Hyperthermia at 43 degrees C for 2h inhibits the proliferation of vascular smooth muscle cells, but not endothelial cells

Nanogold-coated stent facilitated non-invasive photothermal ablation of stent thrombosis and restoration of blood flow

In-stent restenosis (ISR) and stent thrombosis (ST) are the most serious complications of coronary angioplasty and stenting. Although the evolution of drug-eluting stents (DES) has significantly restricted the incidence of ISR, they are associated with an enhanced risk of ST. In the present study, we explore the photothermal ablation of a thrombus using a nano-enhanced thermogenic stent (NETS) as a modality for revascularization following ST. The photothermal activity of NETS, fabricated by coating bare metal stents with gold nanorods generating a thin plasmonic film of gold, was found to be effective in rarefying clots formed within the stent lumen in various in vitro assays including those under conditions mimicking blood flow. NETS implanted in the rat common carotid artery generated heat following exposure to a NIR-laser that led to effective restoration of blood flow within the occluded vessel in a model of ferric chloride-induced thrombosis. Our results present a proof-of-concept for a novel photothermal ablation approach by employing coated stents in the non-invasive management of ST.

Heating of Large Endovascular Stents and Stent Grafts in Magnetic Particle Imaging-Influence of Measurement Parameters and Isocenter Distance

PURPOSE

Magnetic particle imaging (MPI) is a tomographic imaging modality with the potential for cardiovascular applications. In this context, the extent to which stents are heated should be estimated from safety perspective. Furthermore, the influence of the measurement parameters and stent distance to the isocenter of the MPI scanner on stent heating were evaluated.

MATERIALS AND METHODS

Nine different endovascular stents and stent grafts were tested in polyvinyl-chloride tubes. The stents had diameters from 10 to 31 mm, lengths between 25 and 100 mm and were made from stainless steel, nitinol or cobalt-chromium. The temperature differences were recorded with fiber-optic thermometers. All measurements were performed in a preclinical commercial MPI scanner. The measurement parameters were varied (drive field strengths: 3, 6, 9, 12 mT and selection field gradients: 0, 1.25 and 2.5 T/m). Furthermore, measurements with different distances to the scanner's isocenter were performed (100 to 0 mm).

RESULTS

All stents showed heating (maximum 53.1 K, minimum 4.6 K). The stent diameter directly correlated with the temperature increase. The drive field strength influenced the heating of the stents, whereas the selection field gradient had no detectable impact. The heating of the stents decreased with increasing distance from the scanner's isocenter and thus correlated with the loss of the scanner's magnetic field.

CONCLUSION

Stents can cause potentially harmful heating in MPI. In addition to the stent diameter and design, the drive field strength and the distance to the MPI scanner's isocenter must be kept in mind as influencing parameters.

Sensors-based monitoring and treatment approaches for in-stent restenosis

Cardiovascular disease (CVD) can progressively narrow arteries due to plaque accumulation on the inner walls of the blood vessels, which results in an obstructed blood flow, leading to heart attack, stroke, and even death if the obstruction is severe. A popular treatment for the disease is to use an intravascular mechanical device called the stent to achieve an immediate restoration of blood flow. However, the physical stimulation induced by the stent expansion can cause inflammation of the vessel tissue. As one of the most common post-stenting complications, re-narrowing of the vessel is the main pathology that leads to in-stent restenosis (ISR), induced by the excess growth of the tissue over the deployed stent. The ISR is widely recognized as a significant cause of death globally if early symptoms are not detected. Hence, monitoring and early diagnosis indeed matter when it comes to treatment. The latest technologies for monitoring and treatments of ISR were reviewed in this work, and the potential issues and suggestions related to the reported technologies were presented. The target of this review aims to positively prompt researchers to develop an advanced stent system in terms of its electromechanical performance, size, functional feature, feasibility, and reliability.

