POS0442 RELATIONSHIP BETWEEN PARAOXONASE-1 GENOTYPE, ACTIVITY AND MAJOR ADVERSE CARDIOVASCULAR EVENTS IN PATIENTS WITH RHEUMATOID ARTHRITIS RECEIVING TOFACITINIB

Background:

Paraoxonase-1 (PON1) is a high-density lipoprotein (HDL)-associated enzyme with paraoxonase, lactonase and arylesterase activities.1 PON1 contributes to the antioxidant properties of HDL, and is being investigated for its atheroprotective properties.1 Patients (pts) with rheumatoid arthritis (RA) who are homozygous for the RR genotype of the Q192R gene polymorphism on PON1 (rs662) have increased paraoxonase activity, and lower risk of carotid plaques, vs those with QQ or QR genotypes.2 Tofacitinib is an oral Janus kinase inhibitor for the treatment of RA.

Objectives:

To investigate the relationship between PON1 genotype/activity and risk of major adverse cardiovascular events (MACE) in the tofacitinib RA clinical programme.

Methods:

In this post hoc analysis, data were pooled from pts enrolled in nine Phase 2/3 studies of tofacitinib in RA. Enzyme activities in pt plasma samples were measured at individual study baseline (BL) and at follow-up visits using three substrates: paraoxon (paraoxonase activity), dihydrocoumarin (lactonase activity) and phenylacetate (arylesterase activity). The effect of the PON1 Q192R genotype (QQ, QR or RR) on BL paraoxonase/lactonase/arylesterase activity was assessed using linear regression for each study, with age and sex as covariates, and then fixed-effect meta-analysis assessed effects across studies. The risk of MACE by enzyme activity was determined using Cox proportional hazards regression stratified by clinical studies. Univariate regression against BL enzyme activity and other risk factors, as well as both minimally and fully adjusted multivariable regressions against time-varying enzyme activity, are presented.

Results:

The analysis included 1969 pts with RA who received ≥1 dose of tofacitinib and had PON1 activity measures available at BL; 39 pts had ≥1 MACE event. Compared with the QQ genotype, the RR genotype had a highly significant positive association with BL paraoxonase activity, and a highly significant negative association with BL lactonase and arylesterase activity (Table 1). A univariate analysis identified several BL covariates significantly associated with risk of MACE (Figure 1a). Time-varying models found a highly significant association of increased paraoxonase activity over time with lower risk of future MACE, even after controlling for low-density lipoprotein or HDL cholesterol levels, and other traditional cardiovascular (CV) risk factors identified in univariate analysis (Figure 1b), with similar findings for lactonase and arylesterase (data not shown).

Table 1.

Effect of PON1 genotype (RR vs QQ) on BL enzyme activity

nEstimate95% CIp valueCochran’s Q testParaoxonase12291.0350.93, 1.141<0.00010.209Lactonase1188-0.375-0.505, -0.246<0.00010.025Arylesterase1231-1.016-1.382, -0.649<0.00010.251

Fixed-effects model; estimate >0 favours RR genotype and <0 favours QQ genotype

BL, baseline; CI, confidence interval

Conclusion:

Higher activity of the HDL-associated protein PON1 over time was associated with a significantly reduced risk of future MACE in pts with RA receiving tofacitinib, after controlling for traditional CV risk factors and cholesterol levels. Further investigation of PON1 as a novel functional lipid biomarker to assess CV risk in pts with RA is warranted.

References:

[1]Mackness & Mackness. Gene 2015; 567: 12-21.

[2]Charles-Schoeman et al. Arthritis Rheum 2013; 65: 2765-2772.

Acknowledgements:

Study sponsored by Pfizer Inc. Medical writing support was provided by Jennifer Higginson, CMC Connect, and funded by Pfizer Inc.

Disclosure of Interests:

Christina Charles-Schoeman Consultant of: AbbVie, Gilead, Pfizer Inc, Regeneron-Sanofi, Grant/research support from: AbbVie, Bristol-Myers Squibb, Pfizer Inc, Craig Hyde Shareholder of: Pfizer Inc, Employee of: Pfizer Inc, Shunjie Guan Shareholder of: Pfizer Inc, Employee of: Pfizer Inc, Neil Parikh: None declared, Jennifer Wang: None declared, Ani Shahbazian: None declared, Lori Stockert Shareholder of: Pfizer Inc, Employee of: Pfizer Inc, John Andrews Shareholder of: Pfizer Inc, Employee of: Pfizer Inc

Remodeling of the HDL proteome with treatment response to abatacept or adalimumab in the AMPLE trial of patients with rheumatoid arthritis

BACKGROUND AND AIMS

To evaluate changes in the high-density lipoprotein (HDL) proteome and HDL function in active rheumatoid arthritis (RA) patients initiating therapy with abatacept or adalimumab in the Abatacept Versus Adalimumab Comparison in Biologic-Naïve RA Subjects with Background Methotrexate (AMPLE) study.

