The Effect of Lycium ruthenicum Murry Anthocyanins on the Apoptosis and Proliferation of H9c2 Cell Induced by Hypoxia

Based on the strong antioxidant activity of anthocyanins, this study was aimed to explore the potential infuence of Lycium ruthenicum Murry anthocyanins (LRMA) on hypoxia-induced apoptosis and proliferation of H9c2 rat cardiomyocytes. Te cell viability was frst tested after exposure to normoxia, hypoxia, and hypoxia+LRMA. After being incubated for 12h under normoxia and 24h under hypoxia in 50 μ g/mL LRMA or 100 μ M Salidroside, respectively, LDH content, cell morphology, and cell cycle progression were analyzed. In addition, cellular apoptosis along with the expression of B-cell lymphoma-2 (Bcl2) and BCL2-associated X (Bax) was explored. After that, RNA-seq and bioinformatics analysis revealed the lncRNAs-miRNAs-mRNAs ceRNA network related to hypoxia adaptation of H9c2 cells modulated by LRMA. Te fnal step was to detect the expression of cyclin T2 (CCNT2), cyclin-dependent kinase 9 (CDK9), and forkhead box P1 (FOXP1). Te results revealed that LRMA signifcantly attenuated the reduction of viability and protected H9c2 cells under hypoxic condition. In addition, LRMA not only restored the proliferation activity of H9c2 cells but also promoted apoptosis through stimulating Bcl2 enhancement and Bax inhibition induced by hypoxic stimulation. Tis study also identifed distinct pairs of ceRNA and the hypoxia-related diferentially expressed genes regulated by LRMA, including 862 lncRNAs (694 upregulated and 168 downregulated), 7 miRNAs (1 upregulated and 6 downregulated), and 351 mRNAs (226 upregulated and 125 downregulated). Te results also suggested that the hypoxia-related genes regulated by LRMA were mainly enriched in cell proliferation and division, cell energy metabolism, infammatory response, and cell development. However, LRMA could efectively promote the proliferation of H9c2 cells through enhancing CCNT2, CDK9, and FOXP1 under hypoxic conditions. Overall, LRMA could alleviate the proliferation inhibition and apoptosis in hypoxia-induced H9c2 cells.


Introduction
In 1947, Jack, who was studying at Bordeaux University in France, frst discovered a novel substance from the peanut skin and named it anthocyanin [1]. It is a water-soluble favonoid, which primarily exists in diferent forms in the cell fuid of a variety of plants, such as the fruits of Lycium ruthenicum Murry, seabuckthorn, black mulberry, blueberry, purple potato, and cherry [2]. It has been reported that anthocyanins can be found in diferent colors such as red, blue, and purple and can exist in acidic, alkaline, and neutral environments, respectively. Te six most common anthocyanidins identifed are pelargonidin, cyanidin, delphinium, peonidin, petunidin, and malvidin chloride [3]. More importantly, it has been found to be valuable in medical research for its characteristics of strong antioxidant, antiinfammatory, and antitumor activities [4][5][6] and its reported role in the prevention of the cardiovascular disease.
Lycium ruthenicum Murry is an undeveloped wild resource of medlar plant in the northwest of China, whose fruit is spherical, nontoxic, and sweet with purple black color, being famous as "Desert Black Pearl" and "King of anthocyanidin" for its rich anthocyanidins. It has been reported that the risk of cardiovascular disease can be efectively reduced by regular intake of the fruits and foods rich in anthocyanin [7]. In addition, negative correlation has been also reported between anthocyanin intake and the risk of myocardial infarction as well as cardiovascular diseaserelated mortality from epidemiological data [8], indicating that anthocyanin might play an important preventive role in cardiovascular disease.
Te heart is extremely sensitive to oxygen, so a high correlation has been reported between the occurrence and development of heart diseases and hypoxia [9]. Ischemia and hypoxia can efectively lead to cardiomyocyte injury and cardiac dysfunction, which have been assigned as the main reason of ischemic heart disease and sudden death [10]. Terefore, it is of great value to detect novel strategies to improve the hypoxic adaptability of cardiomyocytes. Furthermore, Wang et al. [11] found that cardiomyocyte injury induced by hypoxia could be markedly relieved through improving glucose metabolic rate by modulating lncRNA-XIST-miR-125b-Hexokinase2. In addition, Wang et al. [12] indicated that hypoxic injury of cardiomyocytes can be aggravated through autophagy mediated by lncRNA-MALAT1-miR-20b-Beclin1 axis. A number of prior reports have also demonstrated that hypoxia-induced cardiomyocyte injury can be regulated by lncRNAs-miRNAs-mRNAs ceRNA network. Herein, we have analyzed the potential efects of LRMA on hypoxic adaptation and constructed a network of lncRNAs-miRNAs-mRNAs to explore the mechanism of gene exchange and hypoxic protection regulated by LRMA in H9c2 cells. Te study aimed to lay a solid groundwork for the research on the adaptability of mammals in hypoxic environment and to provide a theoretical basis for application of LRMA in improving the hypoxic adaptation of mammals in the plateau.

