Could we suspect pulmonary veno-oclussive disease with a cardiopulmonary exercise test?

Background

Cardiopulmonary exercise test (CPET) provides information about the pathophysiology of the exercise limitation. CPET parameters in pulmonary arterial hypertension (PAH) exhibit distinctive features, such as low peak oxygen uptake (pVO2), low end tidal carbon dioxide tension (PetCO2) and high ventilation-carbon dioxide slope (VE/VCO2).Pulmonary veno-oclussive disease (PVOD) is a PAH subgroup with particular underlying physiology, difficult diagnosis and poor prognosis.

Purpose

We hypothesized that different CPET patterns could be identified in PAH subgroups, and this may contribute to their diagnosis workup.

Methods

CPETs performed on the following PAH subgroups between September 2019 and January 2020 were prospectively included: Idiopathic PAH (IPAH), Heritable PAH (HPAH), and PAH responders to calcium channel blockers (CCB-R). Due to its low prevalence and its clinical relevance, CPET data on PVOD patients was retrospectively included.

Results

57 CPET were included: 20 IPAH (35%); 13 HPAH (22.8%); 9 CCB-R (15.8%),15 PVOD (26.3%). All patients presented impaired functional capacity with reduced peakVO2 and increased VE/VCO2). Remarkably, PVOD patients,in spite of a younger age, exhibit the worst functional capacity and ventilatory efficiency even showing downward PetCO2 kinetics. CCB-R group achieved the highest peakVO2 and had better ventilatory parameters.(Table 1)

Conclusion

CPET is a useful tool to classify patients by PAH subgroups. Very low PetCO2 at rest and a downward PetCO2 kinetic strongly suggest PVOD, which has significant implications on treatment.

Funding Acknowledgement

Type of funding source: None

Directional translocation resistance of Zika xrRNA

xrRNAs from flaviviruses survive in host cells because of their exceptional dichotomic response to the unfolding action of different enzymes. They can be unwound, and hence copied, by replicases, and yet can resist degradation by exonucleases. How the same stretch of xrRNA can encode such diverse responses is an open question. Here, by using atomistic models and translocation simulations, we uncover an elaborate and directional mechanism for how stress propagates when the two xrRNA ends, [Formula: see text] and [Formula: see text], are driven through a pore. Pulling the [Formula: see text] end, as done by replicases, elicits a progressive unfolding; pulling the [Formula: see text] end, as done by exonucleases, triggers a counterintuitive molecular tightening. Thus, in what appears to be a remarkable instance of intra-molecular tensegrity, the very pulling of the [Formula: see text] end is what boosts resistance to translocation and consequently to degradation. The uncovered mechanistic principle might be co-opted to design molecular meta-materials.

THU0524 FACTORS EXPLAINING PATIENT PERSPECTIVE IN PSORIASIS AND PSORIATIC ARTHRITIS (PSA): THE ROLE OF INFLAMMATION AND STRUCTURAL DAMAGE DETECTED BY ULTRASOUND (THE ECHOPRO STUDY)

Background:

Patient reported outcomes (PROs) reflect patients’ opinion on disease activity, impact of disease, quality of life (QoL) and are essential in the assessment of PsA patients. PROs may be influenced by several factors other than disease activity and severity. Ultrasound (US) is an objective tool to evaluate joint inflammation and structural damage in PsA.

Objectives:

This cross-sectional study aimed at evaluating the role of US-detected inflammation (synovitis, tenosynovitis, enthesitis) and structural damage (erosions, enthesophytes, osteophytes, cortical irregularities), to explain PROs in PsA and to compare that to psoriasis (PsO) patients with and without musculoskeletal (MSK) symptoms.

Methods:

PsA (CASPAR criteria) [1], PsO with MSK symptoms without fulfilling CASPAR criteria (symptoPsO) and PsO with no MSK symptoms (asymptoPsO) were included. Socio-demographic characteristics, comorbidities, disease duration and treatment were collected. All patients underwent to: a) dermatological and rheumatologic assessment: PsO severity, swollen joint count (SJC), tender JC (TJC), number of dactylitis and enthesitis; b) US evaluation of joints, tendons and entheses according to OMERACT definitions[2], (figure 1); c) PROs assessement: fatigue, disability (HAQ) and QoL (SF36). Variables were compared across groups (chi square or one-way ANOVA test). Correlations were evaluated using Spearman’s test.

Results:

208 patients (76 PsA, 64 symptoPsO and 68 asymptoPsO) with similar socio-demographic characteristics and PsO duration were included (table 1). Except for enthesophytes, all US changes were significantly higher in PsA, followed by symptoPsO patients.

Table 1.

