Plasma membrane calcium ATPase 4 (PMCA4) is a calcium extrusion pump which may also modulate Ca2+-triggered signal transduction pathways. Previous studies postulate that PMCA4 modulates signalling via an interaction with neuronal nitric oxide synthase (nNOS) in localised plasmalemmal microdomains. The effect of PMCA4 on vascular contractility is unclear. This project has utilised PMCA4 ablated mice (PMCA4 KO (-/-)) and a novel specific PMCA4 inhibitor (termed AP2) to study the role of PMCA4 in mouse resistance artery contractility.Immunohistochemistry, Western blotting and polymerase chain reaction (PCR) confirmed the absence of PMCA4 in the brain, vasculature and ear snips obtained from PMCA4 KO (-/-) mice whereas it was present in those from wild type (WT (+/+)) mice. Pressure myography was employed to assesss contractile function of isolated, pressurised (to 60 mmHg) mesenteric resistance arteries from 3 months old male PMCA4 KO (-/-) and WT (+/+) mice, in response to high K+ physiological salt solution (KPSS) (40mM & 100mM) and noradrenaline (NA) (Log[NA] -9.0 to -5.0M). Passive lumen diameter and left and right wall thicknesses of arteries from PMAC4 KO (-/-) and WT (+/+) mice were taken at transmural pressures of 5-140 mmHg. Effects of acute PMCA4 inhibition with AP2 (10µM and 1µM), nitric oxide synthase (NOS) inhibition with LNNA (100µM) and specific nNOS inhibition with Vinyl-L-Nio (10µM) were also investigated. Effects of PMCA4 ablation and AP2 (10µM) on global intracellular Ca2+ changes ([Ca2+]i) in pressurised mesenteric arteries were assessed after loading arteries with the Ca2+-sensitive indicator indo-1. PMCA4 ablation had no effect on the magnitude of arterial constrictions or on the changes of [Ca2+]i in response to KPSS (40mM & 100mM) or to noradrenaline. The passive intra-lumen diameter, wall thickness, wall to lumen diameter and cross sectional area of mesenteric arteries across the intravascular pressure range studied were also not modulated by PMCA4 ablation. A leftwards shift in the stress to strain relationship and significant increase in beta elastic modulus (β) were revealed in arteries from PMCA4 KO (-/-) mice compared to those from WT (+/+) mice, suggesting that PMCA4 ablation reduces mesenteric arterial distensibility. Acute PMCA4 inhibition with AP2, significantly reduced arterial constrictions and the increase in [Ca2+]i in response to noradrenaline in arteries from WT (+/+) mice, but had no effect on arterial constrictions elicited by arteries from PMCA4 KO (-/-) mice. Inhibitory effects of AP2 were not present in arteries after NOS inhibition by LNNA and also after nNOS inhibition with Vinly-L-Nio. Hence, PMCA4 inhibition with AP2 reduces vascular constriction by a nNOS-dependent mechanism.In conclusion, the main findings of the study were that ablation and acute inhibition of PMCA4 with AP2 have different effects on mouse mesenteric resistance arterial contractility. This study provides more insight into PMCA4 as a significant modulator of signalling within the vasculature via effects on nNOS.

