Kosin Med J.  2023 Sep;38(3):184-192. 10.7180/kmj.23.112.

Omega-3 fatty acids upregulate Nrf2 expression and attenuate apoptosis, inflammation, and fibrosis in a rat model of cyclosporine-induced nephropathy

• Lee JY
• Son YK
• Lee MH
• Lee SM
• Kim SE
• An WS

• KMID: 2546153
• DOI: http://doi.org/10.7180/kmj.23.112

Abstract

Background
Cyclosporine A (CsA)-induced kidney injury is characterized by renal impairment with inflammatory cell infiltrations, apoptosis, fibrosis, and hypoxic injury. It is not clear whether omega-3 fatty acids (O-3 FAs), which have anti-inflammatory and antioxidant roles, affect nuclear factor erythroid 2-related factor 2 (Nrf2) expression. The aim of this study was to investigate whether O-3 FAs affect Nrf2 expression and exert anti-inflammatory, anti-apoptotic, and anti-fibrotic effects in CsA-induced nephropathy.
Methods
Male Sprague-Dawley rats were divided into control, CsA-treated, and CsA-treated with O-3 FA groups. Nrf2 expression was measured by Western blots and immunohistochemical staining.
Results
Kidney function was impaired in the CsA-treated rats compared to the controls. Caspase-3 and caspase-7 were activated in the CsA-treated group, and the Bax/Bcl2 ratio was higher. O-3 FAs attenuated these apoptosis-related changes. ED-1 and inhibition of kappa B (IĸB) protein expression were significantly upregulated in the CsA-treated group. Compared to the control group, O-3 FA supplementation attenuated the increased expression of ED-1 and IĸB related to inflammation. Smad2/3, Smad4, and transforming growth factor-β1 were activated in the CsA group, and O-3 FA treatment prevented these changes related to renal fibrosis. The expression of Nrf2 was reduced in CsA-treated rats, but Nrf-2 was increased by O-3 FA treatment.
Conclusions
We suggest that Nrf2 is a potential mediator induced by O-3 FA supplementation and that it attenuates pro-inflammatory pathways, fibrotic processes, and apoptosis. Further studies are needed to elucidate the crosstalk between Nrf2 expression and signals related to O-3 FA treatment.

Keyword

Apoptosis; Cyclosporine; Fibrosis; Inflammation; Omega-3 fatty acid; Nrf2

Figure

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  Fig. 1. Morphological changes in the kidneys in the three groups. Periodic acid-Schiff-stained sections were examined using a light microscope (original magnification, ×200). Treatment of rats with cyclosporine for 4 weeks induced interstitial fibrosis, inflammatory cell infiltration, and tubular atrophy (B) compared to the controls (A). Omega-3 fatty acid supplementation decreased the pathologic changes (C).

• 

  Fig. 2. Expression of caspase-3 (A) and caspase-7 (B) in the kidneys of cyclosporine A (CsA)-induced rats detected by Western blots. Compared to the control group, increased expression of caspase-3 and caspase-7 was shown in the kidneys of the CsA group, and omega-3 fatty acid (O-3 FA) supplementation reversed these effects. *p<0.05, compared to control, **p<0.05, compared to the CsA group.

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  Fig. 3. Bax and Bcl-2 expression in the kidneys of cyclosporine A (CsA)-induced rats. Compared to the control group, CsA treatment increased the expression of pro-apoptotic Bax (A) and attenuated the expression of anti-apoptotic Bcl-2 (B). Omega-3 fatty acid (O-3 FA) supplementation attenuated the upregulation of Bax and increased that of the anti-apoptotic protein Bcl-2. *p<0.05 compared to control, **p<0.05 compared to the CsA group.

• 

  Fig. 4. ED-1 and IĸB expression in the kidneys of cyclosporine A (CsA)-induced rats. Compared to the control group, significantly increased expression of ED-1 (A) and IĸB (B) was observed in CsA-treated rats, which was ameliorated by omega-3 fatty acid (O-3 FA) treatment. *p<0.05 compared to control, **p<0.05 compared to the CsA group.

• 

  Fig. 5. Smads2/3, Smad4, and transforming growth factor-β1 (TGF-β) expression in the kidneys of cyclosporine A (CsA)-induced rats. Compared to the control group, CsA treatment significantly increased the expression of TGF-β1, Smad2/3, and Smad4. Omega-3 fatty acid (O-3 FA) supplementation significantly prevented the upregulation of TGF-β1, Smad2/3, and Smad4. *p<0.05 compared to control, **p<0.05 compared to the CsA group.

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  Fig. 6. Nuclear factor erythroid 2-related factor 2 (Nrf2) expression in the kidney of cyclosporine A (CsA)-induced rats detected by Western blots. (A) Compared to the control group, Nrf2 expression was downregulated in the kidneys of the CsA group and upregulated by omega-3 fatty acid (O-3 FA) supplementation. (B) Immunohistochemically stained specimens from the control group. Nrf2 was mainly expressed in the tubules of the normal control rats. (C) Nrf2 expression was increased in the kidneys of CsA-induced rats. (D) Nrf2 expression was decreased by O-3 FA supplementation in the kidney of CsA-induced rats. *p<0.05 compared to control, **p<0.05, compared to the CsA group.

Reference

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