POS0695 EFFECT OF METHOTREXATE AND FOLIC ACID CO-ADMINISTRATION IN ARTHRITIS

Background

Methotrexate (MTX) is the recommended first-line treatment for rheumatoid arthritis. Adjuvant-induced arthritis (AIA) rat is a robust model with a high prevalence of arthritis used to investigate arthritis. MTX reduces inflammation, but associated with adverse events, such as gastrointestinal, hepatic, and hematology toxicity (1). To reduce these side effects, folic acid (FA) is administrated at distance to MTX with no defined recommendation for its dosing (5-25mg/week) or time point of administration (2) (1-3 days after MTX application). Whether the complicated therapeutic regimen with MTX once a week and FA at another time point affects compliance is an open question. MTX is metabolized in polyglutamates derivates (MTX-PG), which is a biomarker of MTX efficacy as its half-life (1-4 weeks) is longer than MTX (4h) (3).

Objectives

The aim of this study was to assess efficacy and tolerance of co-administration of MTX and FA compared to MTX with FA applied one day after MTX in the AIA.

Methods

Female Lewis rat were randomly divided in three groups and received an injection of Mycobacterium butyricum defining day (D) 0 to induce arthritis. An historic AIA group was used as control. Treatment began on D9, one day before arthritis onset in this model. The first group rats were treated with MTX only (n=13), the second group received MTX and FA at the same day (n=14), and the third group received FA one day after MTX administration (n=14). MTX was administrated intraperitoneally (IP) at 1 mg/kg every 3 days (4) and FA was delivered IP at 0.17 mg/kg. Arthritic index (AI) and ankle circumference (AC) were monitored to assess arthritis. Microcomputed tomography of the ankle was performed to assess bone loss. Moreover, complete blood count, transaminases, and MTX-PG were assessed.

Results

Arthritis developed at D10 in all groups. AI and AC were similar in MTX groups at the various time points. At D17, arthritis severity was lower in MTX groups (AI (mean and standard deviation): 1.4 ± 1.6; AC: 35 ± 7 mm) compared to AIA historical group (AI: 3.3 ± 0.6; AC: 42 ± 4 mm). Bone erosion and bone loss parameters were similar in all groups. Cortical porosity was around 0.40% ± 0.15 and bone volume / total volume was around 0.22% ± 0.13. MTX-PG1 was found at similar levels in MTX groups and correlated negatively with AI in MTX alone or MTX and FA at the same day groups (p<0.05 and p<0.01, respectively). Finally, white and red blood cells, platelets, hemoglobin, mean corpuscular volume, transaminases, and creatinine were found at a similar level in MTX groups.

Conclusion

Co-administration of MTX with FA on the same day is effective compared to FA application one day after MTX. MTX metabolism was not affected, as demonstrated by the MTX-PG concentrations. The biological tolerance between the protocols was comparable. Thus, co-administration of MTX and FA seems to be possible and may be more convenient to the patients and improve compliance at the end.

References

[1]Albrecht K, Müller-Ladner U. Side effects and management of side effects of methotrexate in rheumatoid arthritis. Clin Exp Rheumatol 2010;28:S95-101.

[2]Gaujoux-Viala C, et al. Recommendations of the French Society for Rheumatology for managing rheumatoid arthritis. Joint Bone Spine 2014;81:287–297.

[3]Angelis-Stoforidis P, et al. Methotrexate polyglutamate levels in circulating erythrocytes and polymorphs correlate with clinical efficacy in rheumatoid arthritis. Clin Exp Rheumatol 1999;17:313–320.

[4]Le Goff B, et al. A combination of methotrexate and zoledronic acid prevents bone erosions and systemic bone mass loss in collagen induced arthritis. Arthritis Res Ther 2009;11:R185.

Acknowledgements

We thank Ghislaine Roux, Diane Denis and Valentine Berrucas for their support in animal experiments. We thank Xavier Delavenne for MTX-PG dosage. We thank Nadia Boutahar for transaminases and creatinine dosage.

