ORIGINAL RESEARCHPentoxifylline Attenuates Transforming Growth Factor-β1-Stimulated Elastogenesis in Human Tunica Albuginea-Derived Fibroblasts Part 2: Interference in a TGF-β1/Smad-Dependent Mechanism and Downregulation of AAT1
Introduction
Transforming growth factor-beta1 (TGF-β1) is a potent modulator of the ECM in a variety of human fibrotic diseases [1]. It is known to be intimately related to the Peyronie's disease (PD) phenotype, and treatment with TGF-β1 has been shown to induce a PD-like condition in animal models 2, 3, 4. Much of this effect has been attributed to TGF-β1-induced enhancement of collagen production in fibroblasts although alternate pathways mediated by other members of the TGF-β1 superfamily (such as myostatin) have been shown to be involved in the pathophysiology of PD 5, 6, 7. TGF-β1 has also been demonstrated to increase elastin mRNA levels in both dermal and lung fibroblasts 8, 9.
TGF-β1 exerts the majority of its downstream effects via action on Smad proteins, a family of TGF receptor substrates that have the capacity to act as transcription factors in the cell nucleus [1]. Smad proteins frequently interact with one another during the course of activation; specifically, Smad2 and 3 typically interact together, whereas Smad1 and 5 also share activity. Although the majority of Smad proteins have stimulatory effects on gene transcription, the inhibitory Smads (Smad6 and 7) inhibit the activity of other Smad proteins 10, 11. The Smad proteins have been shown to play very important roles in the modulation of collagen I production and thereby a critical role in extracellular fibrotic conditions, such as PD [1].
Pentoxifylline (PTX), a nonselective phosphodiesterase inhibitor with anti-inflammatory properties in vivo and in vitro, has been shown in both in vitro and in vivo (rat) experiments to induce regression of collagen and TGF-β1-induced plaque [12]. We have demonstrated that TGF-β1 enhances collagen and elastin production as well as elastogenesis in tunica albuginea-derived fibroblast cells (TADF). In this model system elastogenesis (deposition of elastin fibers) is attenuated by pretreatment with PTX. The current study is an assessment of the impact of TGF-β1 with or without PTX on elastin metabolism in tunica albuginea derived fibroblasts (TADF) at the mRNA, protein, and cellular signaling level [13].
Section snippets
Tissue Harvesting and Cell Culture
Fibrotic tunica plaques (PT) were harvested from 12 patients with chronic (>12 months duration) PD who were undergoing surgery for correction of penile curvature. Normal tunica (NT) was harvested from six patients who were undergoing penile prosthesis placement. All cavernosal tissue was stripped from the biopsy specimens so as to ensure a pure culture of tunica-derived tissues. Our Institutional Committee on Human Research approved all procedures regarding the collection and use of human
TGF-β1 Stimulates the Synthesis of Elastin in a Time- and Dose-Dependent Manner in TADF Cells
TGF-β1 increased elastin mRNA expression in cultured TADF in a dose-dependent fashion with a plateau effect at doses greater than 0.1 ng/mL for both PT and NT TADF. The magnitude of increase in NT was significantly less than PT at doses greater than 1 ng/mL (Figure 1A). Steady-state elastin mRNA levels were significantly increased in TGF-β1 treated TADF relative to untreated TADF. Increased elastin mRNA was detected within 4 hours in PT cells; interestingly, NT TADF did not significantly increase
Discussion
The TGF-β superfamily binds to two receptors, TβRI and TβRII, to regulate downstream molecules and subsequent gene expression. After the TGF-β1 ligand binds to a receptor, signal transduction occurs predominantly by members of the Smad family. The activation of Smad proteins is achieved through the phosphorylation of specific receptor-regulated Smads (R-Smads) by an activated receptor. This leads to formation of “Smad complexes” that accumulate in the nucleus and regulate target genes 10, 11.
Conclusions
Production of collagen and elastin in TADF cells is stimulated by TGF-β1; this effect is associated with increased activation of the dual TGF-β/Smad pathways. Pretreatment of TADF with PTX attenuates the TGF-β1 mediated increase in elastogenesis, possibly by downregulation of Smad1/5 via an iSmad6 dependent mechanism. As there were no PTX-mediated changes in expression/activity of the proteins essential to assembly of elastin fibers in the ECM, the precise mechanisms by which PTX attenuates
Category 1
- (a)
Conception and Design
Guiting Lin; Tom F. Lue; Ching-Shwun Lin
- (b)
Acquisition of Data
Guiting Lin; Hongxiu Ning; Lia Banie; Gang Liu; Yun-Ching Huang
- (c)
Analysis and Interpretation of Data
Guiting Lin; Alan W. Shindel; Ching-Shwun Lin; Tom F. Lue
Category 2
- (a)
Drafting the Article
Alan W. Shindel
- (b)
Revising It for Intellectual Content
Guiting Lin; Tom F. Lue; Alan W. Shindel; Ching-Shwun Lin
Category 3
- (a)
Final Approval of the Completed Article
Guiting Lin; Tom F. Lue; Alan W. Shindel
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2020, Sexual MedicineCitation Excerpt :This transformation reflects pertinent urologic studies published during the study period. In 2010, 2 basic science articles were published with evidence that pentoxifylline attenuates collagen deposition and elastogenesis in tunica albuginea–derived fibroblasts.13,14 In the same year, a double-blind, placebo-controlled study comparing oral pentoxifylline with placebo in patients with early, chronic PD suggested significantly increased self-reported positive response and improvement in penile curvature, International Index of Erectile Function score, and mean peak systolic velocities in the pentoxifylline group.15
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2015, Asian Journal of UrologySuperficial Dermal and Fascial Fibromatoses
2014, Pathobiology of Human Disease: A Dynamic Encyclopedia of Disease MechanismsOffice-based management of impotence and peyronie's disease
2013, Urologic Clinics of North AmericaCitation Excerpt :Pentoxifylline (PTX) is a nonspecific phosphodiesterase inhibitor, with combined antiinflammatory and antifibrogenic properties by downregulating TGF-b and increasing fibrinolytic activity. Its use has been suggested in the management in PD, after studies have shown its effects in vitro to attenuate both collagen fiber deposition and elastogenesis.145,146 Although small, uncontrolled studies suggested some improvement in penile curvature, this has not been demonstrated in large, placebo-controlled trials.
The pathophysiology of Peyronie's disease
2013, Arab Journal of UrologyCitation Excerpt :Furthermore, the expression of elastin mRNA and protein is up-regulated in TA-derived fibroblasts by TGF-β 1. Pentoxifylline had no effect on elastin production, but attenuates elastogenesis in TA-derived fibroblasts through an Alpha-1 antitrypin-related mechanism [52]. PD is one of the most puzzling diseases in urology.
Conflict of Interest: None.