BTP2, a Store-Operated Calcium Channel Inhibitor, Attenuates Lung Ischemia-Reperfusion Injury in Rats

Selective modulation of gene expression in activated normal human peripheral blood mononuclear cells by store-operated calcium entry blocker BTP2

Calcium is a critical signaling molecule in many cell types including immune cells. The calcium-release activated calcium channels (CRAC) responsible for store-operated calcium entry (SOCE) in immune cells are gated by STIM family members functioning as sensors of Ca2+ store content in the endoplasmic reticulum. We investigated the effect of SOCE blocker BTP2 on human peripheral blood mononuclear cells (PBMC) stimulated with the mitogen phytohemagglutinin (PHA). We performed RNA sequencing (RNA-seq) to query gene expression at the whole transcriptome level and identified genes differentially expressed between PBMC activated with PHA and PBMC activated with PHA in the presence of BTP2. Among the differentially expressed genes, we prioritized genes encoding immunoregulatory proteins for validation using preamplification enhanced real time quantitative PCR assays. We performed multiparameter flow cytometry and validated by single cell analysis that BTP2 inhibits cell surface expression CD25 at the protein level. BTP2 reduced significantly PHA-induced increase in the abundance of mRNAs encoding proinflammatory proteins. Surprisingly, BTP2 did not reduce significantly PHA-induced increase in the abundance of mRNAs encoding anti-inflammatory proteins. Collectively, the molecular signature elicited by BTP2 in activated normal human PBMC appears to be tipped towards tolerance and away from inflammation.

Store-operated calcium entry via ORAI1 regulates doxorubicin-induced apoptosis and prevents cardiotoxicity in cardiac fibroblasts

Despite exhibiting cardiotoxicity, doxorubicin (DOX) is widely used for cancer treatments. Cardiac fibroblasts (CFs) are important in the pathogenesis of heart failure. This necessitates the study of the effect of DOX on CFs. The impairment of calcium (Ca2+) homeostasis is a common mechanism of heart failure. Store-operated Ca2+ entry (SOCE) is a receptor-regulated Ca2⁺ entry pathway that maintains calcium balance by sensing reduced calcium stores in the endoplasmic reticulum. ORAI1, a calcium channel protein and the most important component of SOCE, is highly expressed in human cardiac fibroblasts (HCFs). It is upregulated in CFs from failing ventricles. However, whether ORAI1 in HCFs is increased and/or plays a role in DOX-induced cardiotoxicity remains unknown. In this study, we aimed to elucidate the relationship between ORAI1/SOCE and DOX-induced heart failure. Induction of apoptosis by DOX was characterized in HCFs. Apoptosis and cell cycle analyses were performed by fluorescence-activated cell sorting (FACS). Reactive oxygen species (ROS) production was measured using fluorescence. YM-58483 was used as an ORAI1/SOCE inhibitor. ORAI1-knockdown cells were established by RNA interference. In vivo experiments were performed by intraperitoneally injecting YM-58483 and DOX into mice. We first demonstrated that DOX significantly increased the protein expression level of p53 in HCFs by western blotting. FACS analysis revealed that DOX increased early apoptosis and induced cell cycle arrest in the G2 phase in fibroblasts. DOX also increased ROS production. DOX significantly increased the expression level of ORAI1 in CFs. Both YM-58483 and ORAI1 gene knockdown attenuated DOX-induced apoptosis. Similarly, YM-58483 attenuated cell cycle arrest in the G2 phase, and ORAI1 knockdown attenuated DOX-induced ROS production in HCFs. In the animal experiment, YM-58483 attenuated DOX-induced apoptosis. In HCFs, ORAI1/SOCE regulates p53 expression and plays an important role in DOX-induced cardiotoxicity. ORAI1 may serve as a new target for preventing DOX-induced heart failure.