METHODS

Ultra high-pressure liquid chromatography (UHPLC) coupled with ion mobility mass spectrometry (LC-IM-MS) was used to analyze proteins associated with immunoaffinity-captured HDL from plasma of 30 patients with RA randomized to either abatacept (n = 15) or adalimumab (n = 15) therapy. Paraoxonase 1 (PON1) activity, HDL anti-oxidant capacity, cholesterol profiles, and homocysteine levels were also measured at baseline and following treatment. Repeated-measures analyses were performed using mixed-effect linear models to model the within-subject covariance over time.

RESULTS

In models controlling for age, sex and treatment group, improvement in inflammation measured by decreases in CRP was associated with improvement in HDL function and changes in several HDL-associated proteins including significant decreases in lipopolysaccharide-binding protein, serum amyloid A-I (SAA-I) and inter-alpha-trypsin inhibitor heavy chain H4 (p values < 0.05). Improvement in disease activity was also associated with changes in multiple HDL-associated proteins. Adalimumab was associated with higher PON1 activity, HDL-associated serotransferrin, and HDL-associated immunoglobulin J chain, and lower HDL-associated SAA-I over time compared with abatacept.

CONCLUSIONS

Improvement in inflammation associated with treatment of RA, using either abatacept or adalimumab in the AMPLE study, was associated with improvement in HDL function and significant alterations in the HDL proteome, including proteins involved in the immune response, proteinase inhibition, and lipid metabolism.

Experimental gastritis in mice enhances anxiety in a gender-related manner

There is a gender-related comorbidity of pain-related and inflammatory bowel diseases with psychiatric diseases. Since the impact of experimental gastrointestinal inflammation on the emotional-affective behavior is little known, we examined whether experimental gastritis modifies anxiety, stress coping and circulating corticosterone in male and female Him:OF1 mice. Gastritis was induced by adding iodoacetamide (0.1%) to the drinking water for at least 7 days. Inflammation was assessed by gastric histology and myeloperoxidase activity, circulating corticosterone determined by enzyme immunoassay, anxiety-related behavior evaluated with the elevated plus maze and stress-induced hyperthermia tests, and depression-like behavior estimated with the tail suspension test. Iodoacetamide-induced gastritis was associated with gastric mucosal surface damage and an increase in gastric myeloperoxidase activity, this increase being significantly larger in female mice than in male mice. The rectal temperature of male mice treated with iodoacetamide was enhanced, whereas that of female mice was diminished. The circulating levels of corticosterone were reduced by 65% in female mice treated with iodoacetamide but did not significantly change in male mice. On the behavioral level, iodoacetamide treatment caused a decrease in nocturnal home-cage activity, drinking and feeding. While depression-related behavior remained unaltered following induction of gastritis, behavioral indices of anxiety were significantly enhanced in female but not male mice. There was no correlation between the estrous cycle and anxiety as well as circulating corticosterone. Radiotracer experiments revealed that iodoacetamide did not readily enter the brain, the blood-brain ratio being 20:1. Collectively, these data show that iodoacetamide treatment causes gastritis in a gender-related manner, its severity being significantly greater in female than in male mice. The induction of gastritis in female mice is associated with a reduction of circulating corticosterone and an enforcement of behavioral indices of anxiety. Gastric inflammation thus has a distinct gender-dependent influence on emotional-affective behavior and its neuroendocrine control.

