Decreased intracellular [Ca2+ ] coincides with reduced expression of Dhprα1s, RyR1, and diaphragmatic dysfunction in a rat model of sepsis.

INTRODUCTION: Sepsis can cause decreased diaphragmatic contractility. Intracellular calcium as a second messenger is central to diaphragmatic contractility. However, changes in intracellular calcium concentration ([Ca2+ ]) and the distribution and co-localization of relevant calcium channels [dihydropyridine receptors, (DHPRα1s) and ryanodine receptors (RyR1)] remain unclear during sepsis. In this study we investigated the effect of changed intracellular [Ca2+ ] and expression and distribution of DHPRα1s and RyR1 on diaphragm function during sepsis. METHODS: We measured diaphragm contractility and isolated diaphragm muscle cells in a rat model of sepsis. The distribution and co-localization of DHPRα1s and RyR1 were determined using immunohistochemistry and immunofluorescence, whereas intracellular [Ca2+ ] was measured by confocal microscopy and fluorescence spectrophotometry. RESULTS: Septic rat diaphragm contractility, expression of DHPRα1s and RyR1, and intracellular [Ca2+ ] were significantly decreased in the rat sepsis model compared with controls. DISCUSSION: Decreased intracellular [Ca2+ ] coincides with diaphragmatic contractility and decreased expression of DHPRα1s and RyR1 in sepsis. Muscle Nerve 56: 1128-1136, 2017.

High levels of positive end-expiratory pressure preserve diaphragmatic contractility during acute respiratory distress syndrome in rats.

NEW FINDINGS: What is the central question of this study? Higher levels of positive end-expiratory pressure (PEEP) have recently been used in patients with acute respiratory distress syndrome (ARDS). In normal physiological conditions, the ability of the diaphragm to generate pressure is reduced when the lung volume is elevated beyond its functional residual capacity. It is unknown whether higher levels of PEEP will have a negative impact on diaphragmatic contraction in the presence of the pathophysiology of ARDS. What is the main finding and its importance? Mechanical ventilation with higher levels of PEEP reduced lung injury, improved diaphragmatic contractility and increased the expression of both dihydropyridine receptor and ryanodine receptor in the diaphragms of rats with ARDS. Higher levels of positive end-expiratory pressure (PEEP) have recently been used in patients with acute respiratory distress syndrome (ARDS). In normal physiological conditions, the ability of the diaphragm to generate pressure is reduced when the lung volume is elevated beyond its functional residual capacity. Thus, it is critical to understand whether higher levels of PEEP will have a negative impact on diaphragmatic contraction in the presence of the pathophysiology of ARDS. This study was designed to determine whether higher levels of PEEP reduce diaphragmatic contractility in a rat model of ARDS generated using i.p. lipopolysaccharide. Forty rats were randomly assigned to the following five groups: a control group with no special treatment; an ARDS group with no mechanical ventilation; and three ARDS groups with mechanical ventilation with PEEP at 0, 5 or 10 cmH2 O, respectively. We found that mechanical ventilation with PEEP reduced lung injury, improved diaphragmatic contractility and increased the expression of both dihydropyridine receptor and ryanodine receptor in the diaphragms of rats with ARDS. These changes were most significant at a PEEP of 10 cmH2 O among all applied levels of PEEP. In conclusion, using a rat ARDS model, this study confirmed that diaphragmatic contractility was preserved by mechanical ventilation with high levels of PEEP.

Reduced DHPRα1S and RyR1 expression levels are associated with diaphragm contractile dysfunction during sepsis.

INTRODUCTION: Sepsis often causes diaphragm contractile dysfunction. Dihydropyridine receptors (DHPRα1s and DHPRα1c) and ryanodine receptors (RyR1, RyR2, and RyR3) are essential for excitation-contraction coupling in striated muscles. However, their expression in diaphragm during sepsis have not been explored. METHODS: Eight rats received endotoxin, and 8 more rats received placebo. After 24 hours, 3) diaphragm isometric contractile force was measured. The mRNA and protein levels of DHPRs and RyRs in diaphragm muscles were determined. RESULTS: Sepsis weakened diaphragm contractile function. The expression levels of DHPRα1s and RyR1 were significantly lower in septic rats than in control rats. The expression levels of DHPRα1c and RyR3 were unaffected by sepsis. RyR2 was undetectable at both mRNA and protein levels in the control and sepsis groups. CONCLUSIONS: Weakened diaphragm contraction in the septic rats was associated with reduced mRNA and protein expression of DHPRα1s and RyR1, the isoforms of skeletal muscles.