Characteristics of the patients:

PsAN= 76SymptoPsON=64AsymptoPsON=68pFemales, N (%)33 (43.4)39 (55.7)23 (37.1)NSAge55.58 ± 12.7152.16 ± 15.6150.03 ± 14.66NSPsoriasis duration18.76 ± 13.3719.47 ± 15.9815.03 ± 12.29NSPASI0 (0; 36)3 (0; 16)5.5 (0; 22.1)<0.00168 TJC4 (0; 30)2 (0; 23)0<0.00166 SJC0 (0; 23)0 (0; 3)0<0.001Number of enthesitis3 (0; 13)2 (0; 13)0<0.001Number of dactylitis0 (0; 5)00NSFibromyalgia, N (%)6 (7.9)4 (5.7)0NSN of joints with US synovitis1 (0; 32)0 (0; 7)0 (0; 6)0.001N of US enthesitis0 (0; 11)0 (0; 2)0 (0; 2)<0.001N of US tenosynovitis0 (0; 7)0 (0; 1)0 (0; 1)0.005N of joints with US osthephytes/cortical irregularities2 (0; 22)1 (0; 25)1 (0; 21)0.027N of joints with US erosions0 (0; 4)0 (0; 2)0 (0; 2)0.016N of US entheses with enthesopthytes/calcifications3 (0; 9)2 (0; 10)1 (0; 8)NSN of US enthesis with erosions0 (0; 5)0 (0; 1)0 (0; 2)0.001Fatigue (0-10)4.91 ± 3.083.46 ± 3.402.57 ± 2.86<0.001HAQ (0-3)1 (0; 2)0 (0; 2)0 (0; 1)<0.001SF36 PF61.31 ± 30.0877.46 ± 25.0289.35 ± 19.25<0.001

Across all 3 groups, all PROs correlated mainly with demographic variables, comorbidities, TJC, clinical enthesitis, skin severity, depression and fibromyalgia points (r=0.24-0.72). SymptoPsO and PsA reported similar scores of fatigue and impact on most QoL domains, significantly higher than asymptoPsO. HAQ correlated with total number of joints with US irregularities/osteophytes in PsA (r= 0.23; p=0.05), and SF36 physical function with both US inflammatory and damage variables in all three groups (r=0.24-0.34).

Conclusion:

Quality of life, disability and fatigue were more impaired in PsA and symptoPsO patients than asymptoPsO. In all groups, PROs seem to be mostly associated with socio-demographic characteristics and comorbidities rather than objective measures such as US changes or clinical variables.

References:

[1]Taylor, Arthritis Rheum 2006

[2]Bruyn,J Rheumatol 2019

Acknowledgments:

This work was supported by PARTNER fellowship.

Disclosure of Interests:

None declared

SAT0499 PREVALENCE OF ULTRASOUND FINDINGS SUGGESTIVE OF INFLAMMATORY ARTHRITIS IN CHILDREN WITH SKIN PSORIASIS (ChildEchoPso)

Background:

The prevalence of psoriasis (PsO) in children is estimated between 0.5-1% (1), and can be associated with muskuloskeletal involvement, although the prevalence and typology of such involvement is unknown. (2)

Over the last years ultrasound associated with Doppler (PDUS) has become an important tool for evaluating joint involvement in children with Juvenile Inflammatory arthritis (JIA). Several studies have shown the high sensitivity of this technique for detecting joint involvement, as well as high acceptability, due to the lack of radiation or of sedation (3).

Objectives:

To evaluate the prevalence of joints and entheses involvement in children affected by PsO.

Methods:

Observational cross-sectional study aiming at evaluating 150 consecutive children (≤16 years) affected by skin PsO and addressed by a dermatologist. For each child a standardized clinical and ultrasound evaluation of joint and entheses is performed at the following bilateral sites: a) Entheses: quadriceps tendon, proximal and distal patellar ligament, Achilles tendon, plantar fascia and extensor elbow tendon), b) joints: metacarpophalangeal, proximal and distal interphalangeal, wrist, elbow, knee, ankle, and metatarsophalangeal. PDUS evaluation is performed by an independent examiner, blinded to the clinical assessment of each subject.

Results:

41 patients were included until now, where 9 patients presented some kind of symptom (painful joint or enthesis), 24 patients have family history of psoriasis and none of them had family history of psoriatic arthritis. Demographic and clinical characteristics are shown in table 1, whilst PDUS findings in Table 2.

Table 1.

Demographic and clinical characteristics:

Total (n=41)Asymptomatic (n=32)Symptomatic (n=9)pMales22 (53.7%)18 (56.3%)4 (44.4%)NSAge9.4 ± 3.98.91 ± 3.511.3 ± 4.6NSPso duration (years)3.5 ± 3.42.9 ± 2.95.6 ± 4.5<0.05PASI5 ± 4.34.8 ± 4.55.7 ± 3.56NSBSA4.3 ± 3.94.47 ± 4.34.1 ± 2.26NSNail involvement25 (61%)19 (59.4%)6 (66.7%)NSPlaques psoriasis20 (48.8%)14 (43.8%)6 (66.7%)NSTJC ≥1, n/tot (%)9 (22%)0 (0)9 (100%)<0.001SJC ≥1, n/tot (%)2 (4.9%)0 (0)2 (22.2%)<0.05Entheseal pain, n/tot (%)6 (14.6%)0 (0)6 (66.7%)<0.001Dactylitis000NA

PASI: Psoriasis area severity index. BSA: Body surface area. TJC: Tender Joint Count. SJC: Swollen Joint Count.