Reagent Preparation.
Preparation of LRMA solution: accurately weigh 0.01 g of LRMA and dissolve it in 10 mL of DMEM medium. Prepare 1 mg/mL of LRMA master mix and store at −20°C.

Cell Culture.
H9c2 cells were cultured in DMEM at 37°C in the presence of 95% air and 5% CO 2 . Besides, H9c2 cells were cultured in DMEM at 37°C using hypoxic chambers with 1% O 2 , 94% N 2 , and 5% CO 2 for 24 h to build hypoxic model. According to the previous fndings of our research group, the optimal concentration of LRMA was 50 μg/ml. Terefore, subsequent experiments were carried out at this specifc concentration. H9c2 cells were counted in cell counting plates for application in diferent assays and then collected or analyzed accordingly.
2.5. LDH Activity Assay. H9c2 cells were planted in 96-well plates at 1 × 10 5 cells/well and cultured at 37°C with 95% air and 5% CO 2 for 24 h. Tereafter, 50 μg/mL LRMA was added for 12 h under normoxia + 24 h under hypoxic condition, and LDH activity was measured by using the LDH kit.
2.6. Cell Cycle Analysis. H9c2 cells were seeded in 6-well plates at 1 × 10 6 cells/well. Tis was followed by 50 μg/mL LRMA or 100 μM Sal treatment for 12 h under normoxia + 24 h under hypoxic condition, respectively. Te cells were then digested with trypsin and were fxed overnight in a 4°C refrigerator with 70% ethanol. After that, the cells were washed twice with PBS, resuspended by 500 μL staining solution (PI : RNase � 1 : 9), and incubated in dark for 30 min. Finally, cell cycle progression was detected by fow cytometry (BECKMAN COULTER, Xining, Qinghai, China).

Hoechst33342/PI Stain.
H9c2 cells were seeded in 6-well plates at 1 × 10 6 cells/well and cultured as described in 2.5. Te cells were then washed with PBS two times and stained with Hoechst 33342 and Propidium lodide (PI). Tereafter, the fuorescence of cells was detected by an inverted fuorescence microscope (Olympus IX83, Xining, Qinghai, China).

Analysis of ROS Accumulation.
H9c2 cells were seeded in 6-well plates at 1 × 10 6 cells/well and cultured as described above in 2.6. Tereafter, DCFH-DA was diluted 1000 times in the serum free medium and 10 μL of Rosup was added to the positive control group, followed by incubation for 30 min. After loading DCFH-DA fuorescent probe in situ, the cells were then washed twice to completely remove the unloaded probe and the fuorescence intensity was measured by fuorescent microplate reader (Bio-Rad, Xining, Qinghai, China). Te excitation wavelength was 502 nm and the emission wavelength was 530 nm.

Measurement of Apoptosis.
H9c2 cells were seeded in 6well plates at 1 × 10 6 cells/well and cultured as described above in 2.6. Te cells and supernatants were collected and resuspended in 500 μL bufer and stained with 5 μL annexin V and 5 μL PI for 10 min. Te apoptosis rate was detected by fow cytometry (BECKMAN COULTER, Xining, Qinghai, China).

RNA-Seq Analysis.
H9c2 cells were seeded in 6-well plates at 1 × 10 5 cells/well and cultured as described above in 2.5. Te total RNA was isolated from H9c2 cells by using Trizol reagent, and RNA-seq was performed.

Analysis of the Diferentially Expressed Genes.
Te diferentially expressed genes were compared between Hyp group and Hyp + LRMA group and Nor group and Hyp group. Ten, they were processed and analyzed by the edgeR package in R language version 4.0.2. Te signifcant differences in lncRNA, mRNA, and miRNA data were detected by logFC ≥ 1 and FDR < 0.05.