Hybrid Stents Based on Magnetic Hydrogels for Biomedical Applications

Tremendous attention has been given to hydrogels due to their mechanical and physical properties. Hydrogels are promising biomaterials due to their high biocompatibility. Magnetic hydrogels, which are based on hydrogel incorporated magnetic nanoparticles, have been proposed in biomedical applications. The advantages of magnetic hydrogels are that they can easily respond to externally applied magnetic fields and prevent the leakage of magnetic nanoparticles in the surrounding area. Herein, a prototype hybrid stent of magnetic hydrogel was fabricated, characterized, and evaluated for magnetic hyperthermia treatment. First, magnetic hydrogel was produced by a solution of alginate with magnetic nanoparticles in a bath of calcium chloride (5-15 mg mL^-1) in order to achieve the external gelation and optimize the heating rate. The increased concentration (1-8 mg mL^-1) of magnetic nanoparticles inside the hydrogel resulted in almost zero leakage of iron oxide nanoparticles after 15 days, guaranteeing that they can be used safely in biomedical applications. Thus, magnetic hybrid stents, which are based on the magnetic hydrogels, were developed in a simple way and were evaluated both in an agarose phantom model and in an ex vivo tissue sample at 30 mT and 765 kHz magnetic hyperthermia conditions to examine the heating efficiency. In both cases, hyperthermia results indicate excellent heat generation from the hybrid stent and facile temperature control via tuning magnetic nanoparticle concentration (2-8 mg mL^-1). This study can be a promising method that promotes spatially thermal distribution in cancer treatment or restenosis treatment of hollow organs.

Heating of an Aortic Stent for Coarctation Treatment During Magnetic Particle Imaging and Magnetic Resonance Imaging-A Comparative In Vitro Study

PURPOSE

To evaluate heating of a redilatable stent for the treatment of aortic coarctation in neonates and small children in the new imaging modality magnetic particle imaging and established magnetic resonance imaging.

MATERIALS AND METHODS

The cobalt-chromium stent (BabyStent, OSYPKA AG, Rheinfelden, Germany) has a stent design which allows for redilatation and adjustment of the diameter from 6 to 16 mm for a use in aortic coarctation. The stent loses its radial integrity while opening at predetermined breaking points at a diameter of 14 mm or 16 mm, respectively. We measured the temperature increase in the stent at different diameters during 7-min magnetic particle imaging and magnetic resonance imaging scans with fiber optic thermometers under static conditions surrounded by air. In magnetic particle imaging, stents with diameters from 6 to 16 mm were tested while in magnetic resonance imaging only stents with diameters of 6 mm and 14 mm were investigated exemplarily.

RESULT

In magnetic particle imaging, the measured temperature differences increased up to 4.7 K with growing diameters, whereas the opened stents with discontinuous struts at 14 and 16 mm showed only minimal heating of max. 0.5 K. In contrast to magnetic particle imaging, our measurements showed no heating of the stents during magnetic resonance imaging under identical conditions.

CONCLUSION

The BabyStent did show only slight heating in magnetic particle imaging and no detectable temperature increase in magnetic resonance imaging.

Health Care Monitoring and Treatment for Coronary Artery Diseases: Challenges and Issues

In-stent restenosis concerning the coronary artery refers to the blood clotting-caused re-narrowing of the blocked section of the artery, which is opened using a stent. The failure rate for stents is in the range of 10% to 15%, where they do not remain open, thereby leading to about 40% of the patients with stent implantations requiring repeat procedure within one year, despite increased risk factors and the administration of expensive medicines. Hence, today stent restenosis is a significant cause of deaths globally. Monitoring and treatment matter a lot when it comes to early diagnosis and treatment. A review of the present stent monitoring technology as well as the practical treatment for addressing stent restenosis was conducted. The problems and challenges associated with current stent monitoring technology were illustrated, along with its typical applications. Brief suggestions were given and the progress of stent implants was discussed. It was revealed that prime requisites are needed to achieve good quality implanted stent devices in terms of their size, reliability, etc. This review would positively prompt researchers to augment their efforts towards the expansion of healthcare systems. Lastly, the challenges and concerns associated with nurturing a healthcare system were deliberated with meaningful evaluations.

