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. 2022 Aug 11;8(8):e10184.
doi: 10.1016/j.heliyon.2022.e10184. eCollection 2022 Aug.

Exposure to airborne particulate matter induces renal tubular cell injury in vitro: the role of vitamin D signaling and renin-angiotensin system

Eungu Kang  1 , Hyung Eun Yim  1 , Yoon Jeong Nam  2 , Sang Hoon Jeong  2 , Joo-Ae Kim  3 , Ju-Han Lee  4 , Min Hwa Son  1 , Kee Hwan Yoo  5
Affiliations

Exposure to airborne particulate matter induces renal tubular cell injury in vitro: the role of vitamin D signaling and renin-angiotensin system

Eungu Kang et al. Heliyon. .

Abstract

Background: Exposure to air pollution can interfere with the vitamin D endocrine system. This study investigated the effects of airborne particulate matter (PM) on renal tubular cell injury in vitro and explored the underlying mechanisms.

Methods: HK-2 human renal proximal tubule cells were treated with PM with or without 1,25(OH)2D3 analog, 19-Nor-1,25(OH)2D2 (paricalcitol, 10 nM) for 48 h. The dose- and time-dependent cytotoxicity of PM with or without paricalcitol was determined via cell counting kit-8 assay. Cellular oxidative stress was assessed using commercially available enzyme-linked immunosorbent assay kits. The protein expression of vitamin D receptor (VDR), cytochrome P450(CYP)27B1, CYP24A1, renin, angiotensin converting enzyme (ACE), angiotensin II type 1 receptor (AT1), nuclear factor erythroid 2-related factor 2 (Nrf2), nuclear factor-kB (NF-kB), tumor necrosis factor (TNF)-α, and interleukin (IL)-6 was determined.

Results: PM exposure decreased HK-2 cell viability in a dose- and time-dependent manner. The activities of superoxide dismutase and malondialdehyde in HK-2 cells increased significantly in the group exposed to PM. PM exposure decreased VDR and Nrf2, while increasing CYP27B1, renin, ACE, AT1, NF-kB, TNF-α, and IL-6. The expression of VDR, CYP27B1, renin, ACE, AT1, and TNF-α was reversed by paricalcitol treatment. Paricalcitol also restored the cell viability of PM-exposed HK-2 cells.

Conclusion: Our findings indicate that exposure to PM induces renal proximal tubular cell injury, concomitant with alteration of vitamin D endocrine system and renin angiotensin system. Vitamin D could attenuate renal tubular cell damage following PM exposure by suppressing the renin-angiotensin system and by partially inhibiting the inflammatory response.

