[YAP regulates the proliferation and modifies the sensitivity to sorafenib in hepatocellular carcinoma cells]

Objective: To detect the expression level of YES-associated protein 1 (YAP) in hepatocellular carcinoma (HCC) cell lines and investigate its effects on the proliferation activity and the sensitivity to sorafenib in HCC cells. Methods: Western blot was used to detect the protein expression levels of YAP in SMMC-7721, SK-Hep-1, HepG-2, Huh7 and the normal liver cell line L-O2. YAP specific small interfering RNA (si-YAP) or YAP expression plasmid were transfected in SK-Hep-1 or Huh7 cells, respectively. Cell counting kit-8 (CCK-8) test was used to detect the cell proliferation activity and the cell cycle test was conducted by flow cytometry. SK-Hep-1 and SK-Hep-1 si-YAP cells were subcutaneously injected into the nude mice which were sequentially treated by intragastric administration of sorafenib, and the tumor growth in vivo were observed and compared. Results: The expression of YAP was upregulated in HCC cell lines. Deletion of YAP expression significantly decreased the survival rate of SK-Hep-1 cells [(78.5±0.3)% vs (92.3±0.2)%, P=0.025]. Knockdown of YAP significantly increased the percentage of G(0)/G(1)-phase cells [ (65.4±3.3) % vs (55.7±3.4) %, P=0.039]. On the contrary, upregulation of the YAP expression in Huh7 cells significantly increased the cell survival rate [(81.2±1.3)% vs (62.5±1.1)%, P=0.013] and reduced the percentage of G(0)/G(1)-phase cells [(38.2±3.8)% vs (48.8±2.9)%, P=0.019]. The survival rate of SK-Hep-1 cells treated by si-YAP combined with sorafenib was (31.13±1.79)%, significantly lower than (48.87±0.58) % of SK-Hep-1 cells treated by sorafenib alone (P=0.001), while overexpression of YAP attenuated the inhibitory effect of sorafenib on the survival of Huh7 cells [(69.98±2.94) % vs (53.53±1.93)%, P=0.001]. The tumor weights of SK-Hep-1 group, sorafenib alone group, SK-Hep-1 si-YAP group and SK-Hep-1 si-YAP combined with sorafenib group were (0.96±0.08) g, (0.62±0.08) g, (0.70±0.06) g and (0.27±0.02) g, respectively. The tumor weights of sorafenib alone group and SK-Hep-1 si-YAP group were significantly lower than that of SK-Hep-1 group (P=0.012 and P=0.031, respectively). The tumor weight of SK-Hep-1 si-YAP combined with sorafenib group was significantly lower than that of SK-Hep-1 si-YAP group (P=0.001). Conclusions: The expression of YAP is upregulated in HCC cell lines, which regulates the proliferation, cell cycle, and sensitivity to sorafenib of HCC cells. YAP is a potential molecular target for HCC treatment.

Simulation study of the effects of hypovolaemia on cardiovascular response to orthostatic stress

To investigate the role played by hypovolaemia in the mechanism of orthostatic intolerance, a mathematical model was developed. The model consisted of seven sub-models that describe: the redistribution of blood induced by lower body negative pressure (LBNP); filling of the left ventricle; contracting of the left ventricle; interaction between the left ventricle and peripheral circulation; and baroreflex regulation. The model was evaluated using experimental data. Using the model, computer simulations were performed to investigate the effects of hypovolaemia on the cardiovascular response to LBNP. The simulation results indicated that, first, when the blood loss is less than 5%, blood pressure can be maintained in the normal range by the baroreflex regulatory mechanism, even with high LBNP application; secondly, when the blood loss is between 15 and 20%, heart rate and blood pressure can be kept in the normal range if LBNP is not applied, but blood pressure falls sharply with LBNP application; and, thirdly, when the blood loss is 25%, the cardiovascular system is in an unstable state (heart rate: 116 beat min (-1), systolic blood pressure: 97 mmHg; diastolic blood pressure: 77 mmHg), even without any LBNP, and becomes more unstable with LBNP. The simulation results support the hypothesis that hypovolaemia is a cause of orthostatic intolerance.