Wirelessly Heating Stents via Radiofrequency Resonance toward Enabling Endovascular Hyperthermia

Thermal therapy known as hyperthermia has served as an effective method for cancer treatment. This therapeutic approach has also been attracting attention for treatment of in-stent restenosis, the most common complication of stenting. Mild heating of stents has been shown to be a possible path to addressing this problem. Despite various studies on stent-based thermotherapy, this area still lacks a clinically viable method and technology. Here, a radiofrequency-powered "hot" stent prototype is reported in vitro and in vivo. An implantable stent device based on medical-grade stainless steel acts as an electrical resonator, or an efficient wireless heater operating only when resonated using tuned external electromagnetic fields. The system architecture uses a custom-developed power transmitter for wireless resonant powering/heating of the stent. An eight-shaped antenna is shown to be highly effective for near-field power transfer to the device and potentially to other smart implants, revealing stent heating efficiencies of up to 120 °C W^-1 , 206% of the level provided by a conventional loop antenna. Testing with swine models, the prototyped system achieves stent heating in blood flow by powering through air and skin tissue in vivo in a fully controlled manner. The results advance stent hyperthermia technology toward possible future clinical application.

A New RF Heating Strategy for Thermal Treatment of Atherosclerosis

OBJECTIVES

Restenosis remains a challenge for the treatment of atherosclerosis due to the damage of the endothelial layer and induced proliferation of the smooth muscle cell.

METHODS

A new RF heating strategy was proposed to selectively ablate the atherosclerosis plaque, and to thermally inhibit the proliferation of smooth muscle cells, while keeping the endothelial cells intact. To achieve the goal, an internal cooling agent and distributed electrodes have been integrated in the new designed balloon catheter to focus the shape conformal energy onto the plaque shape. A three-dimensional (3-D) model with experimentally fitted parameters has been established to demonstrate the heating ability of the design and evaluate the microelectrodes configurations for different plaque geometries.

RESULTS

The 3-D shape of the lesions resulting from different electrodes settings is obtained. It is found that by individual control of the micro-electrodes, special shapes of the lesions can be formed, which can match the eccentric crescent plaques. Besides, through changing of the polarity of the electrodes, separate lesions can be reached. This suggests the possibility for treatment of disconnected plaques in situ.

CONCLUSION

By the control of RF heating and convection coefficient of the internal cooling agent, a targeted heating region away from the inner surface of the blood vessel can be realized.

SIGNIFICANCE

This study has illustrated the possibility of achieving a precision thermal treatment of atherosclerosis in favor of inhibiting further restenosis.

Effects of hypothermia on the mechanical behavior of rabbit femoral arteries

The need to better understand the effects of non-physiological temperatures on arterial wall behavior is becoming more important because of the increased clinical use of hypothermal and hyperthermal treatments. The present study was performed to examine the effects of temperature on the mechanical behavior of femoral arteries excised from rabbits. Among 17, 27, 37, and 42°C, there were no significant differences in their diameter, stiffness, and P-D relations under the physiologically normal, control condition, although the arterial diameter was slightly smaller at 42°C than at the other three temperatures. Under the SMC-activated condition, on the other hand, we observed significant effects of temperature. For example, arterial diameter at 100mmHg was significantly larger at 17 and 27°C and smaller at 42°C compared with 37°C. Arterial stiffness at 40mmHg were significantly smaller at 17 and larger at 42°C than at 37°C, while the stiffness at 160mmHg were significantly larger at 17°C than at 37°C; however, there were no significant differences in the stiffness at 100mmHg among the four temperatures. Arterial contraction induced by SMC-activation was significantly different between 37°C and the other three temperatures; both of the maximum diameter response and diameter response at 100mmHg were significantly smaller at 17 and 27°C and larger at 42°C compared with 37°C. These results indicate that in the hypothermic range under the control condition, arteries are dilated when cooled, while they are constricted when heated. On the other hand, arterial response to SMC activation is significantly affected by the alterations of temperature. These results indicate that in the hypothermic range under the control condition, arteries are dilated when cooled, while they are constricted when heated. On the other hand, arterial response to the activation of vascular smooth muscle cells is significantly affected by the alteration of temperature. As the mechanical behavior of arterial wall is significantly influenced by temperature, this should be considered in the development of therapeutic methods and techniques for cardiovascular diseases.