Metascape Pathway Enrichment Analysis.
Te pathway enrichment analysis of mRNA was performed by Metascape (online tools: https://metascape.org/gp/index. html). Te graphs in R language version 4.2.0 were created by ggplot2 package. Te signifcant diference in the results was tested by FDR < 0.05.

Interactions between miRNAs and mRNAs and between IncRNAs and miRNAs.
According to the expression of lncRNA, miRNA, and mRNA from RNA-seq, the possible correlation between lncRNAs and miRNAs and miRNAs and mRNAs was assessed by Pearson correlation analysis. After identifcation, it was correlated with both r > 0.8 and P < 0.05. Tereafter, correlations in both miRNAs-mRNAs and miRNAs-lncRNAs were predicted by TargetScan.

Construction of the Competing Endogenous RNA
(ceRNA) Network. Te competing endogenous RNA (ceRNA) network was constructed from the data obtained about the diferential expression of miRNAs, mRNAs, and lncRNAs. Te cross-linking relationship and network construction was performed by using Cytoscape version 3.8.2.
2.11. qRT-PCR. Total RNA was isolated from H9c2 cells by using Trizol reagent and then reversed transcription to cDNA in accordance with the manufacturer's instructions (Table 1). Te expression of miRNA was detected by tailing reaction. Te representative gene expression data were normalized with β-actin expression by using the following formula: 2 −△△ct . Te various constituents used for qRT-PCR are shown in Table 2.
PCR primers were as follows: ENSRNOT00000076766

Western-Blot Analysis.
H9c2 cells were seeded in 6-well plates at 1 × 10 6 cells/well. Te cells were then exposed to 50 μg/mL LRMA and 100 μM Sal incubation for 12 h under normoxia + 24 h under hypoxic condition, respectively. Te whole cell extract was prepared and quantifed by using the bicinchoninic acid (BCA) method as described previously [13] (Table 3).
Te proteins were then transferred to polyvinylidene fuoride (PVDF) membrane and then sealed with 5% skimmed milk at room temperature for 1.5 hours. Tereafter, PVDF membrane was washed with PBST for 3 minutes and this process was repeated for 5 times. Te membrane was then incubated with the primary antibody diluted at an appropriate concentration for overnight at 4°C. Next day, the membrane was washed with PBST for 10 minutes and this procedure was repeated for 5 times. After washing, diluted secondary antibody was added to the membrane and incubated at 37°C for 1 hour. After washing with PBST again slowly for 30 minutes (3 times), appropriate amount of prepared ECL luminescent solution was added to the PVDF flm, and it was incubated in the dark room for 1∼2 min. Te membrane was scanned and imaged with bio rad gel imager and obtained bands were analyzed with bio rad image analysis software (Quantity One ® 1-D Analysis Software), and the corresponding optical density values of the bands were recorded.

LRMA Mitigated Proliferation Reduction of H9c2 Cells and Played a Protective Role against Hypoxia.
We frst studied the protective efect of LRMA on H9c2 cells. Te results indicated that the viability of the cells treated with 25 and 50 μg/mL LRMA for 24, 36, and 48 h was signifcantly upregulated in normoxia (P < 0.05; Figure 1(a)). Figure 1(b) displays that compared with the normoxia group after hypoxia treatment, cell activity was signifcantly reduced (P < 0.05). Diferent concentrations of LRMA induced H9c2 rat cardiomyocytes for 24 h, 36 h, and 48 h signifcantly increased cell activity compared with the hypoxic group (P < 0.05), and the cardiomyocyte activity of H9c2 rats was increased after 12 h of induction, but the diference was not signifcant (P > 0.05). Comparison between concentration groups revealed that 50 μg/mLLRMA had the best efect in protecting cardiomyocyte activity in H9c2 rats, and comparison between time groups revealed that LRMA induced the best protective efect on cardiomyocytes in H9c2 rats for 36 h. Tis fnding suggested that the optimal strategy to protect the viability of H9c2 cells could be treating cells with 50 μg/mL LRMA for 12 h under normoxia + 24 h under hypoxic condition, and thus it was used for the subsequent experiments. Te next step was to observe LDH activity and cell morphology to examine whether the hypoxia model was constructed successfully or not. Figure 1(c) displays that hypoxia substantially elevated LDH activity (P < 0.01), whereas LRMA noticeably alleviated the LDH accumulation aroused by hypoxia (P < 0.05). Moreover, both the cell count and morphology were remarkably relieved by hypoxia but augmented upon LRMA treatment (Figure 1(d)). In addition, salidroside (Sal), one of the main components of Rhodiola, could also alleviate the observed efects of hypoxia.