Combination therapy of insulin-like growth factor I and BTP-2 markedly improves lipopolysaccharide-induced liver injury in mice

Acute liver injury is a common disease without effective therapy in humans. We sought to evaluate a combination therapy of insulin-like growth factor 1 (IGF-I) and BTP-2 in a mouse liver injury model induced by lipopolysaccharide (LPS). We chose this model because LPS is known to increase the expression of the transcription factors related to systemic inflammation (i.e., NFκB, CREB, AP1, IRF 3, and NFAT), which depends on calcium signaling. Notably, these transcription factors all have pleiotropic effects and account for the other observed changes in tissue damage parameters. Additionally, LPS is also known to increase the genes associated with a tissue injury (e.g., NGAL, SOD, caspase 3, and type 1 collagen) and systemic expression of pro-inflammatory cytokines. Finally, LPS compromises vascular integrity. Accordingly, IGF-I was selected because its serum levels were shown to decrease during systemic inflammation. BTP-2 was chosen because it was known to decrease cytosolic calcium, which is increased by LPS. This current study showed that IGF-I, BTP-2, or a combination therapy significantly altered and normalized all of the aforementioned LPS-induced gene changes. Additionally, our therapies reduced the vascular leakage caused by LPS, as evidenced by the Evans blue dye technique. Furthermore, histopathologic studies showed that IGF-I decreased the proportion of hepatocytes with ballooning degeneration. Finally, IGF-I also increased the expression of the hepatic growth factor (HGF) and the receptor for the epidermal growth factor (EGFR), markers of liver regeneration. Collectively, our data suggest that a combination of IGF-I and BTP-2 is a promising therapy for acute liver injury.

CYP2J2 and EETs protect against pulmonary arterial hypertension with lung ischemia-reperfusion injury in vivo and in vitro

Background

Cytochrome P450 epoxygenase 2J2 (CYP2J2) metabolizes arachidonic acid to epoxyeicosatrienoic acids (EETs), which exert anti-inflammatory, anti-apoptotic, pro-proliferative, and antioxidant effects on the cardiovascular system. However, the role of CYP2J2 and EETs in pulmonary arterial hypertension (PAH) with lung ischemia–reperfusion injury (LIRI) remains unclear. In the present study, we investigated the effects of CYP2J2 overexpression and exogenous EETs on PAH with LIRI in vitro and in vivo.

Methods

CYP2J2 gene was transfected into rat lung tissue by recombinant adeno-associated virus (rAAV) to increase the levels of EETs in serum and lung tissue. A rat model of PAH with LIRI was constructed by intraperitoneal injection of monocrotaline (50 mg/kg) for 4 weeks, followed by clamping of the left pulmonary hilum for 1 h and reperfusion for 2 h. In addition, we established a cellular model of human pulmonary artery endothelial cells (HPAECs) with TNF-α combined with anoxia/reoxygenation (anoxia for 8 h and reoxygenation for 16 h) to determine the effect and mechanism of exogenous EETs.

Results

CYP2J2 overexpression significantly reduced the inflammatory response, oxidative stress and apoptosis associated with lung injury in PAH with LIRI. In addition, exogenous EETs suppressed inflammatory response and reduced intracellular reactive oxygen species (ROS) production and inhibited apoptosis in a tumor necrosis factor alpha (TNF-α) combined hypoxia-reoxygenation model of HPAECs. Our further studies revealed that the anti-inflammatory effects of CYP2J2 overexpression and EETs might be mediated by the activation of PPARγ; the anti-apoptotic effects might be mediated by the PI3K/AKT pathway.

Conclusions

CYP2J2 overexpression and EETs protect against PAH with LIRI via anti-inflammation, anti-oxidative stress and anti-apoptosis, suggesting that increased levels of EETs may be a promising strategy for the prevention and treatment of PAH with LIRI.