Endothelial nitric oxide synthase induces heat shock protein HSPA6 (HSP70B') in human arterial smooth muscle cells

Endothelial nitric oxide synthase (eNOS) is the major source of nitric oxide (NO) production in blood vessels. One of the pleitropic functions of eNOS derived NO is to inhibit vascular smooth muscle cell proliferation in the blood vessel wall, and whose dysfunction is a primary cause of atherosclerosis and restenosis. In this study there was an interest in examining the gene profile of eNOS adenoviral (Ad-eNOS) transduced human coronary artery smooth muscle cells (HCASMC) to further understand the eNOS inhibitory effect on smooth muscle cell proliferation. To this aim a whole genome wide analysis of eNOS transduced HCASMCs was performed. A total of 19 genes were up regulated, and 31 genes down regulated in Ad-eNOS transduced HCASMCs compared to cells treated with an empty adenovirus. Noticeably, a cluster of HSP70 gene family members was amongst the genes up regulated. Quantitative PCR confirmed that transcripts for HSPA1A (HSP70A), HSPA1B (HSP70B) and HSPA6 (HSP70B') were elevated 2, 1.7 and 14-fold respectively in Ad-eNOS treated cells. The novel gene HSPA6 was further explored as a potential mediator of eNOS signaling in HCASMC. Immunoblotting showed that HSPA6 protein was induced by Ade-NOS. To functionally examine the effect of HSPA6 on SMCs, an adenovirus harboring the HSPA6 gene under the control of a constitutive promoter was generated. Transduction of HCASMCs with Ad-HSPA6 inhibited SMC proliferation at 3 and 6 days post serum growth stimulation, and paralleled the Ad-eNOS inhibition of SMC growth. The identification in this study that HSPA6 overexpression inhibits SMC proliferation coupled with the recent finding that inhibition of HSP90 has a similar effect, progresses the field of targeting HSPs for vascular repair.

In vitro study on the feasibility of magnetic stent hyperthermia for the treatment of cardiovascular restenosis

Thermal treatment or hyperthermia has received considerable attention in recent years due to its high efficiency, safety and relatively few side-effects. In this study, we investigated whether it was possible to utilize targeted thermal or instent thermal treatments for the treatment of restenosis following percutaneous transluminal coronary angioplasty (PTCA) through magnetic stent hyperthermia (MSH). A 316L stainless steel stent and rabbit vascular smooth muscle cells (VSMCs) were used in the present study, in which the inductive heating characteristics of the stent under alternative magnetic field (AMF) exposure, as well as the effect of MSH on the proliferation, apoptosis, cell cycle and proliferating cell nuclear antigen (PCNA) expression of the rabbit VSMCs, were evaluated. The results demonstrated that 316L stainless steel coronary stents possess ideal inductive heating characteristics under 300 kHz AMF exposure. The heating properties were shown to be affected by the field intensity of the AMF, as well as the orientation the stent axis. MSH had a significant effect on the proliferation and apoptosis of VSMCs, and the effect was temperature-dependent. While a mild temperature of 43°C demonstrated negligible effects on the growth of VSMCs, MSH treatment above 47°C effectively inhibited the VSMC proliferation and induced apoptosis. Furthermore, a 47°C treatment exhibited a significant and long-term inhibitory effect on VSMC migration. The results strongly suggested that MSH may be potentially applied in the clinic as an alternative approach for the prevention and treatment of restenosis.

Freeze-thaw induced biomechanical changes in arteries: role of collagen matrix and smooth muscle cells