LRMA Mitigated H9c2 Cell Apoptosis Promoted by
Hypoxia. We further explored the potential efect of LRMA on apoptosis in H9c2 cells under hypoxic condition and harvested the cells after the treatment. Interestingly, Figure 2(a) showed that H9c2 cells under hypoxic condition displayed notably brighter fuorescence, whereas LRMA treatment signifcantly reversed the fuorescence intensity aroused by hypoxia. Further study was performed next, which demonstrated that hypoxia remarkably augmented the ROS content, apoptosis rate, and Bax expression, but declined Bcl2 level and Bcl2/Bax ratio in H9c2 cells (P < 0.01). On the contrary in Hyp + LRMA and Hyp + Sal groups, the ROS content, apoptosis rate, and Bax expression were obviously lowered, but Bcl2 expression and Bcl2/Bax ratio were enhanced in Hyp + LRMA and Hyp + Sal groups (P < 0.01) (Figures 2(b)-2(e)). However, LRMA and Sal had exhibited no signifcant efect on cell apoptosis. Consequently, it was concluded that LRMA protected H9c2 cells by inhibiting apoptosis under hypoxic condition.

Identifcation of the Hypoxia-Related ceRNA Network
Regulated by LRMA. RNA-seq and bioinformatics analysis were performed to construct the hypoxia-related ceRNA network and to explore the target axis of hypoxia injury and the potential molecular mechanisms of hypoxia adaptation in H9c2 cells afected by LRMA.
Te results indicated that there were 1404 diferentially expressed lncRNAs (525 upregulated and 879 downregulated), 20 miRNAs (12 upregulated and 8 downregulated), and 829 mRNAs (609 upregulated and 220 downregulated). Tese were controlled primarily by hypoxia       Tables 1-3 of supplementary materials, respectively). Ten, hierarchical cluster analysis was performed to explore the possible phenotypic diferences of transcriptome regulated by LRMA under the hypoxic conditions. Te diferentially expressed lncRNAs, miRNAs, and mRNAs indicated that there were obvious diferences in Norm group, Hyp group, and Hyp + LRMA group, but some of them were similar while others were diferent in Norm group and Hyp + LRMA group (Figures 3(a)-3(c)). Figure 3 and Table 1 exhibit that there were 12 specifc pathway enrichment projects of diferentially expressed mRNA, including heatmap and Venn of lncRNA (Figure 3(a)), miRNA (Figure 3(b)), and mRNA (Figure 3(c)) were constructed. In addition, the bubble chart of pathway enriched by metascape (https://metascape.org/ gp/index.html) was plotted (Figure 3(d)). Furthermore, ceRNA network was also built by cytoscape_v3.8.2 (Figure 3(e)). N � 3. However, hypoxia-related genes regulated by LRMA were mainly enriched in cell proliferation and division (regulation of multicellular organization growth, brain derived neurotrophic factor (BDNF) signaling pathway, Ras signaling pathway, Raf/MAP kinase cascade, and the regulation of ERK1 and ERK2 cascade and MAPK signaling pathway). Tey were also enriched in the cell energy metabolism (MAPK signaling pathway, cellular ketone metabolic process, regulation of steroid biosynthetic process, regulation of lipid biosynthetic process, and the positive regulation of cold induced thermogenesis), infammatory response (response to lipopolysaccharide), and cell development (morphogenesis of embryonic skeletal system) ( Table 6). Terefore, we speculated that hypoxia adaptation of H9c2 cells might be regulated by LRMA     Journal of Food Biochemistry