Sains Malaysiana 54(1)(2025): 265-278

http://doi.org/10.17576/jsm-2025-5401-21

Modulation of a7nAchR for Cardioprotection against Isoprenaline-Induced Myocardial Injury

(Modulasi a7nAchR untuk Kardioperlindung terhadap Kecederaan Miokardium Aruhan Isoprenalin)

CHEE HOOI CHUNG^1,3, MOHAMMAD YUSUF HASAN³, SATIRAH ZAINALABIDIN², CHUA ENG WEE³, AZIZAH UGUSMAN⁴, ZAKIAH JUBRI⁵ & MOHD KAISAN MAHADI^3,*

¹Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 119228
²Centre of Toxicology and Health Risk Study (CORE), Faculty of Health Sciences, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Federal Territory, Malaysia
³Centre for Drug and Herbal Development, Faculty of Pharmacy, Universiti Kebangsaan Malaysia, 50300 Kuala Lumpur, Federal Territory, Malaysia
⁴Department of Physiology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Malaysia
⁵Department of Biochemistry, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Malaysia

Diserahkan: 24 Januari 2024/Diterima: 11 November 2024

Abstract

The α7nAchR gene is expressed in immune cells, including macrophages, and is linked to cardiovascular diseases. The cardioprotective effects of α7nAchR activation against inflammation in isoprenaline-induced myocardial injury are unclear. This study aims to assess the cardioprotective effects of α7nAChR activation on isoprenaline-induced myocardial injury rats. We hypothesized that α7nAChR activation provides cardioprotection against the myocardial injury via the cholinergic anti-inflammatory pathway. Isoprenaline hydrochloride (85 mg/kg) was injected subcutaneously in rats to induce myocardial injury and activated the a7nAchR through daily transcutaneous tragus stimulation for 14 days at 20 Hz, 0.2 ms, and 2 mA. Examination on Langendorff isolated heart perfusion technique showed improvement in cardiac functions. The electrical stimulation affected collagen deposition, circulating troponin T, and circulating inflammatory marker TNFα. The effects were abolished with pharmacological inhibition of α7nAChR. Further, the role of α7nAChR in ischemia-induced inflammation was studied in RAW264.7 macrophages. Inflammation was activated in RAW264.7 macrophages that were treated with glucose-free media, flushed with 95% N₂, and 5% CO₂ for 1 h, and reoxygenated in a normoxic incubator for 24 h. a7nAchR stimulation in the activated macrophages reduced pro-inflammatory markers (NO, TNFα) but did not affect anti-inflammatory (IL10, TGFb) expression levels. The reduction in pro-inflammatory factors was linked to the modulation of the transcriptional regulator NFκB, but not STAT3. Our findings suggest that activation of the cholinergic anti-inflammatory pathway may protect against isoprenaline-induced cardiac injury by improving cardiac performance and regulating inflammatory macrophage activity potentially via the NFκB/TNFα pathway.

Keywords: Inflammation; isoprenaline; myocardial injury; transcutaneous tragus stimulation; α7nAchR

Abstrak

Gen α7nAchR diekspresikan dalam sel imun, termasuk makrofaj dan dikaitkan dengan penyakit kardiovaskular. Kesan kardiopelindung pengaktifan α7nAchR terhadap kecederaan miokardium aruhan isoprenalin adalah tidak diketahui. Kajian ini bertujuan untuk menilai kesan kardiopelindung pengaktifan α7nAChR pada tikus yang mengalami kecederaan miokardium aruhan isoprenalina. Kami membuat hipotesis bahawa pengaktifan α7nAChR menyediakan perlindungan terhadap kecederaan miokardium yang disebabkan oleh isoprenalin melalui laluan anti-radang kolinergik. Isoprenalin hidroklorida (85 mg/kg) telah disuntik secara subkutaneus pada tikus untuk menginduksi kecederaan miokardium dan mengaktifkan α7nAchR melalui rangsangan tragus transkutaneus harian selama 14 hari pada 20 Hz, 0.2 ms dan 2 mA. Pemeriksaan menggunakan teknik perfusi jantung terasing Langendorff menunjukkan peningkatan dalam fungsi jantung. Rangsangan elektrik mempengaruhi pemendapan kolagen, troponin T dalam peredaran dan penanda keradangan TNFα dalam sistem peredaran. Kesan tersebut dihapuskan dengan perencatan farmakologi α7nAChR. Selain itu, peranan α7nAChR dalam keradangan aruhan iskemia dikaji pada makrofaj RAW264.7. Makrofaj RAW264.7 telah mengalami pengaktifan melalui rawatan di dalam medium bebas glukosa, pengaliran dengan 95% N₂, 5% CO₂ selama 1 jam dan dioksigenkan semula dalam inkubator selama 24 jam. Rangsangan α7nAChR dalam makrofaj yang telah diaktifkan mengurangkan penanda pro-radang (NO, TNFα) tetapi tidak mempengaeruhili tahap pengekspresan anti-radang (IL10, TGFβ). Pengurangan faktor pro-radang dikaitkan dengan modulasi pengawal selia transkripsi NFκB, tetapi bukan STAT3. Penemuan kami mencadangkan bahawa pengaktifan laluan anti-radang kolinergik mungkin melindungi daripada kecederaan jantung aruhan isoprenalina dengan meningkatkan prestasi jantung dan mengawal aktiviti makrofaj keradangan, berpotensi melalui laluan tapak NFκB/TNFα.

Kata kunci: Isoprenalin; kecederaan miokardium; keradangan; rangsangan tragus transkutaneus; α7nAchR

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*Pengarang untuk surat-menyurat; email: kaisanmahadi@ukm.edu.my