Endotoxin pretreatment modifies peristalsis and attenuates the antipropulsive action of adrenoceptor agonists in the guinea-pig small intestine

The action of endotoxin to alter gastrointestinal motility in vivo may reflect a direct effect on the gut or result from vascular and other systemic manifestations of this sepsis model. Here we examined whether in vivo pretreatment of guinea-pigs with endotoxin modifies peristalsis in the isolated gut and influences the antipropulsive action of adrenoceptor agonists. Distension-induced peristalsis was recorded in fluid-perfused segments of the small intestine taken from animals pretreated intraperitoneally with endotoxin (1 mg kg(-1)Escherichia coli lipopolysaccharide) or vehicle 4 or 20 h before. Clonidine, adrenaline, noradrenaline, dopamine and dobutamine inhibited peristalsis with differential potency. Endotoxin pretreatment lowered the peristaltic pressure threshold and altered other parameters of baseline peristalsis in a time-related manner. The potency and efficacy of clonidine to inhibit peristalsis were markedly decreased after endotoxin administration, while the potency of the other test drugs was less attenuated. The antipropulsive action of clonidine in control segments was reduced by yohimbine and prazosin, whereas in segments from endotoxin-pretreated animals it was antagonized by yohimbine but not prazosin. We conclude that systemic endotoxin pretreatment of guinea-pigs modifies baseline peristalsis by an action on the gut and inhibits the antipropulsive action of adrenoceptor agonists through changes in adrenoceptor activity.

PACAP-(6-38) inhibits the effects of vasoactive intestinal polypeptide, but not PACAP, on the small intestinal circular muscle

Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating peptide-(1-38) (PACAP) have been found to stimulate distension-induced peristaltic motility in the guinea-pig isolated small intestine. In this study, we tested whether the putative VIP/PACAP receptor antagonist PACAP-(6-38) counteracts the properistaltic effect of VIP and PACAP in isolated segments of the guinea-pig small intestine. VIP (100 nM) and PACAP (30 nM) had a stimulatory effect, i.e., lowered the peristaltic pressure threshold at which peristaltic waves were triggered and enhanced the frequency of peristaltic waves. PACAP-(6-38) (3 microM) was per se without effect on peristalsis but prevented or reversed the peristaltic motor stimulation caused by VIP, when it was given before or after the agonist, respectively. PACAP-(6-38), however, failed to antagonize the properistaltic effect of PACAP. In ileal circular strips treated with tetrodotoxin (1 microM) and indomethacin (3 microM), spontaneous myogenic activity was inhibited by VIP (5-30 nM). This effect was significantly reduced by a pretreatment with PACAP-(6-38) (3 microM). A similar inhibition by PACAP-(1-38) (10-500 nM) was not influenced by the antagonist. It is concluded that PACAP-(6-38) is a VIP receptor antagonist, both in the peristaltic motor pathways and at the level of the circular muscle of the guinea-pig small intestine. The lack of a motor effect of PACAP-(6-38) on its own indicates that VIP acting on PACAP-(6-38)-sensitive receptors (located on neurons and/or the smooth muscle) is unlikely to participate in peristaltic motor regulation.

Regulation of guinea pig intestinal peristalsis by endogenous endothelin acting at ET(B) receptors

BACKGROUND & AIMS

Endothelins are expressed in many enteric neurons of the gut. Because activation of endothelin ET(A) and ET(B) receptors is known to alter intestinal muscle activity, the effect of ET(A) and ET(B) receptor agonists and antagonists on propulsive peristalsis was examined.

METHODS

Repetitive peristalsis in fluid-perfused segments of the guinea pig isolated small intestine was elicited by a rise of the intraluminal pressure and recorded via the pressure changes generated by the peristaltic waves.

RESULTS

Endothelin 1 (0.3-10 nmol/L added to the organ bath) stimulated peristalsis as shown by a decrease in the pressure threshold at which peristaltic waves were triggered, whereas the endothelin analog sarafotoxin 6c (0.3-10 nmol/L) inhibited peristalsis as reflected by an increase in the pressure threshold. The ET(A) receptor antagonist BQ-123 (3 micromol/L) converted the properistaltic action of endothelin 1 to an antiperistaltic action, whereas the ET(B) receptor antagonist BQ-788 (3 micromol/L) prevented the antiperistaltic action of sarafotoxin 6c. BQ-788, but not BQ-123, facilitated peristalsis on its own. Additional experiments indicated that the properistaltic action of endothelin 1 is mediated by enteric neurons, whereas the peristaltic motor effects of sarafotoxin 6c and BQ-788 are caused by a direct action on the muscle.

CONCLUSIONS

ET(A) receptor activation stimulates, whereas ET(B) receptor activation inhibits, intestinal peristalsis. The ability of BQ-788 to facilitate peristalsis per se points to a physiologic role of ET(B) receptors in peristaltic motor regulation.

