| 1. |
- Zhu, Baoyi, et al.
(författare)
-
Similar regulatory mechanisms of caveolins and cavins by myocardin family coactivators in arterial and bladder smooth muscle
- 2017
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:5
-
Tidskriftsartikel (refereegranskat)abstract
- Caveolae are membrane invaginations present at high densities in muscle and fat. Recent work has demonstrated that myocardin family coactivators (MYOCD, MKL1), which are important for contractile differentiation and cell motility, increase caveolin (CAV1, CAV2, CAV3) and cavin (CAVIN1, CAVIN2, CAVIN3) transcription, but several aspects of this control mechanism remain to be investigated. Here, using promoter reporter assays we found that both MKL1/MRTF-A and MKL2/MRTF-B control caveolins and cavins via their proximal promoter sequences. Silencing of MKL1 and MKL2 in smooth muscle cells moreover reduced CAV1 and CAVIN1 mRNA levels by well over 50%, as did treatment with second generation inhibitors of MKL activity. GATA6, which modulates expression of smooth muscle-specific genes, reduced CAV1 and CAV2, whereas the cavins were unaffected or increased. Viral overexpression of MKL1 and myocardin induced caveolin and cavin expression in bladder smooth muscle cells from rats and humans and MYOCD correlated tightly with CAV1 and CAVIN1 in human bladder specimens. A recently described activator of MKL-driven transcription (ISX) failed to induce CAV1/CAVIN1 which may be due to an unusual transactivation mechanism. In all, these findings further support the view that myocardin family coactivators are important transcriptional drivers of caveolins and cavins in smooth muscle.
|
|
| 2. |
- Andersson, Karl Erik, et al.
(författare)
-
Changes in the rat urinary bladder after the relief of outflow obstruction – tracing targets for treatment of persistent symptoms in patients
- 2022
-
Ingår i: Frontiers in Urology. - : Frontiers Media SA. - 2673-9828. ; 2
-
Forskningsöversikt (refereegranskat)abstract
- Studies on patients with bladder outflow obstruction who have undergone surgery for benign prostatic hyperplasia, successfully relieving the obstruction, have revealed a persistence of storage symptoms associated with detrusor overactivity (DO) in 20% to 40% of patients. To study the underlying mechanisms, we have used a common rat model of obstruction/de-obstruction, assuming that non-voiding contractions can be used as a surrogate parameter for DO in humans. Using microarray analysis and electron microscopic images from obstructed and de-obstructed bladder tissue we have tried to identify changes that could serve as a basis for the search of new targets for drugs. Even if voiding function is rapidly normalized after release of outflow obstruction and many of the morphological changes are reversed, the microarray analysis revealed that the de-obstructed rat bladder has gene expressions, structural, and functional properties that make it distinctly different from both control and obstructed bladders. We suggest that whole bladder arrays can be used for identifying cellular mechanisms that could be targets for drugs meant for treatment of persistent DO and LUTS after de-obstruction. Based on available array information for some membrane receptors and morphologic structures with corresponding changes in bladder function, it seems worthwhile to re-assess the development potential for e.g., endothelin receptor antagonists, purinergic receptor antagonists and Rho-kinase inhibitors.
|
|
| 3. |
- Arner, Anders, et al.
(författare)
-
Effects of Ca2+ on force-velocity characteristics of normal and hypertrophic smooth muscle of the rat portal vein
- 1985
-
Ingår i: Acta Physiologica Scandinavica. - 0001-6772. ; 124:4, s. 525-533
-
Tidskriftsartikel (refereegranskat)abstract
- Portal hypertension was induced in rats by partial ligation of the hepatic branches of the portal vein. After 5 days of hypertension the portal veins were taken out and mounted for isometric and quick-release experiments. Portal veins from sham-operated normal rats served as controls. The ligated veins had an increased cross-sectional area, indicating smooth-muscle hypertrophy. Although the absolute magnitude of active force of these veins was increased, the active force per cross-sectional area was decreased, indicating an alteration in the properties of the contractile system. No difference in the Ca2+ concentration-response relations to K+-activated intact control and hypertrophic veins was found. In chemically skinned preparations, devoid of functional plasma membranes, the hypertrophic veins had similar Ca2+ sensitivity (in the presence of I microM calmodulin) but a lower force per cross-sectional area. Force-velocity relations were determined in K+-activated intact preparations. In control veins a reduction in extracellular Ca2+ was associated with a significant reduction in both isometric force and maximal shortening velocity (Vmax). In hypertrophic veins the decreased isometric force at maximal activation was associated with a low Vmax. A comparison between hypertrophic and submaximally stimulated control vessels showed corresponding Vmax and isometric force values. We conclude that the low isometric force of hypertrophic veins is associated with a lower rate of cross-bridge turnover. This could be an effect of alterations in the activation mechanisms or in the intrinsic properties of the contractile system itself.
|
|
| 4. |
- Arner, Anders, et al.
