The expression patterns of surfactant protein A (SP‐A) in lung and skeletal muscle in SD rat and plateau zokor (Eospalax baileyi) under the hypoxia environments

doi:10.16829/j.slxb.150940

Abstract

Abstract:

Pulmonary surfactant protein A (Surfactant protein A, SP-A) is the most abundant pulmonary surfactant protein, encoded and synthesized by the SFTPA gene. SP-A is primarily synthesized in the lung tissue of mammals and is also expressed in tissues such as skeletal muscle. SP-A has functions including reducing pulmonary surface tension, enhancing pulmonary gas exchange, regulating immunity, clearing pathogens, and reducing inflammatory responses. In this study, after performing transcriptome sequencing analysis on the liver, lung, skeletal muscle, small intestine, colon, and adipose tissues from SD rats (2 250 m and 3 700 m) and plateau zokors (2 700 m and 3 700 m) at different altitudes; the expression levels of SFTPA gene in skeletal muscle and lung tissues of the two species were compared and analyzed by qRT-PCR; the expression levels of SP-A in skeletal muscle, lung tissue and serum of the two species were compared and analyzed by Western Blotting. The transcriptome analysis revealed that with increasing altitude, the expression of the SFTPA gene in the skeletal muscle of SD rats were significantly up-regulated, while in the skeletal muscle of plateau zokors, there were no significant difference in its expression; the qRT-PCR results showed that with increasing altitude and decreasing environmental oxygen levels, the expression of SFTPA in the skeletal muscle of SD rats increased, whereas in the skeletal muscle of plateau zokors, the expression of SFTPA significantly decreased. Furthermore, the expression of SFTPA in the lung tissues of both SD rats and plateau zokors were significantly decreased; the Western Blotting results showed that with increasing altitude and decreasing environmental oxygen levels, the expression levels of SP-A in the skeletal muscle, serum, and lung tissues of both SD rats and plateau zokors were significantly increased. In conclusion, in a high-altitude hypoxia environment, the transcriptional expression of the SFTPA gene in the lung tissues of SD rats and plateau zokors were significantly decreased. However, the content of SP-A in their lung tissues not only did not decrease but significantly increased. This may be due to SP-A synthesized and secreted by skeletal muscle being transported to the lung tissues via the bloodstream, representing an important mechanism for SD rats and plateau zokors to adapt to hypoxia environments.

Key words: Pulmonary surfactant (PS), Surfactant protein A (SP‐A), High-altitude hypoxia, SD rat, Plateau zokor (Eospalax baileyi)

摘要：

肺表面活性蛋白A (Surfactant protein A, SP‐A) 是最丰富的肺表面活性蛋白，由SFTPA基因编码合成，主要在哺乳动物的肺组织中合成，也在骨骼肌等组织中表达。SP‐A具有降低肺表面张力、增强肺气体交换、调节免疫、清除病原体和降低炎症反应的功能。本研究通过对不同海拔SD大鼠 (2 250 m和3 700 m) 和高原鼢鼠 (Eospalax baileyi) (2 700 m和3 700 m) 肝、肺、骨骼肌、小肠、结肠和脂肪组织转录组测序分析后；利用qRT‑PCR法比较分析SFTPA基因在两个物种骨骼肌和肺组织中的表达水平；利用Western Blotting法比较分析SP‐A在两个物种骨骼肌、肺组织和血清中的表达水平。转录组分析发现，随着海拔升高，大鼠骨骼肌中SFTPA基因表达显著上调，但在高原鼢鼠骨骼肌中其表达没有显著差异；qRT‑PCR结果显示，随着海拔升高，生境氧含量下降，SD大鼠骨骼肌组织中SFTPA表达升高，高原鼢鼠骨骼肌组织中SFTPA表达显著降低，且SD大鼠和高原鼢鼠肺组织中SFTPA表达均显著降低；Western Blotting结果显示，随着海拔升高，生境氧含量下降，在SD大鼠和高原鼢鼠骨骼肌、血清和肺组织中SP‐A的表达水平均显著升高。总之，高海拔低氧环境下，SD大鼠和高原鼢鼠肺组织中SFTPA基因转录表达显著降低，但两个物种肺组织中SP‐A含量不仅没有下降，反而显著升高，这可能是由骨骼肌合成并分泌的SP‐A经血液转运至肺组织的结果，也是SD大鼠习服低氧环境，高原鼢鼠适应低氧环境的重要机制。

关键词: 肺表面活性物质, 肺表面活性蛋白A, 高原低氧, SD大鼠, 高原鼢鼠

CLC Number:

Q494

Xiaoyan PU, Chongyang DAI, Yaxuan WANG, Dengbang WEI. The expression patterns of surfactant protein A (SP‐A) in lung and skeletal muscle in SD rat and plateau zokor (Eospalax baileyi) under the hypoxia environments[J]. ACTA THERIOLOGICA SINICA, 2025, 45(3): 283-294.