Differences in circular muscle contraction and peristaltic motor inhibition caused by tachykinin NK1 receptor agonists in the guinea-pig small intestine

The tachykinin NK1 receptor agonist substance P methyl ester (SPOME) impedes intestinal peristalsis by releasing nitric oxide (NO) from inhibitory motor neurones. Since NK1 receptor agonists differ in their receptor interaction, we set out to compare a range of NK1 receptor agonists including SPOME, septide and GR-73 632 in their effects on propulsive peristalsis and circular muscle activity in the guinea-pig isolated small intestine. SPOME (100-300 nM) inhibited peristalsis by a rise of the pressure threshold at which peristaltic waves were triggered, whereas septide and GR-73 632 (30-300 nM) interrupted peristalsis by causing circular muscle spasms. Separate experiments showed that all three NK1 receptor agonists caused contraction of the circular muscle, which was enhanced by the NO synthase inhibitor NG-nitro-L-arginine methyl ester (300 mM) and the P2X purinoceptor antagonist suramin (300 mM). In contrast, tetrodotoxin (300 nM) augmented the contractile effect of septide and GR-73 632 but not that of SPOME. It is concluded that the motor response to NK1 receptor agonists involves release of NO and adenosine triphosphate from inhibitory motor neurones. However, the NK1 receptor agonists differ in the mechanism by which they cause inhibitory transmitter release, which corresponds to differences in their antiperistaltic action.

Cannabinoid inhibition of guinea-pig intestinal peristalsis via inhibition of excitatory and activation of inhibitory neural pathways

Since activation of cannabinoid CB1 receptors inhibits gastrointestinal transit in the mouse, this study analyzed the action of the cannabinoid receptor agonist methanandamide on distension-induced propulsive motility. Peristalsis in luminally perfused segments of the guinea-pig isolated ileum was elicited by a rise of the intraluminal pressure. The pressure threshold at which peristaltic contractions were triggered was used to quantify drug effects. Methanandamide (0.1-3 microM) inhibited peristalsis as deduced from a concentration-related increase in the peristaltic pressure threshold, an action that was prevented by the CB1 receptor antagonist SR141716A (1 microM) per se, which had no effect on peristalsis. The distension-induced ascending reflex contraction of the circular muscle was likewise depressed by methanandamide in a SR141716A-sensitive manner, whereas indomethacin-induced phasic contractions of the circular muscle were left unchanged by methanandamide. The anti-peristaltic action of methanandamide was inhibited by apamin (0.5 microM), attenuated by N-nitro-L-arginine methyl ester (300 microM) and left unaltered by suramin (300 microM), pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (150 microM) and naloxone (0.5 microM). It is concluded that methanandamide depresses intestinal peristalsis via activation of CB1 receptors on enteric neurons, which results in blockade of excitatory motor pathways and facilitation of inhibitory pathways operating via apamin-sensitive K+ channels and nitric oxide.

Effects of bombesin on the canine gallbladder motility: in vivo and in vitro experiments

The effects of bombesin (BM) on the canine gallbladder motility was studied under two different experimental conditions: (i) in conscious dogs with a balloon chronically implanted into the gallbladder lumen where intragallbladder pressure was recorded in mm Hg by means of a pressure transducer, and (ii) in smooth muscle preparations isolated from different regions of the gallbladder where the contractions were recorded isometrically by means of mechanoelectrical transducers. Similar to CCK8 bolus injection of. BM i.v. increased the gallbladder pressure in a dose-dependent manner. The response was characterized by a slow increase of the tone and a gradual restoration (in 4 to 8 min) of the background activity. The threshold dose and the maximum dose were 30 ng/kg and 100 ng/kg for BM and 1 ng/kg and 10 ng/kg for CCK8, respectively. Both atropin (10 to 50 micrograms/kg) and hexamethonium (0.5 to 3 mg/kg) injected i.v. 5 to 10 min before BM strongly reduced or even abolished the gallbladder response to BM. Somatostatin (1 to 2 micrograms/kg) and VIP (0.5 to 1 microgram/kg) injected 3 to 5 min before BM also exerted a strong inhibitory effect on the canine gallbladder response to BM. However BM (up to 10(-6) M) had no effect on the spontaneous or electrically-induced contractions of the canine gallbladder smooth muscle preparations. The results suggest the involvement of prejunctional cholinergic-, somatostatinergic- and VIP-ergic pathways in the bombesin-induced increase of the gallbladder pressure of conscious dogs.