(författare)
-
Energy turnover and lactate dehydrogenase activity in detrusor smooth muscle from rats with streptozotocin-induced diabetes
- 1993
-
Ingår i: Acta Physiologica Scandinavica. - 0001-6772. ; 147:4, s. 375-383
-
Tidskriftsartikel (refereegranskat)abstract
- Force generation and tissue glucose metabolism were measured in the urinary bladder smooth muscle from rats with streptozotocin-induced diabetes (7-8 wk duration). Bladder wet wt was almost 4-fold higher in the diabetic animals compared with the untreated controls. Morphological analysis showed that the growth was associated with hypertrophy of the smooth muscle component in the bladder wall. Force generation of isolated bladder strip preparations was measured in vitro at different ambient oxygen tensions. Activation of intramural nerves, with electrical field stimulation, induced contractions that were unaffected by reduction of oxygen tension down to PO2 100 mmHg for both control and diabetic muscle strips. At zero PO2 force was reduced by approximately 10-20%, in both groups. High-K+ solution induced 'tonic' contractions that were slightly more inhibited by lowering PO2. At intermediate PO2 (between 100 and 20 mmHg) the diabetic muscle gave slightly higher force. At zero PO2 no significant difference could be detected between strips from control and diabetic animals. Oxygen consumption and lactate production in the preparations were determined at a PO2 of 290 mmHg and related to the volume of smooth muscle. At zero PO2, lactate formation increased 3- to 4-fold. The metabolic tension cost was lower at zero PO2. No differences in basal and contraction related metabolic rates could be detected between the two groups under normoxic and anoxic conditions. The maximal activity of lactate dehydrogenase (LDH) determined in tissue samples was about 2-fold higher in the diabetic bladder muscle.(ABSTRACT TRUNCATED AT 250 WORDS)
|
|
| 5. |
- Arner, Anders, et al.
(författare)
-
Intracellular calcium in hypertrophic smooth muscle from rat urinary bladder
- 2007
-
Ingår i: Scandinavian Journal of Urology and Nephrology. - : Informa UK Limited. - 0036-5599 .- 1651-2065. ; 41:4, s. 270-277
-
Tidskriftsartikel (refereegranskat)abstract
- Objective. To explore whether infravesical outlet obstruction is associated with alterations in calcium activation of detrusor smooth muscle. Material and methods. Outlet obstruction was created by partial ligature of the urethra in female rats. Western blotting was performed using an antibody against the cytoplasmatic region of the alpha(1c) subunit of the L- type Ca2(+) channel. Intracellular calcium was measured using Fura-2 in detrusors that had been obstructed for 10 days and activated by high K+ concentrations at different extracellular Ca2(+) concentrations. The rate of force development after rapid opening of L- type Ca2(+) channels was measured in contractions initiated by flash photolysis of nifedipine in Ca2(+) containing depolarizing solution. Results. Bladder weight increased from 6293 to 254943 mg after 10 days of obstruction. Expression of the alpha(1c) subunit increased after 3 days and continued to increase until it was about fourfold greater after 10 days; however, it had not increased further at 6 weeks. This change was reversible after removal of obstruction. Activation with K+ produced a stable force at different extracellular Ca2(+) concentrations, with no difference in response between controls and rats that had been obstructed for 10 days. Intracellular Ca2(+) concentrations were lower in the obstructed group, showing that the calcium sensitivity of the contraction force had increased. The delay between the opening of L- type channels and the onset of contraction was longer in obstructed detrusors. Conclusions. Growth of detrusor muscle following obstruction is accompanied by attenuated calcium transients following activation, despite upregulation of L- type Ca2(+) channels. The Ca2(+) sensitivity of contraction was increased in obstructed detrusors. We suggest that the decreased surface: volume ratio in hypertrophic smooth muscle cells is partly involved in the lowered Ca2(+) transients. The increases in L- type calcium channels and in calcium sensitivity may be compensatory mechanisms.
|
|
| 6. |
- Arner, Anders, et al.
