Salt-induced phosphoproteomic changes in the subfornical organ in rats with chronic kidney disease

Abstract

Objectives

Subfornical organ (SFO) is vital in chronic kidney disease (CKD) progression caused by high salt levels. The current study investigated the effects of high salt on phosphoproteomic changes in SFO in CKD rats.

Methods

5/6 nephrectomized rats were fed a normal-salt diet (0.4%) (NC group) or a high-salt diet (4%) (HC group) for three weeks, while sham-operated rats were fed a normal-salt diet (0.4%) (NS group). For phosphoproteomic analysis of SFO in different groups, TiO₂ enrichment, isobaric tags for relative and absolute quantification (iTRAQ) labeling, and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used.

Results

There were 6808 distinct phosphopeptides found, which corresponded to 2661 phosphoproteins. NC group had 168 upregulated and 250 downregulated phosphopeptides compared to NS group. Comparison to NC group, HC group had 154 upregulated and 124 downregulated phosphopeptides. Growth associated protein 43 (GAP43) and heat shock protein 27 (Hsp27) were significantly upregulated phosphoproteins and may protect against high-salt damage. Differential phosphoproteins with tight functional connection were synapse proteins and microtubule-associated proteins, implying that high-salt diet disrupted brain’s structure and function. Furthermore, differential phosphoproteins in HC/NC comparison group were annotated to participate in GABAergic synapse signaling pathway and aldosterone synthesis and secretion, which attenuated inhibitory neurotransmitter effects and increased sympathetic nerve activity (SNA).

Discussion

This large scale phosphoproteomic profiling of SFO sheds light on how salt aggravates CKD via the central nervous system.

Keywords:

• High-salt diet
• chronic kidney disease
• subfornical organ
• phosphopeptides

Author contributions

Aiqing Li conceived the idea and supervised the project. Xin Wang and Huizhen Wang wrote the paper. Xin Wang, Huizhen Wang, Jiawen Li, Lanying Li, and Yifan Wang performed the experiments and analyzed the data. All the authors discussed, commented on, and revised the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by grants from the National Natural Science Foundation of China [Nos. 81770727 and 82270742], GDUPS (2017), Key Project of Guangzhou Science Technology and Innovation Commission [No. 201804020054], and the Natural Science Foundation of Guangdong [No. 2021A1515011376].