[A biomechanical model of left ventricle regional ischemia: a computer simulation]

Objective. To analyze the biomechanical mechanism of left ventricular regional ischemia and to investigate the changes of myocardial contractilities in different ventricular regions during regional ischemia. Method. A time-dependent mathematical model for simulating left ventricle regional ischemia has been developed basing on geometry of left ventricle, spatial angle distribution, propagation of electrical activation signals and biomechanical properties of cardiac muscle fibers. Then the model was incorporated into a multi-element circulatory model established by us previously. By using this model, some simulation experiments relating myocardium contractility to regional ischemia in inner or outer layers of ventricular wall were performed. Result. Myocardial contractility of the ischemic layers decreased whereas that of normal layers increased significantly. Compared with ischemia in outer layers of ventricular wall, ischemia in inner layers of ventricular wall had more effects upon cardiac function. Conclusion. The myocardium of normal region had the ability to increase its contractility in order to maintain a normal cardiac function. A method to simulate the relationship between cardiovascular function and left ventricular regional ischemia was developed.

[A simulation study of effects of depressed myocardial contractility on cardiovascular response to lower body negative pressure]

OBJECTIVE

To study the effects of depressed myocardial contractility induced by microgravity on cardiovascular response to orthostatic stress, and to investigate the role played by the changes of myocardial contractility in the mechanism of cardiovascular deconditioning and orthostatic intolerance induced by space weightlessness.

METHOD

On the basis of our previous model used to simulate the cardiovascular response to lower body negative pressure (LBNP), the factor of changes of myocardial contractility was incorporated into the model by multiplying a coefficient to the maximum elastance of the heart working sub-model. By decreasing the coefficient progressively, then the changes of heart rate (HR), blood pressure (BP), and cardiac output (CO) during LBNP after 0 - 30% of myocardial contractility depression combined with 12% decrease of total blood volume were simulated.

RESULT

Simulation results indicated that depressed myocardial contractility induces more augment of HR, and more decrease of BP and CO during LBNP.

CONCLUSION

The depression of myocardial contractility degenerated cardiovascular response to orthostatic stress.

[Changes of cerebral blood flow during 21 d head-down tilt bed rest and the effect of lower body negative pressure during the last week]

Objective. To investigate the changes of cerebral blood flow (CBF) during 21 d head-down tilt (HDT) bed rest and the effect of lower body negative pressure (LBNP) in the last week. Method. Twelve healthy male subjects were randomly divided into control and LBNP groups, with 6 in each group. All of them were exposed to -6 degrees HDT for 21 d. The LBNP group received -4.0 kPa LBNP training 1 h/d in the last week of HDT while the control group did not. CBF and cerebral vascular resistance were measured by rheoencephalogram in pre-HDT, day 3, 10 and 21 of HDT. Result. In control group, left cerebral I quadrant area and inrush velocity decreased significantly during HDT, and left cerebral delta Gy wave crest height decreased significantly, whereas left cerebral resistance index increased significantly on day 3 and 21 of HDT as compared to those of pre-HDT. In LBNP group, left cerebral I quadrant area decreased significantly, and left cerebral delta Gy wave crest height and inrush velocity tended to decrease on day 3 and 21 of HDT, whereas left cerebral resistance index increased significantly during HDT as compared to those of pre-HDT. There were no significant differences between above indexes in control group and LBNP group. Conclusion. It is suggested that 21 d HDT may increase cerebral vascular resistance and decrease CBF, which can not be prevented by LBNP training in the last week of 21 d HDT.

[Changes of cardiac function during 21 d head-down tilt bed rest and the effect of lower body negative pressure in the last week]

OBJECTIVE

To investigate the change of cardiac function during 21 d head-down tilt (HDT) bed rest and the effect of lower body negative pressure (LBNP) in the last week in human.