Keywords: Airborne particulate matter; Kidney tubules; Renin-angiotensin system; Vitamin D deficiency.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Effects of PM on the morphology of HK-2 cells. (a, e) NC group. (b, f) NC with vitamin D group. (c, g) PM group. (d, h) PM with vitamin D group. Representative pictures show the loss of physiological cell shape and decrease in cell number after PM exposure (c, g). Vitamin D treatment following PM stimulation restored the cellular morphology and reduced cell number (d, h) (a–d, x5 magnification; e–h, x20 magnification). PM, particulate matter; NC, normal culture media.
Figure 2
Figure 2
Effects of PM with or without vitamin D on the viability of HK-2 cells. (a) Dose-dependent cell viability after stimulation with different concentrations of PBS or PM (∗P < 0.05, PM 25% vs. PM 0%, 1%, 10%, 50%, 75%; ∗∗P < 0.05, PM 50% vs. PM 0%, 1%, 10%, 25%, 75%; ∗∗∗P < 0.05, PM 75% vs. PM 0%, 1%, 10%, 25%, 50%; †P < 0.05, PBS 50% vs. PBS 0%, 10%, 75%; ‡P < 0.05, PBS 75% vs. PBS 0%, 1% 10%, 25%, 50%; #P < 0.05, PBS 50% vs. PM 50%; ##P < 0.05, PBS 75% vs. PM 75%). (b) Time-dependent cell viability after PM75% exposure (∗P < 0.05, 6 h vs. 0, 24, 48 h; ∗∗P < 0.05, 12 h vs. 0, 24, 48 h; †P < 0.05, 24 h vs. 0, 6, 12, 48 h; ‡P < 0.05, 48 h vs. 0, 6, 12, 24 h; #P < 0.05, NC vs. PM75%). (c) Cell viability after treatment with different concentrations of vitamin D following PM stimulation (∗with Vit D 0 nM, P < 0.05, NC vs. PM 60%, PM 75%; ∗∗with PM 50%, 60%, 75%, P < 0.05, Vit D, 0 nM vs. VitD 10 nM, VitD 100 nM). (d) Cell viability after vitamin D (10 nM) treatment following PM75% exposure (∗P < 0.05, PM, PM + Vit D vs. NC, NC + Vit D; ∗∗P < 0.05, PM vs. NC, NC + Vit D, PM + Vit D; †P < 0.05, PM + Vit D vs. NC, NC + Vit D, PM). Values are expressed as the mean ± standard deviation of three (or more) independent experiments. PM, particulate matter; PBS, phosphate-buffered saline; h, hour; NC, normal culture media; VitD, vitamin D.
Figure 3
Figure 3
Effects of PM with or without vitamin D on the protein expression of VDR, CYP27B1, and CYP24A1 in HK-2 cells. (a) VDR (∗P < 0.05, PM vs. NC, NC + Vit D, PM + Vit D; ∗∗P < 0.05, PM + Vit D vs. NC, NC + Vit D, PM). (b) CYP27B1 (∗P < 0.05, PM vs. NC, NC + Vit D, PM + Vit D; ∗∗P < 0.05, PM + Vit D vs. NC, PM). (c) CYP24A1. Values are expressed as the mean ± standard deviation of three (or more) independent experiments. PM, particulate matter; VDR, vitamin D receptor; CYP, cytochrome P450 mixed-function oxidase; NC, normal culture media; VitD, vitamin D.
Figure 4
Figure 4
Effects of PM with or without vitamin D on the levels of renin, ACE, and AT1 in HK-2 cells. (a) renin (∗P < 0.05, PM vs. NC, NC + Vit D, PM + Vit D). (b) ACE (∗P < 0.05, PM vs. NC, NC + Vit D, PM + Vit D). (c) AT1 (∗P < 0.05, PM vs. NC, PM + VitD). Values are expressed as the mean ± standard deviation of three (or more) independent experiments. PM, particulate matter; ACE, angiotensin-converting enzyme; AT1, angiotensin II type 1 receptor; NC, normal culture media; VitD, vitamin D.
Figure 5
Figure 5
Effects of PM with or without vitamin D on the levels of Nrf2, NF-kB p65, TNF-α, and IL-6 in HK-2 cells. (a) Nrf2 (∗P < 0.05, PM vs. NC, NC + Vit D; ∗∗P < 0.05, PM + Vit D vs. NC, NC + Vit D). (b) NF-κB p65 (∗P < 0.05, PM vs. NC). (c) TNF-α (∗P < 0.05, PM vs. NC, NC + Vit D, PM + Vit D). (d) IL-6 (∗P < 0.05, PM vs. NC; ∗∗P < 0.05, PM + Vit D vs. NC). Values are expressed as the mean ± standard deviation of three (or more) independent experiments. PM, particulate matter; Nrf2, nuclear factor erythroid 2-related factor 2; NF-kB p65, nuclear factor kappa B p65; TNF-α, tumor necrosis factor- α; IL-6, interleukin-6; NC, normal culture media; VitD, vitamin D.
Figure 6
Figure 6
Effects of PM with or without vitamin D on the activities of SOD and MDA in HK-2 cells. (a) SOD (∗P < 0.05, PM vs. NC, NC + Vit D; ∗∗P < 0.05, PM + Vit D vs. NC, NC + Vit D). (b) MDA (∗P < 0.05, PM vs. NC, NC + Vit D). Values are expressed as the mean ± standard deviation of three (or more) independent experiments. PM, particulate matter; SOD, superoxide dismutase; MDA, malondialdehyde; NC, normal culture media; VitD, vitamin D.
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