QSOX1 was identified as a new biomarker of acute heart failure (AHF). Using a proteomics strategy on plasma, QSOX1, which exists in 2 isoforms (short S and long L form), emerged as a promising marker to differentiate dyspnea caused by AHF from other syndromes. Preliminary results from our group suggested a protective role of OSOX1 cardiac induction in AHF. We developed an AHF murine model by isoproterenol injections. To further study the role of QSOX1 during AHF, we used antisense oligonucleotides (AOs) and we generated a knock-out (KO) mouse for QSOX1.
AHF was provoked by two daily injections of 150 mg/kg of Isoproterenol (ISO) for two days; control mice (C) received NaCl 0.09‰ injections. Mice were sacrificed the third day, after cardiac function has been assessed by echocardiography. To silence QSOX1 expression, mice were treated by intraperitoneal injection of antisense oligonucleotides (AOs) for QSOX1. QSOX1 cardiac expression was analyzed by RT-qPCR, immunoblotting and immonofluorescence. In parallel, embryonic stem cell clone QSOX1tm1a (KOMP), in which the QSOX1 gene is invalidated, were injected into mouse blastocysts (SEAT platform, France). The KO constructs contain a promoter-less lacZ gene that is under the control of the QSOX1 regulatory sequences. QSOX1+/- heterozygotes mice were obtained from chimeric mice.
The ISO mice exhibited a decrease in shortening fraction (C = 35.0 ± 0.4 %; ISO = 27.2 ± 3.3 %; p<0,001), a left ventricular hypertrophy (C= 4.42 ± 0.2 mg/g; ISO= 5.34 ± 0.3 mg/g; p<0.001) and a pulmonary congestion evaluated with lung weight/body weight ratio (C= 5.24±0.08 mg/g; ISO= 6.10±0.22 mg/g; p<0.001). A cardiac induction of QSOX1 mRNA was observed in AHF mice (x2.1, p<0,01) concomitantly to BNP (x3, p<0,01). AOs treatment enhanced AHF signs in ISO mice (increase in pulmonary congestion p<0.05). QSOX1 gene invalidation is homozygous viable and fertile. Echocardiography measurements showed that adult mice had no cardiac morphological or vascular abnormality. At basal level, lacZ expression was elevated in the epididymis, trachea and arteries, as previously described. In the heart, we observed that after ISO injection, the decrease in shortening fraction as measured by echography was accompanied by an increase in lacZ expression in the cardiomyocytes.
The data suggest that QSOX1 is a new biomarker of ADHF and plays a role in the process. The QSOX1 KO mouse model should help to define QSOX1 function in AHF.