CQ alone was found to be able to inhibit intracellular TB. Because of this, it was also tested with isoniazid, 1,25(OH)2-vitamin D3, and 25-OH-vitamin D3. It significantly enhanced the anti-TB protectiveness of both isoniazid and 25-OH-vitamin D3. Some combinations of CQ and the various drugs tested were able to kill intracellular TB. These results suggest that CQ may be useful in the treatment of tuberculosis.

Bioavailability of hydroxychloroquine tablets in healthy volunteers

1. Five healthy volunteers received, in a randomised crossover design study, a 155 mg oral tablet and an intravenous infusion of 155 mg racemic hydroxychloroquine (200 mg hydroxychloroquine sulphate) to assess the bioavailability of the commercially available tablet (Plaquenil, Winthrop Laboratories, Australia). 2. The terminal elimination half-life of hydroxychloroquine is more than 40 days, thus blood and urine samples were collected for 5 months following each dose to characterise adequately the terminal elimination phase and obtain accurate estimates of the areas under the concentration-time curves. 3. The mean (+/- s.d.) fraction of the oral dose absorbed, estimated from the blood and urine data, was 0.74 (+/- 0.13). A wide range of estimates of the fraction of the oral dose absorbed was calculated from the plasma data (0.41 - 1.53), reflecting the difficulties of accurate measurement of hydroxychloroquine in plasma. 4. A period of 6 months is required to achieve 96% of steady-state levels of hydroxychloroquine with the usual once daily, oral dosage regimen. Pharmacokinetic factors may thus be partly responsible for the delayed action of the drug in rheumatic conditions. 5. Haemodialysis will not aid in the case of oral overdose with hydroxychloroquine. Although the proportionate increase in clearance may be large, the increase in the fraction of the dose excreted will be negligible. The extensive sequestration of the drug by tissues limits effectiveness of haemodialysis.

How reliable is ESR as a measure of disease activity in rheumatoid arthritis treated with hydroxychloroquine?

Forty-two patients with active rheumatoid arthritis treated with hydroxychloroquine sulphate (400 mg day-1) for six months have been compared with patients treated with D-penicillamine (n = 14), aurothiomalate (n = 13), sulphasalazine (n = 15) and chloroquine (n = 17) to compare the changes in articular index, plasma viscosity and ESR. Results indicate that while articular index and plasma viscosity show significant improvement for all treatments, the ESR fails to improve during hydroxychloroquine therapy.

Biologically-significant scavenging of the myeloperoxidase-derived oxidant hypochlorous acid by some anti-inflammatory drugs

Neutrophils contain the enzyme myeloperoxidase, which oxidizes Cl- ions into the powerful oxidant hypochlorous acid (HOCl). HOCl inactivates alpha 1-antiprotease, permitting uncontrolled protease activities. Most anti-inflammatory drugs tested are capable of reacting with HOCl, but the reactions seem insufficiently rapid under physiological conditions to protect alpha 1-antiprotease against inactivation by HOCl. However, rapid scavenging of HOCl might contribute to the anti-inflammatory effects of penicillamine, gold sodium thiomalate, phenylbutazone and primaquine.

Studies on the mechanism of inhibition of chemotactic tripeptide stimulated human neutrophil polymorphonuclear leucocyte superoxide production by chloroquine and hydroxychloroquine

The effect of chloroquine and hydroxychloroquine on neutrophil superoxide release stimulated by the chemotactic tripeptide N-formyl-methionyl-leucyl-phenylalanine (FMLP) was examined. Both drugs caused time and dose dependent inhibition of superoxide release but had no effect on equilibrium binding of [3H]FMLP to its receptor. Preliminary experiments suggest that these drugs may exert their inhibitory effect on superoxide release by inhibiting the FMLP stimulated hydrolysis of phosphoinositides.