Serum sCD40L levels are increased in patients with psoriatic arthritis and are associated with clinical response to apremilast.

The pathogenesis of psoriatic arthritis (PsA) involves several pathways, including the CD40/CD40L signaling which promotes the release of multiple cytokines. Transmembrane CD40L is also released in soluble form (sCD40L) and phosphodiesterase 4 (PDE4) seems to be involved in its cleavage. We aimed to investigate whether apremilast, a PDE4 inhibitor, could modify circulating levels of sCD40L in PsA patients, and the possible associations of these changes with clinical response. Consecutive PsA patients starting apremilast in routine clinical practice were prospectively observed. Disease Activity of Psoriatic Arthritis (DAPSA), Psoriasis Area Severity Index (PASI), Leeds Enthesitis Score (LEI) and serum samples were collected at baseline and at 6 months. Samples were run in a Bio-Plex ProTM plate for sCD40L. To investigate the association of sCD40L level with DAPSA based minor response, low disease activity (LDA) and/or remission at 6 months of treatment, multivariate logistic regression models with backward selection (P < 0·05) were built. We studied 27 patients (16 of 27 women, 59·6%) with PsA and mean age [± standard deviation (s.d.)] of 58·4 ± 10 years. A significant reduction of the mean values of DAPSA, LEI and PASI was detected at 6 months. Mean serum levels of sCD40L decreased from baseline 5364 ± 2025 pg/ml to 4412 ± 2629 at 6 months (P = 0·01). Baseline DAPSA [odds ratio (OR) = 0·80, 95% confidence interval (CI) = 0·65-0·98] and sCD40L (OR = 1·001, 95% CI = 1·0001-1·0027) were independently associated with DAPSA LDA/remission at 6 months. In PsA patients, sCD40L levels decrease upon apremilast treatment and might predict short-term clinical response to apremilast.

Correlation between serum levels of IL-15 and IL-17 in patients with idiopathic inflammatory myopathies.

OBJECTIVES: To assess the serum levels of interleukin (IL)-15 and IL-17 in patients with idiopathic inflammatory myopathies (IIM) and correlate them with levels of IL-1 receptor antagonist (IL-1ra), IL-6, IL-10, interferon (IFN)-γ, monocyte chemoattractant protein (MCP)-1, macrophage inflammatory protein (MIP)-1α, and MIP-1ß. Possible correlations with disease activity parameters were also evaluated. METHOD: Sera from 14 patients with new-onset polymyositis (PM), 10 with dermatomyositis (DM), seven with anti-synthetase syndrome (ASS) and 19 healthy controls (HC) were analysed by multiplex immunoassay. Sera from 19 patients were analysed after a median follow-up of 5 months. All patients underwent physical examination, manual muscle testing (MMT) using the five-point MMT scales, the Health Assessment Questionnaire (HAQ), and serum creatine kinase (CK) measurement. All patients received glucocorticoids, and 13 were taking immunosuppressive therapy. RESULTS: At baseline, serum levels of IL-15, IL-17, MCP-1, and MIP-1ß were significantly higher in IIM patients than in HC. IL-17 serum levels were directly correlated (r = 0.39, p = 0.02) with disease duration while a significant inverse correlation was detected between IL-17 levels and MMT scores (r = -0.4, p = 0.02). The highest IL-15 levels were present in DM patients (p = 0.02 vs. PM). The most striking finding was the strong correlation between IL-15 and IL-17 levels (r = 0.60, p = 0.0001), and this correlation was even stronger in DM patients (r = 0.82, p = 0.006). CONCLUSIONS: The strong correlation between IL-15 and IL-17 in IIM patients, and especially in DM, suggests that there may be an interplay between the two cytokines in the pathogenesis of myositis. Further studies of larger patient cohorts and of muscle biopsies are needed to confirm these preliminary data.

Possible interplay between interleukin-15 and interleukin-17 into the pathogenesis of idiopathic inflammatory myopathies.