The excitation-contraction-relaxation cycle of the guinea pig ileum longitudinal smooth muscle was studied in muscles contracted by a muscarinic agent, cis-2-methyl-4-dimethylaminomethyl-1,3-dioxolane methiodide (CD) and by 60 mM KC1. Aspects of the cycle were investigated by analyzing the active transport enzyme activities in the sarcolemma, the tissue Ca depots which could release Ca for contraction and the sensitivity of the contractile responses to extracellular ion changes. Essentially net changes of intracellular Ca, Mg, Na and K content during contractions were measured by a modified 'La method'. The tissues were washed for 30 min in 160 mM Tris-HCl solution (pH 7.4) containing 10 mM LaCl₃ at 4°C in order to seal the intracellular ions in the cell and displace extracellular ions. A method to loosen the 'intercellular cementing' substance by reducing the tissue Ca and Mg was developed as an adjunct to the preparation of a sarcolemmal enriched microsomal fraction. The method reduced the tenacity of the tissue and made the tissue easy to disrupt by a mild homogenizing procedure. The method also appeared to aid the extraction of contractile proteins. The microsomal fraction was not detectably contaminated by mitochondria and was enriched with vesicles of sarcolemma, probably originating from the muscle caveolae. The sarcolemma enriched microsomal fraction had a Ca-ATPase activity that was progressively stimulated by 10⁻⁷ to 2.4 x 10⁻⁴ M free Ca²⁺ , did not require Mg and was inhibited by La. The microsomal Ca-ATPase activity was not due to contamination by actomyosin. The actomyosin Ca-r-ATPase in the soluble fraction had a higher affinity than the microsomal Ca-ATPase for Ca and for La. The microsomal Ca-ATPase activity was postulated to be associated with an active Ca pump thought to he located in the cayeolae. The microsomal fraction had a Mg-dependent ATPase that could Be stimulated by Na, but K and ouabain had very little additional effect. The addition of an activating factor in the soluble fraction conferred some K and ouabain sensitivity to the Mg-dependent Na-ATPase, which indicated that a Na,K-ATPase was present in this tissue. Low doses of ouabain contracted the longitudinal ileum but the responses were not antagonized by raising the external K concentration five fold, as would be expected if ouabain acted by inhibiting the Na,K-ATPase. However, the ouabain response was rapidly lost when extracellular Ca was removed from the medium and the decline of the response followed the same time course as the loss of extracellular Ca. The peak of the ouabain contraction coincided with significant increases of intracellular Ca and Na, but K loss was not apparent until relaxation ensued. The results suggested that ouabain has an early direct effect on membrane permeability before it inhibited the Na,K-ATPase. CD (2 x 10⁻⁷ M) and 60 mM KCl induced phasic and tonic contractions of the longitudinal muscle of the ileum. The phasic contraction declined from 100% to 7% over 10 min when Ca was omitted from the physiological medium. This decline followed the time course of the loss of extracellular Ca. This, together with the fact that low concentrations of LaCl₃ inhibited the phasic component, indicated that Ca bound to the outer aspect of the cell was responsible for the phasic component. The tonic component was lost more rapidly than the phasic component when the Ca was removed from the Tyrode's solution. The tonic component seemed activated by free Ca mobilized from the extracellular space. The extracellular origin of the Ca for contraction was consistent with the observed small net gain of intracellular Ca that occurred during the phasic and tonic contractions. The minimal volume of the sarcoplasmic reticulum and the abundance of caveolae was also consistent with the high sensitivity of the tissue to extracellular Ca concentrations. The intracellular Ca gained during contraction wa,s extruded within 30 sec after the CD or 60 mM KCl were washed out of the tissue bath, Following washout of CD, the muscle was quiescent for the 20 to 30 min 'equilibration' phase. Spontaneous activity was absent during this phase and tension was below baseline. After a maximal CD contraction, a second response to CD or to 60 mM KCl induced during the 'equilibration' phase had an altered or desensitized biphasic appearance. Responses of the muscle to CD for 10 min were accompanied by a cytoplasmic loss of K. After washout of CD, the K was regained slowly over 20 to 30 min. Stimulation of the tissue by 60 mM KCl did not cause a loss of K from the muscle nor did it cause desensitization of the muscle. Higher extracellular K concentrations decreased the time required after CD contractions for the return of spontaneous activity and prevented muscle desensitization to repeated doses of CD, probably by accelerating the return of intracellular K levels to normal. It was proposed that during contraction, elevated intracellular Ca activated K channels, thereby increasing K permeability and causing the 'after-hyperpolarization' and subsequent desensitization which follows muscarinic induced contractions. / Pharmaceutical Sciences, Faculty of / Graduate