蒲小燕, 戴重阳, 王雅轩, 魏登邦. 低氧环境下高原鼢鼠及SD大鼠肺和骨骼肌中SP‑A的表达模式[J]. 兽类学报, 2025, 45(3): 283-294.

Figures/Tables 7

Table 1 Sequencing data statistics and sequence alignment analysis of muscle tissues transcripts from SD rat and plateau zokor

样本 Sample	原始读数 Raw reads	清洁读数 Clean reads	错误率 Error rate/%	碱基质量值 Q20/%	碱基质量值 Q30/%
RL_JR_1	60792716	60326478	0.025 1	98.10	94.15
RL_JR_2	58037480	56085200	0.025 3	97.96	93.89
RL_JR_3	63848522	61660090	0.025 9	97.75	93.39
RH_JR_1	50958280	49219200	0.025 8	97.80	93.45
RH_JR_2	55253402	52263220	0.026 2	97.61	93.06
RH_JR_3	47158104	44837466	0.026 1	97.65	93.10
ZL_JR_1	44498698	43993632	0.026 1	97.49	93.17
ZLJ_JR_2	46066694	45538394	0.023 3	97.59	93.36
ZLJ_JR_3	48235896	47710310	0.026 5	97.33	92.79
ZHJ_JR_1	41859668	41039026	0.027 0	97.13	92.43
ZHJ_JR_2	45660114	45068504	0.026 6	97.29	92.74
ZHJ_JR_3	45736038	45095202	0.026 4	97.39	92.95

Fig. 1 Transcriptome analysis of skeletal muscle in SD rat at different altitudes. A: PCA analysis of transcripts; B: Differential gene volcano map; C: GO enrichment analysis; D: KEGG pathway enrichment analysis of up-regulated differential genes; E: KEGG pathway enrichment analysis of down-regulated differential genes; F: TPM values of SFTPA gene in each sample; G: SFTPA gene expression differences between the two groups. RL and RH refers to SD rats in the low-altitude group and SD rats in the high-altitude group (n = 3)

Table 2 Differential expression of genes in skeletal muscle tissue of SD rats at different altitudes

基因名称 Gene name	表达差异倍数 Log2FC	P 值 P value	显著性 Significant	趋势 Regulate
Sftpc	7.375 081 543	0.015 5	Yes	上调Up
Rab1b	7.138 197 744	0.021 2	Yes	上调Up
SFTPA	6.863 194 973	0.008 0	Yes	上调Up
Pitx1	6.419 578 930	< 0.001	Yes	上调Up
Nectin4	6.174 529 850	0.024 7	Yes	上调Up
Pnma1	-6.151 937 528	0.016 0	Yes	下调Down
Taf13	6.036 091 339	0.022 6	Yes	上调Up
Chia	6.025 407 012	0.042 7	Yes	上调Up
Fetub	5.789 343 533	0.044 0	Yes	上调Up
Ttr	5.716 509 656	0.041 8	Yes	上调Up

Fig. 2 Transcriptome analysis of skeletal muscle in plateau zokor at different altitudes. A: PCA analysis of transcripts; B: Differential gene volcano map; C: GO enrichment analysis; D: KEGG pathway enrichment analysis of up-regulated differential genes; E: KEGG pathway enrichment analysis of down-regulated differential genes. ZL and ZH refers to plateau zokor in the low-altitude group and plateau zokor in the high-altitude group (n = 3)

Fig. 3 The expression levels of SFTPA and SP-A protein in skeletal muscle of SD rat and plateau zokor. * P < 0.05, *** P < 0.001

Fig. 4 The expression levels of SP‐A protein in serum of SD rat and plateau zokor. * P < 0.05

Fig. 5 The expression levels of SFTPA and SP-A protein in lung of SD rat and plateau zokor. * P < 0.05, ** P < 0.01

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