through modulation of the cell proliferation and division, cell energy metabolism, infammatory response, and cell development. ceRNA can regulate the expression of the various gene transcripts by competing for reaction elements bind to the same miRNA. We did screening parameters: correlation ≥0.6 and P value ≤0.05. Tereafter, lncRNAs-miRNAs-mRNAs regulatory network was constructed by Pearson correlation analysis and targetscan database prediction. Finally, 8 lncRNA-miRNA pairs and 33 miRNA-mRNA pairs were obtained (showed in the list 10 of supplementary materials (available here)), and 5 pairs of lncRNAs-miRNAs-mRNAs (ENSRONG09184-ASL-rno-miR-98-6p-FOXP1, AABR0758158.1-217-rno-miR-98-6p-FOXP1, AABR0758158.1-217-rno-miR-29c-3p-FOXP1, AABR0758158.1-217-rno-miR-29c-3p-CCNT2, and Pspc1-204-rno-miR-29c-3p-CCNT2) were analyzed (Figure 3(e)). Te expression of the most signifcant key nodes in the ceRNAs network was assessed by qRT-PCR (Pspc-1-204, AABR07058158.1-217, miR-98-5p, miR-29c-3p, CCNT2, and FOXP1). Te results of qRT-PCR and highthroughput sequencing were found to be completely consistent in the expression patterns (Figures 4(a)-4(c)), thus indicating that key genes in the ceRNAs regulatory network regulated by LRMA were objective and reliable. CCNT2, a highly conserved member of cyclin family, can regulate the activity of cyclin dependent kinase. It is periodically expressed in the cell cycle and signifcantly correlated with myocardial ischemia reperfusion, acute myeloid leukemia, cancer, acute nephropathy, and other diseases [13][14][15][16]. Furthermore, CCNT2 and CDK9 can substantially promote the translation and form heterodimer by phosphorylating the C-terminal of the large subunit in RNA polymerase II and activating the positive transcription elongation factor b (p-TEFb) to accelerate the cell cycle progression [17]. On the other hand, by combining DNA with its conserved forkhead DNA binding domain, FOXP1, a transcription factor, it can infuence the cell proliferation, diferentiation, and metabolic pathways, such as embryonic stem cell pluripotency, cardiomyocyte proliferation, neuronal activity, and glucose homeostasis [18]. FOXP1 has been reported to be expressed in the whole heart, including myocardium, endocardium, and endocardial cushion [19]. However, it plays an extremely pivotal role in the regulation of the proliferation, diferentiation, and angiogenesis of heart [20]. In this study, we found that LRMA efectively protected the proliferative activity of H9c2 cells aroused by hypoxia, which may be interrelated to these 5 pairs of ceRNAs. In addition, LRMA dramatically enhanced expression of CCNT2 and FOXP1 under hypoxic condition. Terefore, we speculated that LRMA might protect the proliferative activity and hypoxic adaptability of H9c2 cells under hypoxic condition by CCNT2 and FOXP1. Based on the result of RNA-seq, further study was performed by analyzing the expression of both CCNT2 and FOXP1. Figures 4(d) and 4(e) show that hypoxia markedly declined the CCNT2, CDK9, and FOXP1 expression in H9c2 cells (P < 0.01). On the contrary, in H9c2 cells stimulated by hypoxia, LRMA substantially increased the CCNT2, CDK9, and FOXP1 expression. In addition, under hypoxic conditions (P > 0.05), the regulation of CCNT2, CDK9, and FOXP1 expression in H9c2 cells by LRMA and Sal was not found to be signifcantly diferent.

