Keywords
Cardiomyopathy
Ac-SDKP
Claudin-1
Endothelial dysfunction
Vascular permeability
How to Cite
Abstract
Background: Radiation‑induced cardiomyopathy is a significant late complication in cancer survivors treated with thoracic radiation, with few preventive options. Early injury is characterized by coronary microvascular endothelial dysfunction and increased vascular permeability. Claudin‑1 (Cldn1), a tight junction protein in endothelial cells, plays a key role in maintaining vascular barrier integrity. This study investigated whether the endogenous tetrapeptide N‑acetyl‑Ser‑Asp‑Lys‑Pro (Ac‑SDKP) preserves cardiac microvascular barrier function and mitigates early radiation‑associated cardiac injury in preclinical models.
Methods: Human coronary microvascular endothelial cells (HMVECs) were exposed to ionizing radiation (IR) with preventive Ac‑SDKP treatment. Endothelial barrier function was assessed using FITC‑dextran permeability and transendothelial electrical resistance (TEER). In vivo, mice received fractionated left thoracic irradiation (3 Gy/day, 5 days/week; total 45 Gy). Ac‑SDKP (3.2 mg/kg/day) was administered via subcutaneous osmotic minipump starting one day prior to irradiation and continued throughout the study. Cardiac vascular leakage was measured by Evans blue extravasation at early and chronic time points, and left ventricular (LV) function was evaluated by cardiac MRI.
Results: IR decreased Cldn1 expression, increased endothelial permeability, and reduced TEER in HMVECs. Preventive Ac‑SDKP preserved Cldn1 expression and significantly reduced IR‑induced permeability, although TEER recovery was partial. In mice, irradiation reduced cardiac Cldn1 levels, increased vascular leakage, and impaired LV function. Ac‑SDKP reduced early leakage and improved selected functional measures, with no significant effect on chronic permeability.
Conclusion: Preventive Ac‑SDKP attenuates radiation‑related cardiac microvascular dysfunction and partially preserves cardiac function, likely through maintenance of endothelial barrier integrity and Cldn1 expression suggesting potential vascular protective pathways.
References
1. Miller KD, Siegel RL, Lin CC, Mariotto AB, Kramer JL, Rowland JH, Stein KD, Alteri R, Jemal A. Cancer treatment and survivorship statistics, 2016. CA Cancer J Clin. 2016: 271 [PMID: 27253694, https://doi.org/10.3322/caac.21349]
2. Aronow H, Kim M, Rubenfire M. Silent ischemic cardiomyopathy and left coronary ostial stenosis secondary to radiation therapy. Clin Cardiol. 1996: 260 [PMID: 8674269, https://doi.org/10.1002/clc.4960190325]
3. Abe JI, Allen BG, Beyer AM, Lewandowski D, Mapuskar KA, Subramanian V, Tamplin MR, Grumbach IM. Radiation-Induced Macrovessel/Microvessel Disease. Arterioscler Thromb Vasc Biol. 2024: 2407 [PMID: 39445428, https://doi.org/10.1161/ATVBAHA.124.319866]
4. Komarova YA, Kruse K, Mehta D, Malik AB. Protein Interactions at Endothelial Junctions and Signaling Mechanisms Regulating Endothelial Permeability. Circ Res. 2017: 179 [PMID: 28057793, https://doi.org/10.1161/CIRCRESAHA.116.306534]
5. Lee WL, Slutsky AS. Sepsis and endothelial permeability. N Engl J Med. 2010: 689 [PMID: 20818861, https://doi.org/10.1056/NEJMcibr1007320]
6. Furuse M, Hata M, Furuse K, Yoshida Y, Haratake A, Sugitani Y, Noda T, Kubo A, Tsukita S. Claudin-based tight junctions are crucial for the mammalian epidermal barrier: a lesson from claudin-1-deficient mice. J Cell Biol. 2002: 1099 [PMID: 11889141, https://doi.org/10.1083/jcb.200110122]