Applications involving freeze-thaw, such as cryoplasty or cryopreservation can significantly alter artery biomechanics including an increase in physiological elastic modulus. Since artery biomechanics plays a significant role in hemodynamics, it is important to understand the mechanisms underlying these changes to be able to help control the biomechanical outcome post-treatments. Understanding of these mechanisms requires investigation of the freeze-thaw effect on arterial components (collagen, smooth muscle cells or SMCs), as well as the components' contribution to the overall artery biomechanics. To do this, isolated fresh swine arteries were subjected to thermal (freeze-thaw to -20 degrees C for 2 min or hyperthermia to 43 degrees C for 2 h) and osmotic (0.1-0.2 M mannitol) treatments; these treatments preferentially altered either the collagen matrix (hydration/stability) or smooth muscle cells (SMCs), respectively. Tissue dehydration, thermal stability and SMC functional changes were assessed from bulk weight measurements, analyses of the thermal denaturation profiles using Fourier transform infrared (FTIR) spectroscopy and in vitro arterial contraction/relaxation responses to norepinephrine (NE) and acetylcholine (AC), respectively. Additionally, Second Harmonic Generation (SHG) microscopy was performed on fresh and frozen-thawed arteries to directly visualize the changes in collagen matrix following freeze-thaw. Finally, the overall artery biomechanics was studied by assessing responses to uniaxial tensile testing. Freeze-thaw of arteries caused: (a) tissue dehydration (15% weight reduction), (b) increase in thermal stability (approximately 6.4 degrees C increase in denaturation onset temperature), (c) altered matrix arrangement observed using SHG and d) complete SMC destruction. While hyperthermia treatment also caused complete SMC destruction, no tissue dehydration was observed. On the other hand, while 0.2 M mannitol treatment significantly increased the thermal stability (approximately 4.8 degrees C increase in denaturation onset), 0.1 M mannitol treatment did not result in any significant change. Both 0.1 and 0.2 M treatments caused no change in SMC function. Finally, freeze-thaw (506+/-159 kPa), hyperthermia (268+/-132 kPa) and 0.2 M mannitol (304+/-125 kPa) treatments all caused significant increase in the physiological elastic modulus (Eartery) compared to control (185+/-92 kPa) with the freeze-thaw resulting in the highest modulus. These studies suggest that changes in collagen matrix arrangement due to dehydration as well as SMC destruction occurring during freeze-thaw are important mechanisms of freeze-thaw induced biomechanical changes.

Deficiency of clusterin inhibits neointimal hyperplasia after vascular injury

AIM

Increased clusterin mRNA and protein levels have been detected in various tissues undergoing stress, and we previously reported that clusterin is markedly induced in media and neointima following vascular injury. The present study therefore investigated the impact of clusterin on neointimal hyperplasia following vascular injury.

METHODS AND RESULTS

As compared with wild-type mice, clusterin knockout mice (clusterin-KO) demonstrated a significant decrease of the intima/media ratio 4 weeks after cuff placement. Immunohistochemical analysis of injured femoral arteries in clusterin-KO demonstrated the accumulation of p53 in nuclei of neointimal vascular smooth muscle cells (VSMCs). Moreover, VSMCs from either clusterin-KO or rat VSMCs treated with clusterin-short-interfering (si) RNA subjected to static stretch exhibited significantly increased p53 and p21, and increased G1 cell cycle arrest as indicated by flow cytometry compared with VSMCs from wild-type mice.

CONCLUSION

Reduced clusterin expression reduced the proliferation of VSMCs and induced G1 arrest via p53 and p21. Clusterin therefore represents a promising molecular target to limit restenosis after coronary intervention.

NF-κB regulates the response of embryonic cells to heat shock

NF-kappaB was shown previously to regulate apoptotic cell death processes in various experimental systems. However, its role in controlling teratogen-induced cell death has not been established yet. Therefore, the objective of the present study was to explore the involvement of the p65 subunit of NF-kappaB in the response of mouse embryonic fibroblasts (MEFs) to heat shock, using p65 knockout (p65-/-) cells. Indeed, we found p65-/- MEFs to be more susceptible to the exposure to heat shock, as compared with wild-type (WT) MEFs, as they demonstrated a more prominent decrease in cell survival and proliferation as well as the appearance of cells undergoing apoptotic cell death. These heat-shock-induced effects were preceded by a decrease in p65 expression in WT cells, which was accompanied by a decrease in IkappaBalpha expression in WT MEFs, while disappearing completely in p65-/- MEFs and accordingly, by an increase in p-IkappaBalpha expression in both cell lines, which was found to be more prominent in p65-/- MEFs. Interestingly, the heat shock-induced decrease in p65 expression was accompanied by an increase in HSP70 expression in both cell lines. However, it was again found to be more prominent in p65-/- MEFs. Taken together, our results suggest a protective role for the p65 subunit of NF-kappaB in mechanisms underlying the response of embryonic cells to heat shock.