METHOD

12 healthy male served as subjects which were randomly divided into control and LBNP groups, with 6 in each group. All of them were exposed to -6 degrees HDT for 21 d. The LBNP group received -4.0 kPa LBNP training 1 h/d in the last week of the test. The cardiac pump function and cardiac systole function were measured before, during and after HDT.

RESULT

Cardiac output, cardiac index and stroke volume decreased significantly, whereas total peripheral resistance, pre-ejection period (PEP), isovolumetric contraction time/left ventricular ejection time (LVET) and PEP/LVET increased significantly during HDT in both control and LBNP groups, compared to pre-HDT values, and they returned to normal level on day 2 post HDT. PEP and PEP/LVET in LBNP group were significantly higher than those in control group on day 21 of HDT and day 2 post HDT.

CONCLUSION

The reduction of cardiac pump function and cardiac systole function induced by 21 d HDT could not be prevented by LBNP training in the last week of 21 d HDT.

Effects of depressed myocardial contractility induced by microgravity on cardiovascular response to orthostatic stress: a computer simulation

The aim of present study is to investigate the role played by the depression of myocardial contractility in the mechanism of cardiovascular deconditioning and orthostatic intolerance (OI) induced by space weightlessness. Based on our previous model, which was used to simulate cardiovascular response to lower body negative pressure (LBNP), we incorporated the factor of changes of myocardial contractility into the model by multiplying a coefficient to the time-varying elastance that represents the changes of cardiac contractility. By decreasing the coefficient progressively, we simulated the changes of heart rate (HR), blood pressure (BP), and cardiac output (CO) during LBNP after 0-30% of myocardial contractility depression combined with 12% decrease of the total blood volume. Simulation results indicate that depressed myocardial contractility induces more augment of HR, and more decrement of BP and CO during LBNP and suggest that the depression of myocardial contractility degenerate cardiovascular response to orthostatic stress.

[A simulated study of effects of simulated hypovolemia on cardiovascular response to orthostatic stress]

Objective. To study the effects of hypovolemia on cardiovascular response to orthostatic stress, and to investigate the role of hypovolemia in the mechanism of cardiovascular deconditioning and orthostatic intolerance induced by space weightlessness. Method. The effects of loss of blood volume had been incorporated in the sub-model of blood redistribution in the model developed for simulating the cardiovascular response to lower body negative pressure (LBNP). With the help of the model, we simulated the changes of heart rate (HR) and blood pressure (BP) during LBNP after 0-25% loss of blood volume. Result. When the amount of decrease of blood volume was less than 5% of the total blood volume, HR and BP could be maintained in normal range during LBNP through baroreflex regulation. When the amount of the decrease of blood volume was more than 15% of the total blood volume, HR and BP could be kept in normal range when the subject was supine and at rest. But BP fell sharply and the cardiovascular system almost collapsed during orthostatic exposure. Conclusion. Decrease of blood volume causes significant degradations of cardiovascular response to orthostatic stress.

Cardiovascular peripheral effector mechanism in postflight orthostatic intolerance: a simulation study

Orthostatic intolerance (OI) following exposure to microgravity or head-down bed rest is frequently observed and is thought to be multifactorial origin. Although hypovolemia is considered as the primary cause of OI, the role played by other factors, such as the lowered vasoconstrictor responsiveness (VCR) of resistance vessels, the enhanced vasoconstriction response of cerebral vessels, and the depressed myocardial contractility need to be elucidated. It is difficult to assess experimentally how each of these changes would affect orthostatic tolerance and how these factors interact with each other. An alternative approach is to conduct simulation studies by use of mathematical models of cardiovascular system (CVS) capable of simulating the CVS response to orthostatic stress. This presentation describes the construction of the model used, and presents the preliminary simulation results illustrating the effects of varying individually the level of hypovolemia, VCR of the resistance vessels in lower limbs and abdominal viscera, VCR of the brain vessels or myocardial contractility on responses to orthostatic stress. The ultimate goal of our work was to integrate the new experimental findings and to simulate the complexity to get a thorough understanding of the mechanism of postflight cardiovascular dysfunction and orthostatic intolerance.