7. Xia Y, Cao H, Zheng J, Chen L. Claudin-1 Mediated Tight Junction Dysfunction as a Contributor to Atopic March. Front Immunol. 2022: 927465 [PMID: 35844593, https://doi.org/10.3389/fimmu.2022.927465]
8. Nepali S, Chen M, Karthikeyan B, Sonkawade SD, Mahajan SD, Spernyak J, Sharma UC, Pokharel S. Claudin 1 dysregulation disrupts coronary microvascular integrity and impairs cardiac function. Atherosclerosis. 2025: 119149 [PMID: 40068507, https://doi.org/10.1016/j.atherosclerosis.2025.119149]
9. Vasques-Novoa F, Angelico-Goncalves A, Alvarenga JMG, Nobrega J, Cerqueira RJ, Mancio J, Leite-Moreira AF, Roncon-Albuquerque R, Jr. Myocardial oedema: pathophysiological basis and implications for the failing heart. ESC Heart Fail. 2022: 958 [PMID: 35150087, https://doi.org/10.1002/ehf2.13775]
10. Cavasin MA, Rhaleb NE, Yang XP, Carretero OA. Prolyl oligopeptidase is involved in release of the antifibrotic peptide Ac-SDKP. Hypertension. 2004: 1140 [PMID: 15037553, https://doi.org/10.1161/01.HYP.0000126172.01673.84]
11. Lenfant M, Wdzieczak-Bakala J, Guittet E, Prome JC, Sotty D, Frindel E. Inhibitor of hematopoietic pluripotent stem cell proliferation: purification and determination of its structure. Proc Natl Acad Sci U S A. 1989: 779 [PMID: 2915977, https://doi.org/10.1073/pnas.86.3.779]
12. Azizi M, Ezan E, Nicolet L, Grognet JM, Menard J. High plasma level of N-acetyl-seryl-aspartyl-lysyl-proline: a new marker of chronic angiotensin-converting enzyme inhibition. Hypertension. 1997: 1015 [PMID: 9369248, https://doi.org/10.1161/01.hyp.30.5.1015]
13. Sonkawade SD, Xu S, Kim M, Nepali S, Karambizi VG, Sexton S, Turowski SG, Li K, Spernyak JA, Lovell JF, George A, Suwal S, Sharma UC, Pokharel S. Phospholipid Encapsulation of an Anti-Fibrotic Endopeptide to Enhance Cellular Uptake and Myocardial Retention. Cells. 2023: [PMID: 37371059, https://doi.org/10.3390/cells12121589]
14. Pokharel S, van Geel PP, Sharma UC, Cleutjens JP, Bohnemeier H, Tian XL, Schunkert H, Crijns HJ, Paul M, Pinto YM. Increased myocardial collagen content in transgenic rats overexpressing cardiac angiotensin-converting enzyme is related to enhanced breakdown of N-acetyl-Ser-Asp-Lys-Pro and increased phosphorylation of Smad2/3. Circulation. 2004: 3129 [PMID: 15520311, https://doi.org/10.1161/01.CIR.0000147180.87553.79]
15. Peng H, Carretero OA, Vuljaj N, Liao TD, Motivala A, Peterson EL, Rhaleb NE. Angiotensin-converting enzyme inhibitors: a new mechanism of action. Circulation. 2005: 2436 [PMID: 16216963, https://doi.org/10.1161/CIRCULATIONAHA.104.528695]
16. Sharma UC, Sonkawade SD, Baird A, Chen M, Xu S, Sexton S, Singh AK, Groman A, Turowski SG, Spernyak JA, Mahajan SD, Pokharel S. Effects of a novel peptide Ac-SDKP in radiation-induced coronary endothelial damage and resting myocardial blood flow. Cardiooncology. 2018: [PMID: 31057947, https://doi.org/10.1186/s40959-018-0034-1]
17. Sharma UC, Sonkawade SD, Spernyak JA, Sexton S, Nguyen J, Dahal S, Attwood KM, Singh AK, van Berlo JH, Pokharel S. A Small Peptide Ac-SDKP Inhibits Radiation-Induced Cardiomyopathy. Circ Heart Fail. 2018: e004867 [PMID: 30354563, https://doi.org/10.1161/CIRCHEARTFAILURE.117.004867]
18. Karthikeyan B, Sonkawade SD, Pokharel S, Preda M, Schweser F, Zivadinov R, Kim M, Sharma UC. Tagged cine magnetic resonance imaging to quantify regional mechanical changes after acute myocardial infarction. Magn Reson Imaging. 2020: 208 [PMID: 31668928, https://doi.org/10.1016/j.mri.2019.09.010]
