An in vitro endothelial cell protective effect of secretory leukocyte protease inhibitor against simulated ischaemia/reperfusion injury

Vitamin D deficiency induces erectile dysfunction: Role of superoxide and Slpi

BACKGROUND AND PURPOSE

Epidemiological studies suggest a relationship between vitamin D deficiency and erectile dysfunction (ED). We hypothesized that vitamin D deficiency or vitamin D receptor (VDR) knockout causes ED and analysed the underlying molecular mechanisms.

EXPERIMENTAL APPROACH

Erectile function was assessed in vivo in anaesthetized male mice or rats by evaluating intracavernosal pressure (ICP) and in vitro in male Vdr-/- mice, and rat or human isolated corpora cavernosa (CCs) mounted in a myograph. Bulk RNA-sequencing (RNA-seq) transcriptomic analysis was performed in rat CCs. Vitamin D deficiency was induced in rats fed a vitamin D-free diet for 5 months.

KEY RESULTS

CCs from human donors with low plasma vitamin D exhibited reduced nitric oxide (NO)-dependent erectile function. This ED was also reproduced in vitamin D-deficient rats and VDR knockout mice, in vivo and ex vivo, and is associated with penile fibrosis and reduced response to the phosphodiesterase 5 inhibitor (PDE5i) sildenafil. CCs from deficient rats show increased superoxide levels, and their impaired erectile function was restored by superoxide scavengers. Transcriptomic analysis, real-time polymerase chain reaction (RT-PCR) and Western blot showed down-regulated secretory leukocyte protease inhibitor (Slpi). Moreover, recombinant SLPI prevented superoxide-induced ED, while Slpi gene silencing led to reduced erectile function in a superoxide-dependent manner.

CONCLUSION AND IMPLICATIONS

Vitamin D deficiency or VDR knockout reduces erectile function. We suggest that this effect is mediated by increased superoxide levels and down-regulation of SLPI. Vitamin D deficiency might be an aetiological factor for vascular ED and for the therapeutic failure of PDE5i.

Gelatin-coated silicon oxide nanoparticles encapsulated recombinant human secretory leukocyte protease inhibitor (rhSLPI) reduced cardiac cell death against an in vitro simulated ischaemia/reperfusion injury

Ischemic Heart Disease (IHD) is the main global cause of death. Previous studies indicated that recombinant human secretory leukocyte protease inhibitor (rhSLPI) exhibits a cardioprotective effect against myocardial ischaemia/reperfusion (I/R) injury. However, SLPI has a short half-life in vivo due to digestion by protease enzymes in circulation. The application of nanoparticle encapsulation could be beneficial for SLPI delivery. Several types of nanoparticles have been developed to encapsulate SLPI and applied in some disease models. However, silica nanoparticles for rhSLPI delivery, particularly on myocardial I/R injury, have never been studied. In this study, we aimed to fabricate gelatin-covered silica nanoparticles (GSNPs) to encapsulate rhSLPI and cardioprotective effect of GSNP-SLPI against an in vitro simulated ischaemia/reperfusion (sI/R). Silica dioxide nanoparticles (SNPs) were fabricated followed by incubation with 0.33 mg/mL of rhSLPI. Then, SNPs containing rhSLPI were coated with gelatin (GSNPs). The GSNPs and rhSLPI-GSNPs were characterized by particle size, zeta potential, and morphology scanning electron microscope (SEM). The concentration of rhSLPI in rhSLPI-GSNPs and drug release was determined by ELISA. Then, cytotoxicity and cardioprotective effect were determined by incubation of GSNPs or rhSLPI-GSNPs with rat cardiac myoblast cell line (H9c2) subjected to simulated ischaemia/reperfusion (sI/R). The results showed the particle size of SNPs, GSNPs, and rhSLPI-GSNPs was 273, 300, and 301 nm, with a zeta potential of -57.21, -22.40, and -24.50 mV, respectively. One milligram of rhSLPI-GSNPs contains 235 ng of rhSLPI. The rhSLPI-GSNPs showed no cytotoxicity on cardiac cells. Treatment with 10 μg/ml of rhSLPI-GSNPs could significantly reduce sI/R induced cardiac cell injury and death. In conclusion, this is the first study to show successful of fabricating novel rhSLPI-encapsulating gelatin-covered silica nanoparticles (rhSLPI-GSNPs) and the cardioprotective effects of rhSLPI-GSNPs against cardiac cell injury and death from myocardial ischaemia/reperfusion.

