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[Influence of various ventilation manier on rat's lung and the expression of lung endotoxin receptor CD14 mRNA]
Ke-Zhong Li1, Shang-Long Yao, Zhi-Gang Wang
1Department of Anesthesiology, the Second Hospital of Shandong University, Jinan 250033, China.
Objective:
To observe the influence of mechanical ventilation (MV) on rat's lung and the expression changes of lung endotoxin receptor CD14 mRNA.
Methods:
Forty-eight male SD rats weighing 330-360 g were randomly divided into 4 groups (n = 12 each): group R received no mechanical ventilation, group P received small MV (VT = 6 ml/kg, PEEP = 8 mm Hg), group M received conventional MV (VT = 12 ml/kg, PEEP = 0 mm Hg), and group N received large tidal volume mechanical ventilation (VT = 40 ml/kg, PEEP = 0 mm Hg). The animals were anesthetized with intraperitoneal pentobarbital 100 mg x kg(-1), tracheotomized and mechanically ventilated (I:E = 1:1, FiO2 = 21%). The respiratory rate (RR) of MV was adjusted to maintain the end-tidal carbon dioxide in the rang of 35-45 mm Hg throughout the procedure. Right carotid artery and left femoral vein were cannulated for BP monitoring and fluid and drug administration. 6 rats in each group were injected 50 mg/kg Evans Blue (EB). The experiment was culminated in 3 hours, then the rats were killed by exsanguination via arteria carotis interna. Morphologic change scores of the rats' lungs, wet/dry weight ratio of lung tissue (W/D), bronchial lavage fluid (BALF) inflammatory cell population, and permeability of vessel wall were evaluated. The concentration of TNF-alpha and MIP-2 in the plasma were determined by enzyme immunoassay method (ELISA). The expressions of lung tissue endotoxin receptor CD14 were detected by RT-PCR, macrophage CD14 in BALF was also detected by immunohistochemistry.
Results:
pulmonary pathomorphology scores: there were no alteration in R group and P group, but it were slightly increased in M group, there was significantly elevated in N group as compare to M group (F = 8.0, P = 0.000). Pulmonary tissue wet/dry weight ratio (W/D): Compare with R group, There was no statistically significant difference in P group and M group; the elevation in N group (t = 4.103, P = 0.02), EB: Compare with R group, There was no statistically significant difference in P group and M group; the obviously elevation in N group (t = 36.634, P = 0.000). WBC in BALF: Compare with R group, there was no change in P group, the elevation in M group (t = 4.272, P = 0.02), there was significantly elevated in N group (F = 26.68, P = 0.000). TNF-alpha had no manifest variation in 4 groups. MIP-2: compare with R group (31.5 +/- 2.4), There was no statistically significant difference in P group (35.4 +/- 5.3), the elevation in M group (44.7 +/- 6.9, t = 7.85, P = 0.04), there was significantly elevated in N group (167.7 +/- 11.8, t = 27.779, P = 0.000). The expressions of macrophage CD14 protein in BALF and lung tissue CD14 mRNA were fundamentally coincident in R group and P group; the expressions of CD14 mRNA were elevated, but the expressions of CD14 protein were no change in M group; the expressions of CD14 in N group manifestly elevated (P = 0.000).
Conclusions:
Conventional MV induces minor injury in rat's lung and can up regulate the expression of CD14 mRNA in the lung, but not up regulate the expression of CD14 protein; large tidal volume MV induces injury of rat's lung and evidently up regulates CD14 expression in the lung. Protective MV can avoid the above mentioned variations in rat's lung.
Insights
Mechanical ventilation (MV) can cause lung injury in rats. Large tidal volume MV significantly increases lung injury and CD14 expression, while protective MV avoids these effects.
Area of Science:
- Pulmonary Medicine
- Critical Care Medicine
- Molecular Biology
Background:
- Mechanical ventilation (MV) is a life-support treatment for respiratory failure.
- Different MV strategies may impact lung injury and inflammatory responses.
- The role of CD14, an endotoxin receptor, in ventilation-induced lung injury (VILI) requires further investigation.
Purpose of the Study:
- To investigate the effects of varying mechanical ventilation (MV) parameters on rat lungs.
- To examine the changes in lung endotoxin receptor CD14 mRNA and protein expression under different MV settings.
Main Methods:
- Male Sprague-Dawley rats were divided into four groups: no MV, small tidal volume (VT), conventional MV, and large VT.
- Lung injury was assessed by pathomorphology scores, wet/dry weight ratio, Evans Blue extravasation, and inflammatory cell counts in bronchoalveolar lavage fluid (BALF).
- Plasma cytokine levels (TNF-alpha, MIP-2) and CD14 expression in lung tissue and BALF were measured using ELISA, RT-PCR, and immunohistochemistry.
Main Results:
- Large tidal volume MV significantly increased lung injury scores, wet/dry weight ratio, vascular permeability, and inflammatory cell counts compared to control and conventional MV groups.
- Conventional MV showed minor increases in lung injury markers and upregulated CD14 mRNA but not protein.
- Large tidal volume MV markedly upregulated both CD14 mRNA and protein expression in lung tissue and BALF.
Conclusions:
- Protective mechanical ventilation (small VT) can prevent lung injury and associated CD14 expression changes.
- Conventional MV may induce minor lung injury and alter CD14 mRNA expression.
- Large tidal volume MV causes significant lung injury and markedly upregulates CD14 expression, suggesting its involvement in VILI.
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