(författare)
-
Metabolism and force in hypertrophic smooth muscle from rat urinary bladder
- 1990
-
Ingår i: American Journal of Physiology: Cell Physiology. - 1522-1563. ; 258:5 Pt 1, s. 923-932
-
Tidskriftsartikel (refereegranskat)abstract
- Ten days of urinary outlet obstruction in the rat induced a threefold increase in bladder weight. Active force of control and hypertrophic bladder muscle strips was measured at varying PO2 levels after high-K+, carbachol, or electrical field stimulation. Highest force output was obtained with carbachol. Force per muscle area was lower in the hypertrophic muscles. The basal rates of oxygen consumption and lactate formation were similar in the two groups. The metabolic tension cost (ATP turnover/active force) was similar in the two groups for activation with high K+ and carbachol. In anoxia the active force decreased, but this was less pronounced in the hypertrophied muscle. Hypertrophied muscle could, in contrast to the controls, maintain a sustained K+ contracture in anoxia. Basal metabolic rates and tension cost were markedly reduced in anoxia for both groups. The lower force per area with unaltered tension cost, in hypertrophic muscles under all experimental conditions, may reflect unaltered intrinsic properties of the contractile system, although the amount of contractile material has decreased relative to cell volume. The increased resistance to anoxia may reflect a metabolic adaptation to impaired oxygen supply to the hypertrophied tissue.
|
|
| 7. |
- Arner, Anders, et al.
(författare)
-
Structural and mechanical adaptations in rat aorta in response to sustained changes in arterial pressure
- 1984
-
Ingår i: Acta Physiologica Scandinavica. - 0001-6772. ; 122:2, s. 119-126
-
Tidskriftsartikel (refereegranskat)abstract
- Structural and mechanical adaptations in response to sustained changes in arterial pressure were studied on abdominal aorta of the male rat. Two models were used: 1. Aortic ligature (L), immediately below the renal arteries producing hypotension distal to the knot (duration before sacrifice 6 weeks or 3 months). 2. One-clip renal hypertensive rats (H) (duration 6 weeks). Normotensive sham-operated rats (C) served as controls. At sacrifice mean tail artery pressure was L: 58 +/- 1, C: 110 +/- 3, and H: 163 +/- 5 mmHg (SE, N=6). Segments of abdominal aorta were mounted in vitro for determination of their length-tension relations (activation: High-K+ solution with 2.5 mM Ca2+). At end of experiments the vessels were supramaximally stimulated at optimal circumference (1o) for active force (activation: High-K+ solution with 10 mM Ca2+, and 10(-5) M noradrenaline), and then fixated for light and electron microscopy. Passive and active length-tension relations were shifted towards lower and higher circumference values for hypo- and hypertensive vessels, respectively. The 1o values were L: 3.60 +/- 0.13, C: 4.44 +/- 0.19, and H: 4.91 +/- 0.29 mm. The media thickness at 1o was reduced in L: 56.0 +/- 3.3, and increased in H: 81.3 +/- 2.4 compared to C: 73.4 +/- 1.8 micron. Maximal active wall stress was L: 46.6 +/- 9.8, C: 74.2 +/- 7.0, and H: 83.8 +/- 7.7 mN/mm2. Intracellular volume (ICV) in the media was L: 30 +/- 2, C: 45 +/- 3, and H: 44 +/- 1% (n=4 for each).
|
|
| 8. |
- Balakrishnan, N, et al.
(författare)
-
Biocompatibility of nitinol and stainless steel in the bladder: An experimental study
- 2005
-
Ingår i: Journal of Urology. - : Ovid Technologies (Wolters Kluwer Health). - 1527-3792 .- 0022-5347. ; 173:2, s. 647-650
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose: We tested the biocompatibility of nitinol, a nickel titanium alloy, and stainless steel (SS) as bladder implant materials. Materials and Methods: Rats received a nitinol implant, an SS implant or were sham controls. Two, 3, 6 and 8 weeks following implantation 24-hour voiding behavior studies were per-formed to investigate bladder irritation. All animals were sacrificed 8 weeks after implantation and a sample of urine was aspirated for culture. The bladders were examined by light microscopy and scanning electron microscopy (SEM). Results: No visible encrustations or infections were noted in urine. Voiding frequency in the light period 6 weeks after implantation was significantly decreased in the 2 implant groups compared with sham controls. There were no other significant differences in frequency or mean volume per void in the light or dark periods at any time point. Light microscopy demonstrated similar implant tissue effects in all groups with little or no inflammation or fibrosis. Under SEM all implants showed a brittle, amorphous coating devoid of cells. The transition between the urothelium, mucosa and the rod was smoother for SS than for nitinol, suggesting an affinity of SS for mucosa. In all nitinol rods discontinuity was present between the mucosa and rod. Conclusions: Nitinol and SS do not cause more irritation than the effects of surgery alone and the 2 materials seem to be biocompatible in the bladder. Nitinol may be more inert than SS based on SEM results.