Objective - The majority of apoptotic cells in atherosclerotic lesions are macrophages. However, the pathogenic role of macrophage apoptosis in the development of atherosclerosis remains unclear. Elevated expression of Bax, one of the pivotal proapoptotic proteins of the Bcl-2 family, has been found in human atherosclerotic plaques. Activation of Bax also occurs in free cholesterol-loaded and oxysterol-treated mouse macrophages. In this study, we examined the effect of Bax deficiency in bone marrow-derived leukocytes on the development of atherosclerosis in low-density lipoprotein receptor-null (LDLR-/-) mice. Methods and Results - Fourteen 8-week-old male LDLR-/- mice were lethally irradiated and reconstituted with either wild-type (WT) C57BL6 or Bax-null (Bax-/-) bone marrow. Three weeks later, the mice were challenged with a Western diet for 10 weeks. No differences were found in the plasma cholesterol level between the WT and Bax-/- group. However, quantitation of cross sections from proximal aorta revealed a 49.2% increase (P=0.0259) in the mean lesion area of the Bax-/- group compared with the WT group. A 53% decrease in apoptotic macrophages in the Bax-/- group was found by TUNEL staining (P<0.05). Conclusions - The reduction of apoptotic activity in macrophages stimulates atherosclerosis in LDLR-/- mice, which is consistent with the hypothesis that macrophage apoptosis suppresses the development of atherosclerosis.

The interaction between CD40 ligand (CD154) expressed on activated T cells and its receptor, CD40, has been shown to play a role in the onset and maintenance of autoimmune inflammation. Recent studies suggest that CD154+T cells also contribute to the regulation of atherogenesis due to their capacity to activate CD40+cells of the vasculature, including vascular smooth muscle cells (VSMC). The present study evaluated the signalling events initiated through CD40 ligation which culminate in VSMC chemokine production. CD40 ligation resulted in the phosphorylation/activation of mitogen-activated protein kinases (MAPKs), extracellular signal-regulated kinases 1 and 2 (ERK1/2), and p38, but not c-jun N-terminal kinase. Inhibition of both ERK1/2 and p38 activity abrogated CD40 stimulation of IL-8 and MCP-1 production. CD40-mediated induction of chemokines also showed dependence on the Src family kinase activity. The Src kinase inhibitor, PP2, was found to inhibit CD40-induced phosphorylation of ERK1/2 as well as activation of IκB kinase. An evaluation of Src kinases that may be important in CD40 signalling identified Lyn as a potential candidate. These data indicate that CD40 signalling in VSMC activates a Src family kinase-initiated pathway that results in the induction of MAPK activities required for successful induction of chemokine synthesis.

Smooth muscle contraction regulates the size of the blood vessel lumen which directly affects the mechanical response of the vessel. Folding in arteries has been observed in arteries during excessive contraction, known as a coronary artery spasm. The interplay of muscle contraction, geometry, and material responses and their effects on stability can be understood through mathematical models. Here, we consider a three-layer cross-sectional model of a coronary artery with anisotropic properties and intimal thickening, and perform a linear stability analysis to investigate the circumferential folding patterns that emerge due to muscle contraction. Our model shows that a critical level of contractile activity yields a uniform strain distribution across the arterial wall. When the muscle is contracted above this critical level, the tissue behaves isotropically and it is more prone to circumferential instability. This theoretical framework could serve as a valuable tool to understand the relationship between arterial lumen morphology and wall contraction in health and disease.