Table 2

PDUS Findings:

PatientsTotal (n=41)Asymptomatic (n=32)Symptomatic (n=9)p≥1 ultrasound abnormality, n/tot (%)19 (46.3%)13 (40.6%)6 (66.7%)NS≥1 joint effusion, n/tot (%)11 (26.8%)9 (28.1%)2 (22.2%)NS≥1 synovitis, n/tot (%)3 (7.3%)1 (3.1%)2 (22.2%)NS≥1enthesitis, n/tot (%)7 (17.1%)3 (9.4%)4 (44.4%)<0.05≥1 tenosynovitis, n/tot (%)0 (0)0 (0)0 (0)NA≥1 nail with modified structure, n/tot (%)22 (53.7%)19 (59.4%)3 (33.3%)NS

Conclusion:

This study shows that the presence of ultrasound abnormalities was higher in the symptomatic group and considering the fact that the most frequent inflammatory ultrasound finding was enthesitis, we might consider the enthesis as a possible landmark for developing juvenile psoriatic arthritis.

References:

[1]Michalek et al. J Eur Acad Dermatol Venereol, 2017

[2]Petty et al. J Rheumatol, 2004

[3]Buchmann et al. Radiol Clin N Am, 2004

Acknowledgments:

This research was conducted while Luis Coronel was a PARTNER Fellow

Disclosure of Interests:

None declared

Transcriptional supercoiling boosts topoisomerase II-mediated knotting of intracellular DNA

Recent studies have revealed that the DNA cross-inversion mechanism of topoisomerase II (topo II) not only removes DNA supercoils and DNA replication intertwines, but also produces small amounts of DNA knots within the clusters of nucleosomes that conform to eukaryotic chromatin. Here, we examine how transcriptional supercoiling of intracellular DNA affects the occurrence of these knots. We show that although (−) supercoiling does not change the basal DNA knotting probability, (+) supercoiling of DNA generated in front of the transcribing complexes increases DNA knot formation over 25-fold. The increase of topo II-mediated DNA knotting occurs both upon accumulation of (+) supercoiling in topoisomerase-deficient cells and during normal transcriptional supercoiling of DNA in TOP1 TOP2 cells. We also show that the high knotting probability (P^kn ≥ 0.5) of (+) supercoiled DNA reflects a 5-fold volume compaction of the nucleosomal fibers in vivo. Our findings indicate that topo II-mediated DNA knotting could be inherent to transcriptional supercoiling of DNA and other chromatin condensation processes and establish, therefore, a new crucial role of topoisomerase II in resetting the knotting–unknotting homeostasis of DNA during chromatin dynamics.

Dynamics of supercoiled DNA with complex knots: large-scale rearrangements and persistent multi-strand interlocking

Knots and supercoiling are both introduced in bacterial plasmids by catalytic processes involving DNA strand passages. While the effects on plasmid organization has been extensively studied for knotting and supercoiling taken separately, much less is known about their concurrent action. Here, we use molecular dynamics simulations and oxDNA, an accurate mesoscopic DNA model, to study the kinetic and metric changes introduced by complex (five-crossing) knots and supercoiling in 2 kbp-long DNA rings. We find several unexpected results. First, the conformational ensemble is dominated by two distinct states, differing in branchedness and knot size. Secondly, fluctuations between these states are as fast as the metric relaxation of unknotted rings. In spite of this, certain boundaries of knotted and plectonemically-wound regions can persist over much longer timescales. These pinned regions involve multiple strands that are interlocked by the cooperative action of topological and supercoiling constraints. Their long-lived character may be relevant for the simplifying action of topoisomerases.

Non-monotonic knotting probability and knot length of semiflexible rings: the competing roles of entropy and bending energy

We consider self-avoiding rings of up to 1000 beads and study, by Monte Carlo techniques, how their equilibrium knotting properties depend on the bending rigidity. When the rings are taken from the rigid to fully-flexible limit, their average compactness increases, as expected. However, this progressive compactification is not parallelled by a steady increase of the abundance of knots. In fact the knotting probability, P_k, has a prominent maximum when the persistence length is a few times larger than the bead size. At similar bending rigidities, the knot length has, instead, a minimum. We show that the observed non-monotonicity of P_k arises from the competition between two effects. The first one is the entropic cost of introducing a knot. The second one is the gain in bending energy due to the presence of essential crossings. These, in fact, constrain the knotted region and keep it less bent than average. The two competing effects make knots maximally abundant when the persistence length is 5-10 times larger than the bead size. At such intermediate bending rigidities, knots in the chains of 500 and 1000 beads are 40 times more likely than in the fully-flexible limit.