|
|
| 9. |
- Chen, Y, et al.
(författare)
-
Increase in insulin-like growth factor I in hypertrophying smooth muscle
- 1994
-
Ingår i: American Journal of Physiology - Endocrinology and Metabolism. - 1522-1555. ; 266:2 Pt 1, s. 224-229
-
Tidskriftsartikel (refereegranskat)abstract
- The present study focuses on the role of the insulin-like growth factor (IGF) system in the development of smooth muscle hypertrophy. Hypertrophy was initiated by partial ligation of portal vein or urethra in female Sprague-Dawley rats weighing approximately 220 g. Levels of mRNA were analyzed by solution hybridization. Seven days after ligation, the wet weight of the portal vein was increased about threefold and the concentration of IGF-I mRNA was increased fourfold. The bladder wet weight was increased twofold 3 days after ligation and fourfold 10 days after ligation. IGF-I mRNA in the bladder was elevated 3-fold after 3 days and 2.5-fold after 10 days, whereas IGF binding protein 2 mRNA was increased approximately 2-fold after 3 days and 5-fold after 10 days. IGF-I receptor mRNA in the hypertrophying bladder remained unchanged. Increased levels of IGF-I were demonstrated with immunohistochemistry in both hypertrophying portal vein and urinary bladder. The results show a specific increase in IGF-I mRNA as well as an increased IGF-I immunoreactivity during hypertrophy of smooth muscle, which suggests that the local IGF-system may play a role in smooth muscle hypertrophy.
|
|
| 10. |
- Ekman, Mari, et al.
(författare)
-
HIF-mediated metabolic switching in bladder outlet obstruction mitigates the relaxing effect of mitochondrial inhibition.
- 2014
-
Ingår i: Laboratory Investigation. - : Elsevier BV. - 1530-0307 .- 0023-6837. ; 94:5, s. 557-568
-
Tidskriftsartikel (refereegranskat)abstract
- Prior work demonstrated increased levels of hypoxia-inducible factor-1α (HIF-1α) in the bladder following outlet obstruction, associated with bladder growth and fibrosis. Here we hypothesized that HIF induction in outlet obstruction also switches energetic support of contraction from mitochondrial respiration to glycolysis. To address this hypothesis, we created infravesical outlet obstruction in female Sprague-Dawley rats and examined HIF induction and transcriptional activation. HIF-1α increased after 6 weeks of outlet obstruction as assessed by western blotting and yet transcription factor-binding site analysis indicated HIF activation already at 10 days of obstruction. Accumulation HIF-2α and of Arnt2 proteins were found at 10 days, providing an explanation for the lack of correlation between HIF-1α protein and transcriptional activation. HIF signature targets, including Slc2a1, Tpi1, Eno1 and Ldha increased in obstructed compared with sham-operated bladders. The autophagy markers Bnip3 and LC3B-II were also increased at 6 week of obstruction, but electron microscopy did not support mitophagy. Mitochondria were, however, remodeled with increased expression of Cox4 compared with other markers. In keeping with a switch toward glycolytic support of contraction, we found that relaxation by the mitochondrial inhibitor cyanide was reduced in obstructed bladders. This was mimicked by organ culture with the HIF-inducer dimethyloxalylglycine, which also upregulated expression of Ldha. On the basis of these findings, we conclude that HIF activation in outlet obstruction involves mechanisms beyond the accumulation of HIF-1α protein and that it results in a switch of the energetic support of contraction to anaerobic glycolysis. This metabolic adaptation encompasses increased expression of glucose transporters and glycolytic enzymes combined with mitochondrial remodeling. Together, these changes uphold contractility when mitochondrial respiration is limited.Laboratory Investigation advance online publication, 3 March 2014; doi:10.1038/labinvest.2014.48.
|
|