Combined anticancer activity of osthole and cisplatin in NCI-H460 lung cancer cells in vitro.

Drug combination therapies are common practice in the treatment of cancer. Cisplatin is the most active chemotherapeutic agent for lung cancer treatment. Osthole is a natural compound extracted from a number of medicinal plants. To determine whether osthole enhances the anticancer effect of cisplatin in human lung cancer, we treated NCI-H460 cells with osthole alone or in combination with cisplatin and evaluated cell growth and apoptosis using 3-(4,5-dimethyl thiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry and fluorescence microscopy. The results showed that, in comparison with single agent treatment, the combination of osthole and cisplatin resulted in greater efficacy in growth inhibition and apoptosis induction. Western blot analysis revealed that the combination effect of osthole and cisplatin was due to regulation of the Bcl-2 family proteins. Findings of this investigation suggested that osthole combined with cisplatin is a potential clinical chemotherapeutic approach in human lung cancer.

Interactive effects of corticosteroid and mechanical ventilation on diaphragm muscle function.

Information on the interactive effects of methylprednisolone, controlled mechanical ventilation (CMV), and assisted mechanical ventilation (AMV) on diaphragm function is sparse. Sedated rabbits received 2 days of CMV, AMV, and spontaneous breathing (SB), with either methylprednisolone (MP; 60 mg/kg/day intravenously) or saline. There was also a control group. In vitro diaphragm force, myofibril ultrastructure, αII-spectrin proteins, insulin-like growth factor-1 (IGF-1), and muscle atrophy F-box (MAF-box) mRNA were measured. Maximal tetanic tension (P(o)) decreased significantly with CMV. Combined MP plus CMV did not decrease P(o) further. With AMV, P(o) was similar to SB and controls. Combined MP plus AMV or MP plus SB decreased P(o) substantially. Combined MP plus CMV, MP plus AMV, or MP plus SB induced myofibrillar disruption that correlated with the reduced P(o). αII-spectrin increased, IGF-1 decreased, and MAF-box mRNA increased in both the CMV group and MP plus CMV group. Short-term, high-dose MP had no additive effects on CMV-induced diaphragm dysfunction. Combined MP plus AMV impaired diaphragm function, but AMV alone did not. We found that acute, high-dose MP produces diaphragm dysfunction depending on the mode of mechanical ventilation.

Inhibitory effect of biopolymer materials on scar formation following trabeculectomy.

AIM: To investigate the inhibitory effects of amniotic membrane, polylactic acid membrane and chitosan membrane on scar formation following trabeculectomy. METHODS: A total of 24 New Zealand white rabbits (48 eyes) were randomly divided into 4 groups: amniotic membrane group, polylactic acid membrane group, chitosan membrane group, and control group, with 6 rabbits (12 eyes) in each group. The left eyes underwent routine trabeculectomy, and the right eyes were considered as controls. Amniotic membrane, polylactic acid membrane and chitosan membrane were respectively installed under sclera flap in three groups, but any treatment was not applied in control group. Intraocular pressure, conjunctival filtering bleb, and anterior chamber inflammation responses were monitored at day 1, 3, 7, 14, 28 and 56 post-operatively. Eyeball tissue underwent histopathological examination at day 56 post-operatively. RESULTS: Fibrocytes and inflammatory cells were reduced in amniotic membrane, polylactic acid membrane and chitosan membrane groups compared to that in control group. At day 1 post-operatively, intraocular pressure was decreased in three membrane groups compared to that in control group. At day 14 post-operatively, the intraocular pressure was decreased significantly, while it of three membrane groups was significantly lower than that of preoperative (P<0.01). There were no significant differences among three membrane groups (P>0.05). Filtering bleb of four groups was clearly observed at day 7 post-operatively, but there was no significant difference in pair-wise comparison. At day 28 and 56 post-operatively, filtering bleb in control group was significantly narrowed compared to that in three membrane groups (P<0.05), but there was no significant difference in pair-wise comparison of three membrane groups. CONCLUSION: All amniotic membrane, polylactic acid membrane and chitosan membrane can effectively inhibit scar formation following trabeculectomy, the effect of amniotic membrane is the best.