Disclosure of Interests

Elisa Dalix Grant/research support from: GEBRO, Mathieu Maalouf Grant/research support from: GEBRO, Sylvie Peyroche Grant/research support from: GEBRO, Arnaud Vanden-Bossche Grant/research support from: GEBRO, Charles-Antoine Arthaud Grant/research support from: GEBRO, Sophie Hodin Grant/research support from: GEBRO, Hubert MAROTTE Grant/research support from: GEBRO, Nordic Pharma, Rüdiger Müller Grant/research support from: GEBRO, Nordic Pharma

Evidence for homeostatic adjustments of rat somatosensory cortical neurons to changes in extracellular acetylcholine concentrations produced by iontophoretic administration of acetylcholine and by systemic diisopropylfluorophosphate treatment

We describe the responses of single units in the awake (24 cells) or urethane-anesthetized (37 cells) rat somatosensory cortex during repeated iontophoretic pulses (1.0 s, 85 nA) of acetylcholine, both before and after systemic treatment with the irreversible acetylcholinesterase inhibitor diisopropylfluorophosphate (i.p., 0.3-0.5 LD50). The time-course of the response to acetylcholine pulses differed among cortical neurons but was characteristic for a given cell. Different time-courses included monophasic excitatory or inhibitory responses, biphasic (excitatory-inhibitory, inhibitory-excitatory, excitatory-excitatory, and inhibitory-inhibitory), and triphasic (excitatory-excitatory-inhibitory, inhibitory-inhibitory-excitatory, and inhibitory-excitatory-inhibitory) responses. Although the sign and time-course of the individual responses remained consistent, their magnitude fluctuated across time; most cells exhibited either an initial increase or decrease in response magnitude followed by oscillations in magnitude that diminished with time, gradually approaching the original size. The time-course of the characteristic response to an acetylcholine pulse appeared to determine direction and rate of change in response magnitude with successive pulses of acetylcholine. Diisopropylfluorophosphate treatment, given 1 h after beginning repeated acetylcholine pulses, often resulted in a gradual increase in spontaneous activity to a slightly higher but stable level. Superimposed on this change in background activity, the oscillations in the response amplitude reappeared and then subsided in a pattern similar to the decay seen prior to diisopropylfluorophosphate treatment. Our results suggest that dynamic, homeostatic mechanisms control neuronal excitability by adjusting the balance between excitatory and inhibitory influences within the cortical circuitry and that these mechanisms are engaged by prolonged increases in extracellular acetylcholine levels caused by repeated pulses of acetylcholine and by acetylcholinesterase inhibition. However, this ability of neurons in the cortical neuronal network to rapidly adjust to changes in extracellular levels of acetylcholine questions the potential efficacy of therapeutic treatments designed to increase ambient levels of acetylcholine as a treatment for Alzheimer's disease or to enhance mechanisms of learning and memory.

Blockade of cholinergic receptors in rat barrel cortex prevents long-term changes in the evoked potential during sensory preconditioning

We offer evidence that acetylcholine (ACh) is involved in the emergence of functional neuronal plasticity induced by whisker pairing. Evoked potentials were recorded within the barrel cortex of awake, adult rats before, during, and after one of five paradigms. In the pairing procedure, each of 50 deflections of a whisker (S1) was followed 150 ms later by the deflection of a second whisker (S2). The explicitly unpaired control procedure differed by the lack of contiguity and contingency between the stimulation of S1 and S2. In the three remaining groups, pairing was performed 30 min after an intraperitoneal injection of either 0.5 ml of saline (150 mM NaCl), 100 mg/kg of atropine methyl nitrate (0.5 ml of AMN in saline), or 100 mg/kg of atropine sulfate (0.5 ml of ATS in saline). Changes in responsiveness to S1 were compared with, and adjusted by, changes in responsiveness to stimulation of S2. Changes in potentials evoked by S1 were interpreted as a change in neuronal excitability occurring when the first innocuous stimulus systematically predicted the appearance of the second innocuous stimulus. When whisker pairing was performed alone or in the presence of either saline or AMN (a blocker of muscarinic cholinoreceptors that does not cross the blood-brain barrier, BBB), responses to S1 increased, whereas, in the presence of ATS (blocker of muscarinic cholinoreceptors that does cross the BBB) or following the explicitly unpaired control, they decreased. The effects of saline, AMN, and ATS on the evoked potential without vibrissae pairing were opposite to those observed when these substances were injected and pairing occurred. Analysis of the behavioral state of the animal showed that the changes observed in the evoked potential could not be attributed to changes in behavioral state. The changes in responsiveness to S1 induced by whisker pairing were independent of neuronal excitability, did not occur in the absence of contingency and contiguity between S1 and S2, were blocked by the muscarinic receptor antagonist ATS, but not by blockade of muscarinic modulation of normal synaptic transmission. Thus activation of muscarinic cholinoreceptors within the CNS were a necessary condition for this form of neuronal plasticity.