Adeno-associated virus 9 vector-mediated cardiac-selective expression of human secretory leukocyte protease inhibitor attenuates myocardial ischemia/reperfusion injury

Protease enzymes contribute to the initiation of cardiac remodeling and heart failure after myocardial ischemic/reperfusion (I/R) injury. Protease inhibitors attenuate protease activity and limit left ventricular dysfunction and remodeling. Previous studies showed the cardioprotective effect of secretory leukocyte protease inhibitor (SLPI) against I/R injury. However, overexpression of SLPI gene in cardiovascular diseases has only been investigated in an in vitro experiment. Here, cardiac-selective expression of the human secretory leukocyte protease inhibitor (hSLPI) gene and its effect on I/R injury were investigated. Adeno-associated virus (AAV) serotype 9 carrying hSLPI under the control of cardiac-selective expression promoter (cardiac troponin, cTn) was intravenously administered to Sprague–Dawley rats for 4 weeks prior to coronary artery ligation. The results showed that myocardial-selective expression of hSLPI significantly reduced infarct size, cardiac troponin I (cTnI), creatine kinase-MB (CK-MB), and myoglobin levels that all served to improve cardiac function. Moreover, overexpression of hSLPI showed a reduction in inflammatory cytokines, oxidatively modified protein carbonyl (PC) content, ischemia-modified albumin (IMA), and necrosis and cardiac tissue degeneration. In conclusion, this is the first study to demonstrate cardiac-selective gene delivery of hSLPI providing cardioprotection against myocardial I/R injury in an in vivo model.

Anti-Protease Activity Deficient Secretory Leukocyte Protease Inhibitor (SLPI) Exerts Cardioprotective Effect against Myocardial Ischaemia/Reperfusion

Inhibition of proteases shows therapeutic potential. Our previous studies demonstrated the cardioprotection by the Secretory Leukocyte Protease Inhibitor (SLPI) against myocardial ischaemia/reperfusion (I/R) injury. However, it is unclear whether the cardioprotective effect of SLPI seen in our previous works is due to the inhibition of protease enzymes. Several studies demonstrate that the anti-protease independent activity of SLPI could provide therapeutic benefits. Here, we show for the first time that recombinant protein of anti-protease deficient mutant SLPI (L72K, M73G, L74G) (mt-SLPI) could significantly reduce cell death and intracellular reactive oxygen species (ROS) production against an in vitro simulated I/R injury. Furthermore, post-ischaemic treatment of mt-SLPI is found to significantly reduce infarct size and cardiac biomarkers lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB) activity, improve cardiac functions, attenuate I/R induced-p38 MAPK phosphorylation, and reduce apoptotic regulatory protein levels, including Bax, cleaved-Caspase-3 and total Capase-8, in rats subjected to an in vivo I/R injury. Additionally, the beneficial effect of mt-SLPI was not significantly different from the wildtype (wt-SLPI). In summary, SLPI could provide cardioprotection without anti-protease activity, which could be more clinically beneficial in terms of providing cardioprotection without interfering with basal serine protease activity.

Post-Ischemic Treatment of Recombinant Human Secretory Leukocyte Protease Inhibitor (rhSLPI) Reduced Myocardial Ischemia/Reperfusion Injury

Myocardial ischemia/reperfusion (I/R) injury is a major cause of mortality and morbidity worldwide. Among factors contributing to I/R injury, proteolytic enzymes could also cause cellular injury, expand the injured area and induce inflammation, which then lead to cardiac dysfunction. Therefore, protease inhibition seems to provide therapeutic benefits. Previous studies showed the cardioprotective effect of secretory leukocyte protease inhibitor (SLPI) against myocardial I/R injury. However, the effect of a post-ischemic treatment with SLPI in an in vivo I/R model has never been investigated. In the present study, recombinant human (rh) SLPI (rhSLPI) was systemically injected during coronary artery occlusion or at the onset of reperfusion. The results show that post-ischemic treatment with rhSLPI could significantly reduce infarct size, Lactate Dehydrogenase (LDH) and Creatine kinase-MB (CK-MB) activity, inflammatory cytokines and protein carbonyl levels, as well as improving cardiac function. The cardioprotective effect of rhSLPI is associated with the attenuation of p38 MAPK phosphorylation, Bax, caspase-3 and -8 protein levels and enhancement of pro-survival kinase Akt and ERK1/2 phosphorylation. In summary, this is the first report showing the cardioprotective effects against myocardial I/R injury of post-ischemic treatments with rhSLPI in vivo. Thus, these results suggest that SLPI could be used as a novel therapeutic strategy to reduce myocardial I/R injury.

