Histidine dipeptides are key regulators of excitation-contraction coupling in cardiac muscle: Evidence from a novel CARNS1 knockout rat model

• Main Authors: Lívia de Souza Gonçalves, Lucas Peixoto Sales, Tiemi Raquel Saito, Juliane Cruz Campos, Alan Lins Fernandes, José Natali, Leonardo Jensen, Alexandre Arnold, Lisley Ramalho, Luiz Roberto Grassmann Bechara, Marcos Vinicius Esteca, Isis Correa, Diogo Sant'Anna, Alexandre Ceroni, Lisete Compagno Michelini, Bruno Gualano, Walcy Teodoro, Victor Henrique Carvalho, Bianca Scigliano Vargas, Marisa Helena Gennari Medeiros, Igor Luchini Baptista, Maria Cláudia Irigoyen, Craig Sale, Julio Cesar Batista Ferreira, Guilherme Giannini Artioli
• Format: Article
• Language: English
• Published: Elsevier 2021-08-01
• Series: Redox Biology
• Subjects: Carnosine; Cardiac dysfunction; Carnosine synthase; Skeletal muscle; Cardiac muscle; Calcium transient
• Online Access: http://www.sciencedirect.com/science/article/pii/S2213231721001749

Histidine-containing dipeptides (HCDs) are abundantly expressed in striated muscles. Although important properties have been ascribed to HCDs, including H+ buffering, regulation of Ca2+ transients and protection against oxidative stress, it remains unknown whether they play relevant functions in vivo. To investigate the in vivo roles of HCDs, we developed the first carnosine synthase knockout (CARNS1−/−) rat strain to investigate the impact of an absence of HCDs on skeletal and cardiac muscle function. Male wild-type (WT) and knockout rats (4 months-old) were used. Skeletal muscle function was assessed by an exercise tolerance test, contractile function in situ and muscle buffering capacity in vitro. Cardiac function was assessed in vivo by echocardiography and cardiac electrical activity by electrocardiography. Cardiomyocyte contractile function was assessed in isolated cardiomyocytes by measuring sarcomere contractility, along with the determination of Ca2+ transient. Markers of oxidative stress, mitochondrial function and expression of proteins were also evaluated in cardiac muscle. Animals were supplemented with carnosine (1.8% in drinking water for 12 weeks) in an attempt to rescue tissue HCDs levels and function. CARNS1−/− resulted in the complete absence of carnosine and anserine, but it did not affect exercise capacity, skeletal muscle force production, fatigability or buffering capacity in vitro, indicating that these are not essential for pH regulation and function in skeletal muscle. In cardiac muscle, however, CARNS1−/− resulted in a significant impairment of contractile function, which was confirmed both in vivo and ex vivo in isolated sarcomeres. Impaired systolic and diastolic dysfunction were accompanied by reduced intracellular Ca2+ peaks and slowed Ca2+ removal, but not by increased markers of oxidative stress or impaired mitochondrial respiration. No relevant increases in muscle carnosine content were observed after carnosine supplementation. Results show that a primary function of HCDs in cardiac muscle is the regulation of Ca2+ handling and excitation-contraction coupling.