19. Radu M, Chernoff J. An in vivo assay to test blood vessel permeability. J Vis Exp. 2013: e50062 [PMID: 23524912, https://doi.org/10.3791/50062]
20. Beckman JA, Thakore A, Kalinowski BH, Harris JR, Creager MA. Radiation therapy impairs endothelium-dependent vasodilation in humans. J Am Coll Cardiol. 2001: 761 [PMID: 11693749, https://doi.org/10.1016/s0735-1097(00)01190-6]
21. Suvorava T, Luksha LS, Lobanok LM. The effects of acute and chronic radiation on endothelium- and no-dependent vascular reactivity. Cell Mol Biol (Noisy-le-grand). 2005: 321 [PMID: 16191400,
22. Reinhold HS, Buisman GH. Radiosensitivity of capillary endothelium. Br J Radiol. 1973: 54 [PMID: 4683331, https://doi.org/10.1259/0007-1285-46-541-54]
23. Gunzel D, Fromm M. Claudins and other tight junction proteins. Compr Physiol. 2012: 1819 [PMID: 23723025, https://doi.org/10.1002/cphy.c110045]
24. Shukla PK, Gangwar R, Manda B, Meena AS, Yadav N, Szabo E, Balogh A, Lee SC, Tigyi G, Rao R. Rapid disruption of intestinal epithelial tight junction and barrier dysfunction by ionizing radiation in mouse colon in vivo: protection by N-acetyl-l-cysteine. Am J Physiol Gastrointest Liver Physiol. 2016: G705 [PMID: 26822914, https://doi.org/10.1152/ajpgi.00314.2015]
25. Khan MY, Ohanian M. Radiation-Induced Cardiomyopathy: II. An Electron Microscopic Study of Myocardial Microvasculature. Am J Pathol. 1974: 125 [PMID: 19971051,
26. RM B, EF Y, , R S, , D I, , WB R, , RM D. Effects of radiation on endothelial barrier and vascular integrity. Tissue Barriers in Disease, Injury and Regeneration 2021: 43
27. Bari WA, Sorenson GD. Ultrastructural Alterations in X-Irradiated Spleen. Pathol Microbiol (Basel). 1964: 257 [PMID: 14132879, https://doi.org/10.1159/000161473]
28. Peng H, Xu J, Yang XP, Kassem KM, Rhaleb IA, Peterson E, Rhaleb NE. N-acetyl-seryl-aspartyl-lysyl-proline treatment protects heart against excessive myocardial injury and heart failure in mice. Can J Physiol Pharmacol. 2019: 753 [PMID: 30998852, https://doi.org/10.1139/cjpp-2019-0047]
29. Sharma U, Rhaleb NE, Pokharel S, Harding P, Rasoul S, Peng H, Carretero OA. Novel anti-inflammatory mechanisms of N-Acetyl-Ser-Asp-Lys-Pro in hypertension-induced target organ damage. Am J Physiol Heart Circ Physiol. 2008: H1226 [PMID: 18178715, https://doi.org/10.1152/ajpheart.00305.2007]
30. Pokharel S, Rasoul S, Roks AJ, van Leeuwen RE, van Luyn MJ, Deelman LE, Smits JF, Carretero O, van Gilst WH, Pinto YM. N-acetyl-Ser-Asp-Lys-Pro inhibits phosphorylation of Smad2 in cardiac fibroblasts. Hypertension. 2002: 155 [PMID: 12154106, https://doi.org/10.1161/01.hyp.0000025880.56816.fa]
31. Dreyfuss AD, Goia D, Shoniyozov K, Shewale SV, Velalopoulou A, Mazzoni S, Avgousti H, Metzler SD, Bravo PE, Feigenberg SJ, Ky B, Verginadis, II, Koumenis C. A Novel Mouse Model of Radiation-Induced Cardiac Injury Reveals Biological and Radiological Biomarkers of Cardiac Dysfunction with Potential Clinical Relevance. Clin Cancer Res. 2021: 2266 [PMID: 33542079, https://doi.org/10.1158/1078-0432.CCR-20-3882]
32. Tokatli F, Uzal C, Doganay L, Kocak Z, Kaya M, Ture M, Kurum T, Alkaya F, Karadag H, Kutlu K. The potential cardioprotective effects of amifostine in irradiated rats. Int J Radiat Oncol Biol Phys. 2004: 1228 [PMID: 15001267, https://doi.org/10.1016/j.ijrobp.2003.09.071]
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Copyright (c) 2026 Sarmila Nepali, Badri Karthikeyan, Swati D Sonkawade, Supriya D Mahajan, Joseph Spernyak, Umesh C Sharma, Saraswati Pokharel