Regulation Of Actin Dynamics By WNT‐5A: Implications For Human Airway Smooth Muscle Contraction
Bibliographic record
Abstract
An important pathophysiological feature of asthma is airway hyperresponsiveness (AHR), characterized by exaggerated bronchoconstriction in which the airway smooth muscle (ASM) is fundamentally involved. How the ASM in asthmatics differs from that in non‐asthmatics is a current focus for research. We have shown previously that WNT‐5A is increasingly expressed in ASM of mild to moderate asthmatics. WNT proteins have been implicated in the regulation of cytoskeletal filaments and microtubules, thus, we tested the hypothesis that WNT‐5A is a determinant of the contractile response of ASM through modulation of the cytoskeleton. Using bovine tracheal smooth muscle strips, we found that following pre‐incubation with recombinant WNT‐5A (500 ng/mL, 48 h), maximum isometric tension induced by histamine was increased (Emax = 1,67 fold of control, p < 0.01). We used immortalized human ASM cells to study the underlying mechanisms. In myocytes loaded with the ratiometric calcium indicator, Fura‐2, we found that neither direct exposure to WNT‐5A nor pre‐incubation (48 h) had any effect on calcium flux handling. Moreover, WNT‐5A treatment for 24 h did not yield any detectable change in mRNA expression of the major calcium channels or receptors (IP3R, SERCA2 and RyR1/2/3). However, while direct exposure to WNT‐5A (10–200 ng/mL, 24 h) had no effect on total alpha smooth muscle actin (α‐SMA) protein, it did lead to increased abundance of filamentous actin (labelled with fluorochrome‐conjugated phalloidin). These changes, which were visible after 2 hours, could be completely prevented by treatment with the Rho kinase inhibitor Y27632 (1 uM). Interestingly, ASM cells serum‐deprived for 7 days to adopt a contractile phenotype also showed greater WNT‐5A protein expression (1,99 fold of control, p < 0.05) compared to the proliferative phenotype (serum‐fed cells). We next assessed whether TGF‐β1 played an upstream role in the WNT‐5A response. We found that WNT‐5A siRNA not only blocked TGF‐β1‐induced actin polymerization, but could also abrogate TGF‐β1‐induced accumulation of α‐SMA protein. In line with this contention, adding WNT‐5A on top of TGF‐β1 synergistically induced α‐SMA protein abundance (2,21 fold of TGF‐β, p < 0.01). In summary, WNT‐5A promotes increased agonist‐induced airway smooth muscle contraction, most likely by increasing actin polymerization and actin expression in concerted action with TGF‐β1. These results may be relevant in the understanding of AHR and warrant further investigation. Support or Funding Information This work was financially supported by a NWO Vidi grant, 016.126.307.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".