Expression of lectin-like oxidized LDL receptor-1 in smooth muscle cells after vascular injury

Lectin-like oxidized LDL receptor-1 (LOX-1) is an oxidized LDL receptor, and its role in restenosis after angioplasty remains unknown. We used a balloon-injury model of rabbit aorta, and reverse transcription-polymerase chain reaction revealed that LOX-1 mRNA expression was modest in the non-injured aorta, reached a peak level 2 days after injury, and remained elevated until 24 weeks after injury. Immunohistochemistry and in situ hybridization showed that LOX-1 was not detected in the media of non-injured aorta but expressed in both medial and neointimal smooth muscle cells (SMC) at 2 and 24 weeks after injury. Low concentrations of ox-LDL (10 microg/mL) stimulated the cultured SMC proliferation, which was inhibited by antisense oligonucleotides of LOX-1 mRNA. Double immunofluorescence staining showed the colocalization of LOX-1 and proliferating cell nuclear antigen in human restenotic lesion. These results suggest that LOX-1 mediates ox-LDL-induced SMC proliferation and plays a role in neointimal formation after vascular injury.

Repeated Thermal Therapy Up-Regulates Endothelial Nitric Oxide Synthase and Augments Angiogenesis in a Mouse Model of Hindlimb Ischemia

BACKGROUND

Nitric oxide (NO), constitutively produced by endothelial NO synthase (eNOS), plays roles in angiogenesis. Having reported that thermal therapy up-regulated the expression of arterial eNOS in hamsters, we investigated whether this therapy increased angiogenesis in mice with hindlimb ischemia.

METHODS AND RESULTS

Unilateral hindlimb ischemia was induced in apolipoprotein E-deficient mice, which were divided into control and thermal therapy groups. The latter mice were placed in a far-infrared dry sauna at 41 degrees C for 15 min and then at 34 degrees C for 20 min once daily for 5 weeks. Laser Doppler perfusion imaging demonstrated that the ischemic limb/normal side blood perfusion ratio in the thermal therapy group was significantly increased beyond that in controls (0.79+/-0.04 vs 0.54+/-0.08, p<0.001). Significantly greater capillary density was seen in thermal therapy group (757+/-123 /mm2 vs 416+/-20 /mm2, p<0.01). Western blotting showed thermal therapy markedly increased hindlimb eNOS expression. To study possible involvement of eNOS in thermally induced angiogenesis, thermal therapy was given to mice with hindlimb ischemia with or without N(G)-nitro-L-arginine methyl ester (L-NAME) administration for 5 weeks. L-NAME treatment eliminated angiogenesis induced using thermal therapy. Thermal therapy did not increase angiogenesis in eNOS-deficient mice.

CONCLUSION

Angiogenesis was induced via eNOS using thermal therapy in mice with hindlimb ischemia.

Thermomechanical behavior of human carotid arteries in the passive state

Localized heating or cooling is expanding the clinical procedures used to treat cardiovascular diseases. Advantageous implementation and development of these methods are linked indissolubly to a deeper understanding of the arterial response to combined mechanical and thermal loads. Despite this, the basic thermomechanical behavior of human blood vessels still remains largely unknown, primarily due to the lack of appropriate experimental data. In this work, the influence of temperature on the passive behavior of human carotid arteries was studied in vitro by means of inflation tests. Eleven carotid segments were tested in the range 0–200 mmHg at four different temperatures of 17, 27, 37, and 42°C. The results show that the combined change of temperature and stress has a dramatic effect on the dilatation coefficient of the arterial wall, which is shifted from negative to positive depending on the stress state, whereas the structural stiffness of the arterial wall does not change appreciably in the range of temperatures tested.

Thermal treatment attenuates neointimal thickening with enhanced expression of heat-shock protein 72 and suppression of oxidative stress

BACKGROUND

The beneficial effects of thermal therapy have been reported in several cardiovascular diseases. However, it is unknown whether the thermal treatment has some beneficial roles against the development of atherosclerosis.

METHODS AND RESULTS

The inflammatory arterial lesion was introduced by placement of a polyethylene cuff on femoral arteries of male Sprague-Dawley rats for 4 weeks. Thermal-treated group underwent daily bathing in 41 degrees C hot water for 15 minutes. Neointimal thickening along with immunohistochemical expression of heat-shock proteins (HSPs), monocyte chemoattractant protein-1 (MCP-1), and NADPH oxidase were compared with those of a thermally untreated (Control) group. Morphometric analysis demonstrated a significant suppression of neointimal thickening in thermal-treated group compared with the Control group (intimal/medial area ratios, 0.01+/-0.01 versus 0.31+/-0.04, P<0.01). Expression of MCP-1 and infiltration of ED-positive cells were enhanced in the adventitial layer of Control. More importantly, expression of HSP72 in media was enhanced by thermal treatment. Expression of p22-phox, the major membrane subunit of NADPH oxidase, and MCP-1 was augmented in cuff-injured adventitia of the Control but not the thermal-treated groups.