[Effects of 24 h -6 degrees head-down tilt bed-rest on cardiovascular function and response to orthostatic stress]

Objective. To investigate the effects of 24 h -6 degrees head-down tilt bed-rest (HDT) on cardiovascular function and response to orthostatic stress. Method. -6 degrees head-down tilt bed rest for 24 h in 6 healthy males, aged 22-23, were observed. The changes of cardiac function were observed by electrical impedance instrument before and at 0th, 6th, 12th, 18th and 24th hour of HDT, and blood pressure were recorded and urine were collected. The changes of cardiovascular response to head up tilt (HUT 90 degrees, 10 min) before and post HDT were recorded. Result. During HDT, HR reduced significantly than that of pre-HDT (standing). HR at 6th, 12th, and 18th hour of HDT reduced significantly than that at 0th hour of HDT. Stroke output (SO) and stroke index (SI) [correction of CI] at 0th, 6th, 12th, and 24th hour of HDT were higher than pre-HDT value. Cardiac output (CO) and cardiac index (CI) at 18th hour of HDT were significantly lower than those at 0 h of HDT. Total peripheral resistance (TPR) at 18th hour of HDT were higher than that at 0th of HDT. During HUT before and post HDT, HR, MBP, TPR were significantly increased, SO, [correction of SV] SI, CO and CI were significantly reduced. DBP were significantly increased and PP were reduced significantly during HUT post-HDT. Hourly average value of urine during 0-4 h were higher than those during 4-12 h and 12-24 h. Conclusion. 24 h -6 degrees head-down tilt bed rest has significant effects on cardiovascular function and response to HUT in humans.

[Computer simulation of cardiovascular response to lower body negative pressure]

OBJECTIVE

To simulate the cardiovascular response to lower body negative pressure (LBNP).

METHOD

A computer model was developed. It had 7 subparts: the redistribution of blood, the filling of left ventricle, left ventricle, peripheral circulation, control of heart rate, control of peripheral resistance and control of venous tone. The heart rate and venous tone were controlled by high-pressure receptor baroreflex, while the peripheral resistance was controlled by high- and low-pressure receptor baroreflexes.

RESULT

With the help of the model, cardiovascular response to LBNP up to -10.64 kPa (-80 mmHg) were simulated, including the changes of systolic blood pressure, mean blood pressure, heart rate and cardiac output. The time-dependent response to a LBNP profile was also simulated. The simulation results coincided well with human experiments.

CONCLUSION

The model is valid and can accurately reproduce the short-term hemodynamic response to LBNP.

[Countermeasuring effect of lower body negative pressure against orthostatic intolerance induced by 21 d -6 degrees head down tilt in humans]

Objective. To investigate whether LBNP during 21 d -6 degrees head-down tilt (HDT) would modify orthostatic tolerance. Method. 12 healthy males, age 23.7 +/- 5.0, were exposed to -6 degrees HDT for 21 d. 6 of them received -4.0 kPa LBNP sessions for 1 h/d from 15th day to 21st day of HDT. The other 6 served as control. HUT + 75 degrees, 20 min orthostatic tolerance test were done before, on day 10 and on day 21 of HDT. Result. During HUT + 75 degrees, 20 min orthostatic tolerance test on day 10 of HDT, 5 subjects of the control group and 4 of the LBNP group presented presyncopal or syncopal signs and symptoms, the average standing time of both groups were shorter than those of the pre-HDT (p<0.05). During HUT + 75 degrees, 20 min orthostatic tolerance test on day 21 of HDT, 5 subjects of the control group and one subject of the LBNP group presented presyncopal or syncopal signs and symptoms, the average standing time of control group reduced significantly as compared with those of pre-HDT(P<0.05), also significantly shorter than those of LBNP group (P<0.05). Conclusion. The present study clearly shows that the use of LBNP could alleviate the bed rest-induced orthostatic intolerance.