The aim of this study was to assess the serum levels of interleukin (IL)-15 and IL-17 in patients with idiopathic inflammatory myopathies (IIM) and correlate them with IL-6, IL-10, monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-1α (MIP-1α), MIP-1ß levels. Possible correlations with disease activity parameters were also evaluated. Sera from 14 polymyositis (PM), 10 dermatomyositis (DM), 7 anti-synthetase syndrome new onset patients and 19 healthy controls (HCs) were analyzed by multiplex immunoassay. Sera from 19 patients were analyzed after 5 months median follow-up. All patients underwent physical examination, the 5-points manual muscle test (MMT), the health assessment questionnaire and serum creatine kinase measurement. All patients received glucocorticoids, and 13 were taking also immunosuppressive therapy. At baseline, serum levels of IL-15, IL-17, MCP-1 and MIP-1ß were significantly higher in IIM patients than in HCs. IL-17 serum levels were directly correlated with disease duration (r=0.39, P=0.02), while a significant inverse correlation was detected between IL-17 levels and MMT scores (r=-0.4, P=0.02). The highest IL-15 levels were present in DM patients (P=0.02 vs PM). The most striking finding was the strong correlation between IL-15 and IL-17 levels (r=0.60, P=0.0001), and this correlation was even stronger in DM patients (r=0.82, P=0.006). The strong correlation between IL-15 and IL-17 in IIM patients, and especially in DM, suggests that there may be a interplay between the two cytokines in the pathogenesis of myositis. Further studies of larger patient cohorts and muscle biopsies are needed to confirm these preliminary data.

The mitochondrial oxoglutarate carrier: cysteine-scanning mutagenesis of transmembrane domain IV and sensitivity of Cys mutants to sulfhydryl reagents.

Using a functional mitochondrial oxoglutarate carrier mutant devoid of Cys residues (C-less carrier), each amino acid residue in transmembrane domain IV and flanking hydrophilic loops (from T179 to S205) was replaced individually with Cys. The great majority of the 27 mutants exhibited significant oxoglutarate transport in reconstituted liposomes as compared to the activity of the C-less carrier. In contrast, Cys substitution for G183, R190, Q198, and Y202, in either C-less or wild-type carriers, yielded molecules with complete loss of oxoglutarate transport activity. G183 and R190 could be partially replaced only by Ala and Lys, respectively, whereas Q198 and Y202 were irreplaceable with respect to oxoglutarate transport. Of the single-Cys mutants tested, only T187C, A191C, V194C, and N195C were strongly inactivated by N-ethylmaleimide and by low concentrations of methanethiosulfonate derivatives. Oxoglutarate protects Cys residues at positions 187, 191, and 194 against reaction with N-ethylmaleimide. These positions as well as the residues found to be essential for the carrier activity, except Y202 which is located in the extramembrane loop IV-V, reside on the same face of transmembrane helix IV, probably lining part of a water-accessible crevice or channel between helices of the oxoglutarate carrier.

Inactivation of the reconstituted oxoglutarate carrier from bovine heart mitochondria by pyridoxal 5'-phosphate.

The effect of pyridoxal 5'-phosphate and some other lysine reagents on the purified, reconstituted mitochondrial oxoglutarate transport protein has been investigated. The inhibition of oxoglutarate/oxoglutarate exchange by pyridoxal 5'-phosphate can be reversed by passing the proteoliposomes through a Sephadex column but the reduction of the Schiff's base by sodium borohydride yielded an irreversible inactivation of the oxoglutarate carrier protein. Pyridoxal 5'-phosphate, which caused a time- and concentration-dependent inactivation of oxoglutarate transport with an IC50 of 0.5 mM, competed with the substrate for binding to the oxoglutarate carrier (Ki = 0.4 mM). Kinetic analysis of oxoglutarate transport inhibition by pyridoxal 5'-phosphate indicated that modification of a single amino acid residue/carrier molecule was sufficient for complete inhibition of oxoglutarate transport. After reduction with sodium borohydride [3H]pyridoxal 5'-phosphate bound covalently to the oxoglutarate carrier. Incubation of the proteoliposomes with oxoglutarate or L-malate protected the carrier against inactivation and no radioactivity was found associated with the carrier protein. In contrast, glutarate and substrates of other mitochondrial carrier proteins were unable to protect the carrier. Mersalyl, which is a known sulfhydryl reagent, also failed to protect the oxoglutarate carrier against inhibition by pyridoxal 5'-phosphate. These results indicate that pyridoxal 5'-phosphate interacts with the oxoglutarate carrier at a site(s) (i.e., a lysine residue(s) and/or the amino-terminal glycine residue) which is essential for substrate translocation and may be localized at or near the substrate-binding site.