Effects of D-AP5 and NMDA microiontophoresis on associative learning in the barrel cortex of awake rats

Experiments involving single-unit recordings and microiontophoresis were carried out in the barrel cortex of awake, adult rats subjected to whisker pairing, an associative learning paradigm where deflections of the recorded neuron's principle vibrissa (S2) are repeatedly paired with those of a non-adjacent one (S1). Whisker pairing with a 300 ms interstimulus interval was applied to 61 cells. In 23 cases, there was no other manipulation whereas in the remaining 38, pairing occurred in the presence of one of three pharmacological agents previously shown to modulate learning, receptive field plasticity and long-term potentiation: N-methyl-D-aspartic acid (NMDA) (n=8), the NMDA receptor antagonist AP5 (n=17) or the nitric oxide synthase inhibitor L-nitro-arginine-N-methyl-ester (L-NAME) (n=13). Non-associative (unpaired) experiments (n=14) and delivery of pharmacological agents without pairing (n=14) served as controls. Changes in neuronal responsiveness to S1 following one of these procedures were calculated and adjusted relative to changes in the responses to S2. On average, whisker pairing alone yielded a 7% increase in the responses to S1. This enhancement differed significantly from the 17% decrease obtained in the non-associative control condition and could not be attributed to variations in the state of the animals because analysis of the cervical and facial muscle electromyograms revealed that periods of increased muscular activity, reflecting heightened arousal, were infrequent (less than 4% of a complete experiment on average) and occurred randomly. The enhancement of the responses to S1 was further increased when whisker pairing was performed in the presence of L-NAME (27%) or NMDA (35%) whereas AP5 reduced it to 1%. During the delivery period, NMDA enhanced both neuronal excitability and responsiveness to S1 whereas AP5 depressed them. However, the effects of both substances disappeared immediately after administration had ended. L-NAME did not affect the level of ongoing activity and responses to S1 significantly. From these data, we concluded that, since the changes in the responses to S1 lasted longer than the periods of both whisker pairing and drug delivery, they were not residual excitatory or inhibitory drug effects on neuronal excitability. Thus, our results indicate that, relative to the unpaired controls, whisker pairing led to a 24% increase in the responsiveness of barrel cortex neurons to peripheral stimulation and that these changes were modulated by the local application of pharmacological agents that act upon NMDA receptors and pathways involving nitric oxide. We can infer that somatosensory cerebral cortex is one site where plasticity emerges following whisker pairing.

A novel actin cDNA is expressed in the neurons of Aplysia californica

A novel actin cDNA has been isolated from an abdominal ganglion cDNA library of Aplysia californica by differential screening. This cDNA of 1596 nucleotides in length encodes a putative actin protein of 41.8 kDa. This protein shows 95.2% identity with another Aplysia actin gene previously shown to be expressed in the muscular sheath of the ganglion (DesGroseillers et al. (1990) Nucleic Acids Res. 18, 3654). However, the 5' and 3' untranslated regions of these cDNAs are completely different. PCR experiments performed with mRNA isolated from dissected neurons, ovotestis or kidney reveal that the gene is expressed in the neurons of the ganglia and in other tissues as well. Southern blot analysis reveals that the neuronal actin gene is a member of a large gene family.