Bench study on active exhalation valve performance.

BACKGROUND: Ventilator exhalation-valve performance during the expiratory phase has been studied in depth. An active exhalation valve uses servo-control technology that allows gas to be released from the exhalation valve during the inspiratory phase if the patient makes an expiratory effort. We conducted a bench study of active exhalation valve response to expiratory effort during the inspiratory phase. METHODS: We studied 4 ventilators that have active exhalation valves (Maquet Servo-i, Newport e500, Puritan Bennett 840, and Evita XL) and one that does not (Puritan Bennett 7200ae). With an active test lung we simulated various magnitudes of expiratory effort during the middle of the inspiratory phase. We measured the exhalation resistance and pressure over-shoot during the expiratory effort, and we measured the pressure under-shoot after the expiratory effort. The exhalation resistance of the 7200ae could not be determined because this ventilator did not allow any gas-release through the exhalation valve during the expiratory effort. RESULTS: The exhalation resistance of the Evita XL (6.6 +/- 1.8 cm H(2)O/L/s) was higher than that of the Servo-i (3.0 +/- 1.3 cm H(2)O/L/s), e500 (2.6 +/- 0.8 cm H(2)O/L/s), and 840 (3.5 +/- 0.8 cm H(2)O/L/s) (all P < .001). The magnitude of pressure over-shoot during the expiratory efforts was not significantly different among the 4 ventilators with active exhalation valves. Pressure over-shoot was significantly higher with the 7200ae than with any of other ventilators (all P < .001). CONCLUSIONS: There was a significant difference in exhalation resistance between the Evita XL and the other 3 ventilators with active exhalation valves. All 4 ventilators with active exhalation valves had lower exhalation resistance than the 7200ae.

[The effect of endotoxins on the diaphragmatic contractile function and mitochondrial ultrastructure].

OBJECTIVE: To investigate the diaphragmatic contractile function and mitochondrial ultrastructure in rats with acute lung injury. METHODS: Twenty-eight Sprague-Dawley (SD) rats were allocated randomly into three groups: a control group (n = 10), a lipopolysaccharide (LPS, endotoxins) 4 h group (n =9) and aLPS 24 h group (n =9). Diaphragmatic samples were taken at 4 h and 24 h after 100 microg/kg LPS was instilled into the trachea of the rats. Normal saline (0.5 ml/kg) was instilled in the control group. Then the contractile function of the diaphragmatic samples, including the peak twitch tension, frequency depended force and fatigue index (FI), was tested in vitro. The diaphragmatic ultrastructure was also measured by electron microscopy. SPSS version 15.0 was used for statistical analysis. Data were presented as x +/- s, and means were compared with analysis of variance. RESULTS: The diaphragmatic force-generating capacity and peak twitch tension in LPS4 h group [(3.4 +/- 1.9); (0.9 +/- 0.4) N/cm2 ] decreased significantly compared to the control group [(6.7 +/- 4.3); (2.2 +/- 1.7) N/cm2, F = 3.59 and 3.78 respectively, P <0.05], but a marked recovery was observed in LPS 24 h group [(4.1 +/- 1.2) and (1.2 +/- 0.7) N/cm), P <0.05]. The FI was also reduced remarkably in LPS 4 h and LPS 24 h adL group (0.07 +/- 0.06; 0.12 +/- 0.07) compared to the control group (0.26 +/- 0.14, F = 9.27, P < 0.01. Ultrastructural examination showed mitochondria derangement at LPS 4 h and LPS 24 h groups, including swollen mitochondria with abnormal cristae, and disrupted external membrane of mitochondria. CONCLUSION: Diaphragmatic contractile force-generating capacity decreased remarkably in rats treated with 100 microg/kg LPS, and the diaphragm was susceptible to developing fatigue. These changes may result in respiratory failure.