Inhibition of the reconstituted mitochondrial oxoglutarate carrier by arginine-specific reagents.

The effect of arginine-specific reagents on the function of the purified and reconstituted oxoglutarate carrier protein of the inner mitochondrial membrane has been investigated. The alpha-dicarbonyl reagents 2,3-butanedione, 2,3-pentanedione, 2,3- and 3,4-hexanedione, 1-phenyl-1,2-propanedione, phenylglyoxal, and phenylglyoxal derivatives caused a concentration-dependent inhibition of oxoglutarate transport with an IC50 of 0.05 mM for 2,3-hexanedione, 0.08 mM for 4-hydroxy-3-nitrophenylglyoxal, and 0.17 mM for 2,3-pentanedione. The inhibition increased with pH from 6.0 to 8.0, indicating that the pK of the reacting group(s) is rather high. Mersalyl and pyridoxal 5'-phosphate (or 4,4'-dinitrostilbene-2,2'-disulfonate), which are known to react specifically and reversibly with cysteine residues and lysine residues, respectively, were unable to protect the oxoglutarate carrier against inhibition by alpha-dicarbonyl reagents. Other diketone compounds, which do not react with arginine residues, had no significant effect on the oxoglutarate transport activity. Oxoglutarate and L-malate effectively protected the oxoglutarate carrier against inactivation caused by arginine-specific reagents; other dicarboxylates, which are not substrates of the carrier, had no protective effect. A 50% substrate protection was observed at half-saturation of the external binding site. These results indicate that the arginine-specific reagents used in this investigation interact with the oxoglutarate carrier at the level of an arginine residue(s), which is essential for binding and/or translocation of substrates and which may be localized in, or near, the substrate-binding site.

Photoaffinity labeling of the mitochondrial oxoglutarate carrier by azido-phthalonate.

The effect of azido-phthalonate, a photoreactive analogue of oxoglutarate, on the transport of oxoglutarate was investigated in proteoliposomes reconstituted with the purified oxoglutarate carrier. In the dark, azido-phthalonate inhibits the reconstituted oxoglutarate/oxoglutarate exchange in a competitive manner with a Ki of 0.38 mM. Upon photoirradiation, the inhibition of the oxoglutarate exchange by azido-phthalonate is not removed by passing the proteoliposomes through a Sephadex column. The light-induced inhibition of the oxoglutarate/oxoglutarate exchange activity by azido-phthalonate is time- and concentration-dependent. The kinetic analysis of transport inhibition by azido-phthalonate reveals that one molecule of this substrate analogue bound to the functional carrier molecule is responsible for complete inhibition of the carrier function. Azido-[3H]phthalonate binds to the oxoglutarate carrier covalently. Incubation of the proteoliposomes with oxoglutarate during photoirradiation in the presence of azido-phthalonate protects the carrier against inactivation and decreases the amount of radioactivity which is found to be associated with the carrier protein. It is concluded that azido-phthalonate can be used for photoaffinity labeling of the mitochondrial oxoglutarate carrier at the substrate-binding site.

myo-inositol transport in rat intestinal brush border membrane vesicles, and its inhibition by D-glucose.

The uptake of myo-inositol into rat intestinal brush border membrane vesicles (BBMV) has been investigated. It is demonstrated that myo-inositol is transported into the vesicles by a secondary active process, specifically using the sodium gradient as the driving force. In the absence of sodium gradient, the transport reaction is still sodium dependent, and rheogenic, indicating that a myo-inositol/sodium cotransport is likely to occur. A kinetic analysis shows an hyperbolic saturation process with a Km of 0.16 +/- 0.02 mM with respect to myo-inositol and Vmax of 68.5 +/- 21.2 pmol/min per mg protein. The transport is inhibited by D-glucose, phloridzin and few other sugars. The mechanism of D-glucose inhibition appears to be of the mixed type. Finally, the myo-inositol transport is trans-activated by myo-inositol itself, but not by D-glucose. It is concluded that myo-inositol is transported into rat intestine BBMV by a specific transport system, which is also able to bind D-glucose, but not efficiently transport it across the membrane.