Graphical Abstract

The Effects of Insulin-Like Growth Factor I and BTP-2 on Acute Lung Injury

Acute lung injury (ALI) afflicts approximately 200,000 patients annually and has a 40% mortality rate. The COVID-19 pandemic has massively increased the rate of ALI incidence. The pathogenesis of ALI involves tissue damage from invading microbes and, in severe cases, the overexpression of inflammatory cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). This study aimed to develop a therapy to normalize the excess production of inflammatory cytokines and promote tissue repair in the lipopolysaccharide (LPS)-induced ALI. Based on our previous studies, we tested the insulin-like growth factor I (IGF-I) and BTP-2 therapies. IGF-I was selected, because we and others have shown that elevated inflammatory cytokines suppress the expression of growth hormone receptors in the liver, leading to a decrease in the circulating IGF-I. IGF-I is a growth factor that increases vascular protection, enhances tissue repair, and decreases pro-inflammatory cytokines. It is also required to produce anti-inflammatory 1,25-dihydroxyvitamin D. BTP-2, an inhibitor of cytosolic calcium, was used to suppress the LPS-induced increase in cytosolic calcium, which otherwise leads to an increase in proinflammatory cytokines. We showed that LPS increased the expression of the primary inflammatory mediators such as toll like receptor-4 (TLR-4), IL-1β, interleukin-17 (IL-17), TNF-α, and interferon-γ (IFN-γ), which were normalized by the IGF-I + BTP-2 dual therapy in the lungs, along with improved vascular gene expression markers. The histologic lung injury score was markedly elevated by LPS and reduced to normal by the combination therapy. In conclusion, the LPS-induced increases in inflammatory cytokines, vascular injuries, and lung injuries were all improved by IGF-I + BTP-2 combination therapy.

IGF-1 Deficiency Rescue and Intracellular Calcium Blockade Improves Survival and Corresponding Mechanisms in a Mouse Model of Acute Kidney Injury

This study was undertaken to test two therapies for acute kidney injury (AKI) prevention, IGF-1, which is renal protective, and BTP-2, which is a calcium entry (SOCE) inhibitor. We utilized lipopolysaccharide (LPS) IP, as a systemic model of AKI and studied in five groups of animals. Three experiments showed that at 7 days: (1) LPS significantly reduced serum IGF-1 and intramuscular IGF-I in vivo gene therapy rescued this deficiency. (2) Next, at the 7-day time point, our combination therapy, compared to the untreated group, caused a significant increase in survival, which was noteworthy because all of the untreated animals died in 72 h. (3) The four pathways associated with inflammation, including (A) increase in cytosolic calcium, (B) elaboration of proinflammatory cytokines, (C) impairment of vascular integrity, and (D) cell injury, were adversely affected in renal tissue by LPS, using a sublethal dose of LPS. The expression of several genes was measured in each of the above pathways. The combined therapy of IGF-1 and BTP-2 caused a favorable gene expression response in all four pathways. Our current study was an AKI study, but these pathways are also involved in other types of severe inflammation, including sepsis, acute respiratory distress syndrome, and probably severe coronavirus infection.

The Blockade of Store-Operated Calcium Channels Improves Decompression Sickness in Rats

Background

Previous investigations reveal that BTP2, a store-operated calcium channel blocker, has protective and anti-inflammatory properties in multiple inflammatory diseases. This study investigates whether BTP2 can protect against decompression sickness (DCS) in a rat model.

Methods

BTP2 (2 mg/kg) was administered to male Sprague–Dawley rats 30 min before subjecting them to hyperbaric pressure. Control rats were not treated. After decompression, signs of DCS were examined, and samples of bronchoalveolar lavage fluid and lung tissue were obtained for evaluation.

Results

The incidence and mortality of DCS were decreased significantly in rats treated with BTP2 compared to those treated with dimethyl sulfoxide. BTP2 significantly attenuated DCS-induced lung edema, histological evidence of lung inflammation, necroptosis, and apoptosis, while it decreased levels of tumor necrosis factor alpha, interleukin-6, and cytokine-induced neutrophil chemoattractant-1 in bronchoalveolar lavage fluid. In addition, BTP2 reduced the expression of nuclear factor of activated T cells and early growth response protein 3 in lung tissue. BTP2 also significantly increased the levels of inhibitor kappa B alpha and suppressed the levels of nuclear factor kappa B in lung tissue.