Interactions between histaminergic and cholinergic pathways of gastric motility regulation

Smooth muscle preparations, isolated in a circular direction from guinea pig gastric fundus, were used to study the effects of H1 and H2 antagonists on acetylcholine (ACH)- and histamine (HA)-induced contractions as well as the effects of HA antagonists on spontaneous contractile activity. HA (1 x 10(-9) M to 1 x 10(-5) M) concentration-dependently enhanced the tone of the strips with ED50 = 3.5 x 10(-7) M. Applied 5 min before HA, the H1 antagonists (mepyramine, diphenhydramine, dimethpyrindene) and the H2 blockers (ranitidine, cimetidine, roxatidine) reduced HA-induced contractions. HA in concentrations of 1 x 10(-8) M to 1 x 10(-7) potentiated, and in higher concentrations (1 x 10(-6) M to 1 x 10(-5) M) inhibited, smooth muscle contractions evoked by low frequency electrical field stimulation (EFS). The H1 blockers (1 x 10(-6) M to 1 x 10(-4) M) concentration-dependently enhanced smooth muscle tone, the maximum contractions being about 50% smaller than the contractile responses to 1 x 10(-5) M ACH and 5 x 10(-5) M HA. Tetrodotoxin, atropine and indomethacin shifted to the right the concentration-response curve for mepyramine, reducing its maximum by 25, 58 and 62%, respectively. The H2 blocker ranitidine also suppressed (by 42%) mepyramine-evoked increase in the fundic strips tone. The H1 antagonists reduced ACH-induced contractions of the smooth muscle strips and did not affect the contractions in response to EFS. The H2 blockers had no effect on tone and ACH-evoked contractions of the smooth muscle strips but concentration-dependently enhanced both the contractions and [3H]-ACH release in response to EFS. The results demonstrate the presence of both H1 and H2 postsynaptic receptors which are involved in the direct myogenic action of HA on guinea pig gastric fundus smooth muscles. It also appears that HA might concentration-dependently modulate the cholinergic neurotransmission in gastric fundus. It could be suggested that H1 blockers have a direct myogenic effect on guinea pig gastric fundus smooth muscle and might also interact postsynaptically with muscarinic receptors in this tissue.

Different effects of H1 and H2 blockers on the tone and the contractile activity of guinea pig stomach fundus

The action of H1 and H2 blockers on the spontaneous and evoked contractile activity of gastric fundus smooth muscles as well as the effects of H2 antagonists on the release of acetylcholine (ACh) from gastric myenteric neurons were studied. The experiments were performed on smooth muscle strips (25 x 3 mm) cut out in circular direction from guinea pig fundus region. In concentrations of 1 x 10(-7) M to 1 x 10(-4) M, the H1 blockers diphenhydramine (DPH), mepyramine (MEP) and dimethpyrindene (DMPD), but not the H2 blockers ranitidine (RAN), cimetidine (CIM) and roxatidine (ROX), increased in a concentration-dependent manner the smooth muscle tone, the maximum contractions being about 50% of the contractile effects of 1 x 10(-5) M ACH and 5 x 10(-5) M histamine (HA). The concentration-dependent contractions of the stomach fundus strips in response to electrical field stimulation (EFS) were enhanced by RAN, CIM and ROX (but not by MEP and DPH), all in concentrations of 1 x 10(-7) M to 1 x 10(-4) M. EFS increased the resting [3H]-ACh release by 67.8%, the S2/S1 ratio being 0.85 +/- 0.04. ROX in a concentration of 1 x 10(-5) M significantly increased (by 16.1%) the EFS-induced release with a S2/S1 ratio of 1.22 +/- 0.04. The ROX effect on the [3H]-ACh release was reduced or even abolished by 1 x 10(-6) M tetrodotoxin (TTX) and 1 x 10(-6) M scopolamine or in Ca(2+)-free medium, while 1 x 10(-6) M hexamethonium did not change it. It might be concluded that H2 blockers have no direct myogenic effect and do not interfere with muscarinic receptors in guinea pig stomach fundus. The H2 antagonists enhance the EFS-evoked contractions of the gastric smooth muscle most probably by increasing the release of ACH.