SLPI - a Biomarker of Acute Kidney Injury after Open and Endovascular Thoracoabdominal Aortic Aneurysm (TAAA) Repair

Acute kidney injury (AKI) is a relevant complication following thoracoabdominal aortic aneurysm repair (TAAA). Biomarkers, such as secretory leucocyte peptidase inhibitor (SLPI), may enable a more accurate diagnosis. In this study, we tested if SLPI measured in serum is an appropriate biomarker of AKI after TAAA repair. In a prospective observational single-center study including 33 patients (51.5% women, mean age 63.0 ± 16.2 years) undergoing open and endovascular aortic aneurysm repair in 2017, SLPI was measured peri-operatively (until 72 h after surgery). After surgery, the postoperative complications AKI, as defined according to the KDIGO diagnostic criteria, sepsis, death, MACE (major cardiovascular events) and, pneumonia were assessed. In a subgroup analysis, patients with preexisting kidney disease were excluded. Of 33 patients, 51.5% (n = 17) of patients developed AKI. Twelve hours after admission to the intensive care unit (ICU), SLPI serum levels were significantly increased in patients who developed AKI. Multivariable logistic regression revealed a significant association between SLPI 12 hours after admission to ICU and AKI (P = 0.0181, OR = 1.055, 95% CI = 1.009-1.103). The sensitivity of SLPI for AKI prediction was 76.47% (95% CI = 50.1-93.2) and the specificity was 87.5% (95% CI = 61.7-98.4) with an AUC = 0.838 (95% CI = 0.7-0.976) for an optimal cut-off 70.03 ng/ml 12 hours after surgery. In patients without pre-existing impaired renal function, an improved diagnostic quality of SLPI for AKI was observed (Sensitivities of 45.45-91.67%, Specificities of 77.7-100%, AUC = 0.716-0.932). There was no association between perioperative SLPI and the incidence of sepsis, death, MACE (major cardiovascular events), pneumonia. This study suggests that SLPI might be a post-operative biomarker of AKI after TAAA repair, with a superior diagnostic accuracy for patients without preexisting impaired renal function.

Endothelial-Cell-Derived Human Secretory Leukocyte Protease Inhibitor (SLPI) Protects Cardiomyocytes against Ischemia/Reperfusion Injury

Vascular endothelial cell (EC)-derived factors play an important role in endothelial-cardiomyocyte crosstalk and could save cardiomyocytes (CMs) from injury. The manipulation of endothelial cells to secrete protective factors could enhance cardioprotection. Secretory leukocyte protease inhibitor (SLPI) has been known to protect the heart. The goal of this study was to evaluate the in vitro paracrine protective effect and mechanisms of EC-derived human SLPI on cardiomyocytes subjected to hypoxia/reoxygenation (H/R) injury. Stable endothelial cells overexpressing human SLPI were generated from an endothelial cell line (EA.hy926). The cytoprotective effect was determined by cell survival assay. The results showed that endothelial-derived recombinant human SLPI (rhSLPI) reduced simulated ischemia/reperfusion (I/R)-(81.75% ± 1.42% vs. 60.27% ± 2.52%, p < 0.05) and hypoxia/reoxygenation (H/R)-induced EC injury (83.57% ± 1.78% vs. 63.07% ± 1.93%, p < 0.05). Moreover, co-culture of ECs overexpressing rhSLPI with CMs at ratios 1:1 and 1:3 or treatment with conditioned medium enhanced cell viability by 10.51-16.7% (co-culture) and 15.25-20.45% (conditioned medium) by reducing intracellular reactive oxygen species (ROS) production, the Bax/Bcl-2 expression ratio, caspase-3, and caspase-8, and in preconditioned CMs by activation of p38 MAPK and Akt survival kinase. In conclusion, this study showed for the first time that EC-derived rhSLPI provided cardio-vasculoprotective effects against I/R injury as a possible alternative therapeutic strategy for cardioprotection.