CONCLUSIONS

Thermal treatment significantly attenuated infiltration of inflammatory cells in adventitia and suppressed neointimal thickening in cuff-injured arteries with the enhancement of HSP72 expression and suppression of oxidative stress.

HTLV-I Tax protein inhibits apoptosis induction but not G1 arrest by pyrrolidinedithiocarbamate, an anti-oxidant, in adult T cell leukemia cells

OBJECTIVE

We examined the anti-tumor effect of pyrrolidinedithiocarbamate (PDTC) on HTLV-1-infected T clones and the mechanism of HTLV-1 Tax protein inhibition of PDTC-induced apoptosis.

MATERIALS AND METHODS

Tax-nonproducing clones S1T and Su9T01, Tax-producing clones K3T and F6T, and Tax cDNA stably transfected S1TcTax clones S1TcTax04 and S1TcTax05 were examined for PDTC inhibition of thymidine incorporation and apoptosis induction by ISEL method. In addition, S1TcTax clones were analyzed by DNA histography and DNA fragmentation and also examined for p53, p21, or Bax protein expression by Western blot.

RESULTS

PDTC inhibited thymidine incorporation of all four HTLV-1-infected T cells in a similar dose-dependent manner, but K3T and F6T were more resistant than S1T and Su9T01 in apoptosis induction. S1TcTax clones also showed resistance to PDTC-induced apoptosis as compared to Tax-nonproducing S1T and S1Tneo. DNA histography demonstrated that PDTC induces G1 arrest and apoptosis in S1T and S1Tneo, and that S1TcTax clones are also sensitive to PDTC in G1 arrest but resistant in apoptosis induction. DNA fragmentation also demonstrated ladder formation only in S1Tneo but not in S1TcTax04. Western blots demonstrated higher expression of p53 and p21 proteins in S1Tneo than in S1TcTax04 during whole phase after PDTC stimulation with moderate enhancement in S1Tneo but small in S1TcTax04. Bax protein expression was detected only at early phase in S1Tneo but was not detected in S1TcTax04.

CONCLUSION

These findings suggest that PDTC-induced apoptosis is related with Bax, and that G1 arrest is possibly related with p21. Tax might inhibit apoptosis induction mainly via inhibition of Bax expression preceded at least in part by p53 inhibition.

Heat induced HSP20 phosphorylation without increased cyclic nucleotide levels in swine carotid media

BACKGROUND

Heat pretreatment of swine carotid artery has been shown to increase ser16-heat shock protein 20 (HSP20) phosphorylation and suppress force, i.e., reduce force with only minimal reduction in ser19-myosin regulatory light chain (MRLC) phosphorylation.

RESULTS

We further investigated this response in intact histamine stimulated swine carotid artery rings. There was a heat threshold such that increased ser16-HSP20 phosphorylation and force suppression were observed between 43 degrees C and 46 degrees C. The increased ser16-HSP20 phosphorylation persisted up to 16 hours after 44.5 degrees C heat treatment. Pretreatment of swine carotid media at 44.5 degrees C increased ser16-HSP20 phosphorylation without increases in [cAMP] or [cGMP], suggesting an alternate mechanism, perhaps phosphatase inhibition, for the increase in ser16-HSP20 phosphorylation. Heat pretreatment at 47.5 degrees C reduced force by decreasing MRLC phosphorylation rather than by large increases in ser16-HSP20 phosphorylation. HSP20 phosphorylation at the putative PKC site did not change with any treatment.

CONCLUSION

These results demonstrate that multiple mechanisms can induce force suppression that is correlated with ser16-HSP20 phosphorylation: 1) nitrovasodilators via cGMP, 2) forskolin via cAMP, and 2) thermal stress in a cyclic nucleotide independent manner.