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第17946号 / 医博第3830号 / 新制||医||1000(附属図書館) / 30776 / 京都大学大学院医学研究科医学専攻 / (主査)教授 稲垣 暢也, 教授 小西 郁生, 教授 安達 泰治 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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1. We studied the effect of intracellular angiotensin II (Ang II) and related peptides on rat aortic contraction, whether this effect is pharmacologically distinguishable from that induced by extracellular stimulation, and determined the Ca2+ source involved. 2. Compounds were delivered into the cytoplasm of de-endothelized aorta rings using multilamellar liposomes. Contractions were normalized to the maximum obtained with phenylephrine (10-5 M). 3. Intracellular administration of Ang II (incorporation range: 0.01-300 nmol mg-1) resulted in a dose-dependent contraction, insensitive to extracellular administration (10-6 M) of the AT1 receptor antagonist CV11947, the AT2 receptor antagonist PD 123319, or the non-selective AT receptor antagonist and partial agonist saralasin ([Sar1,Val5,Ala8]-Ang II (P < 0.05). 4. Intracellular administration of CV11947 or PD 123319 right shifted the dose-response curve about 1000 fold or 20 fold, respectively. PD 123319 was only effective if less than 30 nmol mg-1 Ang II was incorporated. 5. Contraction was partially desensitized to a second intracellular Ang II addition after 45 min (P < 0.05). 6. Intracellular administration of Ang I and saralasin also induced contraction (P < 0.05). Both responses were sensitive to intracellular CV11947 (P < 0.05), but insensitive to PD 123319. The response to Ang I was independent of intracellular captopril. 7. Contraction induced by extracellular application of Ang II and of Ang I was abolished by extracellular pre-treatment with saralasin or CV11947 (P < 0.05), but not with PD 123319. Extracellular saralasin induced no contraction. 8. Intracellular Ang II induced contraction was not affected by pre-treatment with heparin filled liposomes, but completely abolished in Ca2+-free external medium. 9. These results support the existence of an intracellular binding site for Ang II in rat aorta. Intracellular stimulation induces contraction dependent on Ca2+-influx but not on Ins(1,4,5)P3 mediated release from intracellular Ca2+-stores. Intracellular Ang I and saralasin induce contraction, possibly via the same binding site. Pharmacological properties of this putative intracellular receptor are clearly different from extracellular stimulated AT1 receptors or intracellular angiotensin receptors postulated in other tissue.

According to the CDC, the prevalence of diabetes has increased from 3.3% in 2004 to over 10.1% by 2019 (Prevalence of Diagnosed Diabetes). The United States Department of Agriculture (USDA) recommends that total fat intake should be between 20 - 35% of the total calories an individual consumes in a day and yet the Center for Disease Control and Prevention (CDC) reports that on average, total fat consumption makes up 35.8% of a person’s diet (Dietary guidelines, 2020 & CDC, 2021 respectively). According to Parrish, “dietary fat does not have an immediate effect on blood sugar levels, but consuming a meal high in fat can slow digestion and make it more difficult for insulin to work” (Parrish, 2015). Chronic diabetes can result in hypocontractility of the bladder. Contractility of the bladder is controlled by a multitude of receptors, ligands, and kinases. One receptor our group feels contributes is neuropilin 2. Our group has reported expression of neuropilin 2 in the smooth muscle of the bladder and has shown that expression induces cytoskeleton relaxation. Thus, it is thought that if neuropilin 2 expression is reduced, that potentially that hypocontractility of the bladder can be attenuated. In an in vivo model of diabetes using mice on a high fat diet for 5 months, we observed minimal changes in bladder histology, and variable Nrp2 expression. In silico analysis of data from in vivo and in vitro models of diabetes identified Nrp2 transcriptional induction compared to controls and a connection with multiple differentially expressed genes in the Nrp2 signaling pathway linked with biological processes related to a diabetic pathological state. An in vitro model of diabetes which subjected rat bladder contractile cells to high glucose identified significant cytoskeletal changes, increases in Nrp2 expression, and decreased contractility. Knock-down of Nrp2 using siRNA resulted in increased contractility of smooth muscle cells on collagen gels. These data suggest that Nrp2 signaling is altered under diabetic conditions and could be targeted to attenuate diabetes induced bladder hypocontractility. / 2025-07-06T00:00:00Z

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