Conclusion

The results suggest that BTP2 may has potential as a prophylactic therapy to attenuate DCS-induced injury.

Stromal-Interacting Molecule 1 (Stim1)/Orai1 Modulates Endothelial Permeability in Ventilator-Induced Lung Injury

Background

Increased endothelial permeability is involved in ventilator-induced lung injury (VILI). Stim1/Orai1 mediates store-operated Ca²⁺ activation, which modulates endothelial permeability. However, the underlying mechanisms of the Stim1/Orai1 pathway in VILI are poorly understood.

Material/Methods

Wistar rats were exposed to low tidal volume (7 mL/kg) or high tidal volume (40 mL/kg) ventilation. Human Lung Microvascular Endothelial Cells (HULEC) were subjected to 8% or 18% cyclic stretching (CS). BTP2 pretreatment was performed. Lung wet/dry weight ratio, histological changes of lung injury, and bronchoalveolar lavage fluid (BALF) protein were measured. Endothelial permeability and intracellular calcium concentration were evaluated in HULECs. Protein expression was determined by Western blotting.

Results

High tidal volume mechanical ventilation-induced lung injury (such as severe congestion and hemorrhage) and BTP2 pretreatment protected lungs from injury. The expression of Stim1, Orai1, and PKCα, lung wet/dry weight ratio, and BALF protein level significantly increased in the high tidal volume group compared to the control group and low tidal volume group. Importantly, BTP2 pretreatment alleviated the above-mentioned effects. Compared with exposure to 8% CS, the protein levels of Stim1, Orai1, and PKCα in HULECs significantly increased after exposure to 18% CS for 4 h, whereas BTP2 pretreatment significantly inhibited the increase (P<0.05). BTP2 pretreatment also suppressed increase of endothelial permeability and the intracellular calcium induced by 18% CS (P<0.05).

Conclusions

When exposed to high tidal volume or large-magnitude CS, Stim1 and Orai1 expression are upregulated, which further activates calcium-sensitive PKCα and results in calcium overload, endothelial hyperpermeability, and, finally, lung injury.

Ion Channels in Pulmonary Hypertension: A Therapeutic Interest?

Pulmonary arterial hypertension (PAH) is a multifactorial and severe disease without curative therapies. PAH pathobiology involves altered pulmonary arterial tone, endothelial dysfunction, distal pulmonary vessel remodeling, and inflammation, which could all depend on ion channel activities (K⁺, Ca²⁺, Na⁺ and Cl^-). This review focuses on ion channels in the pulmonary vasculature and discusses their pathophysiological contribution to PAH as well as their therapeutic potential in PAH.

MUTYH and ORAI1 polymorphisms are associated with susceptibility to osteoarthritis in the Chinese Han population

Background This study analyzed the associations between single nucleotide polymorphisms (SNPs) in the mutY homolog gene ( MUTYH) and the calcium release-activated calcium channel gene ( ORAI1) with susceptibility to osteoarthritis in the Chinese Han population. Methods A total of 350 patients diagnosed with osteoarthritis from October 2013 to May 2016 were selected as the study group, together with 350 age- and gender-matched healthy controls. MUTYH SNP rs3219463 and ORAI1 SNPs rs712853, rs12313273, rs6486795, rs12320939, and rs7135617 were analyzed by Sanger sequencing. Serum MUTYH levels were measured by enzyme-linked immunosorbent assay. The relationship between SNPs in MUTYH and ORAI1 and osteoarthritis susceptibility was analyzed and compared with the level of serum MUTYH in the osteoarthritis and control groups. Results MUTYH rs3219463 G allele carriers (GG or GA genotypes) and ORAI1 rs7135617 T allele carriers had a higher risk of osteoarthritis than patients with other genotypes. The level of serum MUTYH in the study group was significantly higher than in the control group (22.05 ± 19.14 ng/mL vs. 14.15 ± 13.54 ng/mL). Conclusions MUTYH and ORAI1 SNPs are associated with osteoarthritis susceptibility in the Chinese Han population.