Discussion
Cell proliferation is the basis for growth, development, reproduction, and genetics of organisms, and the traditional concept is that cardiomyocytes are terminally diferentiated cells that cease to participate in the cell cycle process shortly after birth and no longer have the ability to proliferate [21,22], but it has been found that cardiomyocyte proliferation after myocardial injury is a necessary process for restoring myocardial function [23], so it is particularly important to protect the proliferative activity of cardiomyocytes induced by hypoxia. Anthocyanins are watersoluble natural pigments with good antioxidant activity, which can efectively alleviate hypoxia-induced cardiomyocyte apoptosis and myocardial damage. However, no study has been reported on the efects of LRMA on hypoxiainduced proliferation and apoptosis in H9c2 rat cardiomyocytes.
In this study, the efect of LRMA on the proliferation viability of H9c2 rat cardiomyocytes under hypoxia was investigated for the frst time. It was found that the addition of LRMA signifcantly increased the activity of H9c2 rat cardiomyocytes induced by 25 and 50 μg/mL LRMA for 24, 36, and 48 h under normoxic conditions and that 100 μg/mL LRMA induced H9c2 rat cardiomyocytes for 24 h was able to signifcantly increase the activity of H9c2 rat cardiomyocytes. Under hypoxic conditions, diferent concentrations of LRMA induced in H9c2 rat cardiomyocytes for 12, 24, 36, and 48 h could efectively improve the H9c2 rat cardiomyocyte activity, indicating that LRMA could efectively protect the cell proliferation activity of H9c2 rat cardiomyocytes under hypoxic conditions, among which 50 μg/mL LRMA induced for 36 h had the best protective efect on H9c2 rat cardiomyocyte activity. Based on the above results, the optimal induction protocol for LRMA under hypoxic conditions was screened as follows: 50 μg/mL LRMA pretreatment for 12 h, while the cells were then placed under hypoxic + LRMA conditions and continued to be induced for 24 h.
Sal has various efects such as good antioxidant and free radical scavenging [24] and protective efect on myocardial ischemia [25], so it was used as a positive control group in this experiment to compare and test the efect of LRMA on hypoxia-induced proliferation and apoptosis of H9c2 rat cardiomyocytes. In this experiment, it was found using fow cytometry that LRMA could effectively alleviate the cell cycle arrest of H9c2 rat cardiomyocytes under hypoxic conditions and promote cell cycle progression, thus promoting the proliferation of H9c2 rat cardiomyocytes. Under hypoxic conditions, there was no signifcant diference between LRMA and Sal in promoting H9c2 cell proliferation. In summary, LRMA can regulate the proliferation of H9c2 cells and protect these cells under hypoxic conditions. Under hypoxic conditions, the LDH content in the cytosol increases, cells undergo morphological changes such as crumpling and deformation, and the cell structure, i.e., the integrity of the cell membrane and normal cell morphology, is damaged. Te results of the present experimental study showed that hypoxia caused reduced membrane integrity, destruction of cell morphology and structure, and apoptotic and necrotic morphology in H9c2 rat cardiomyocytes, which is consistent with the results of the previous studies [26,27]. Apoptosis is a programmed cell death that is complexly regulated by multiple genes and involves activation, expression, and regulation of intracellular-related factors, which have important roles in immune defense and cell damage in animal organisms [28,29]. Te apoptotic process is regulated by several genes, among which the Bcl2 family genes are predominant [30]. Bcl2 and Bax belong to the Bcl2 family with diferent roles to inhibit and promote apoptosis, respectively. Bcl2 is a representative of apoptosis-inhibiting genes, which can inhibit apoptosis by antagonizing the expression of proapoptotic genes [31]. Bax is a homologue of Bcl2, which binds to Bcl2 to form a heterodimer and then initiates a signaling pathway to promote apoptosis. Bax can antagonize the inhibitory efect of Bcl2 and promote apoptosis, and the ratio of Bax/Bcl2 expression can also refect apoptosis [32]. Mitochondrial aerobic respiration is the main source of endogenous ROS [33], and hypoxia can lead to the production of large amounts of ROS in cells, which, if not cleared in time, can damage the body's natural antioxidant system and can directly damage cardiomyocytes, protein structures, and DNA and induce apoptosis in cardiomyocytes by upregulating Bcl2 and downregulating Bax expression, thus causing hypoxic body damage and thus afecting the structure and function of the heart [34,35]. In this experiment, we found that LRMA could efectively inhibit hypoxiainduced ROS content accumulation and apoptosis in H9c2 rat cardiomyocytes and could downregulate the mRNA and protein expression of Bax and upregulate Bcl2 and Bcl2/Bax ratio to inhibit hypoxia-induced apoptosis in H9c2 rat cardiomyocytes under hypoxic conditions, and the inhibitory efect of LRMA on hypoxia-induced apoptosis in H9c2 rat cardiomyocytes under hypoxic conditions was not signifcantly diferent from that of Sal. Most ceRNAs can bind to miRNA by their potential microRNA response elements (MREs) [36]. A number of prior studies have reported that ceRNAs can afect the downstream signal pathway by regulating the number or the function of diferent miRNAs [37,38]. Te lncRNAs-miRNAs-mRNAs regulatory network, a hot research topic in several felds, can efectively participate in immune regulation, cardiovascular diseases or other important biological processes [39][40][41]. Besides, various studies have shown that lncRNAs-miRNAs-mRNAs regulatory network can play a protective role in myocardial injury induced by hypoxia. Terefore, we investigated the efect of LRMA on hypoxiainduced mammalian myocardial injury by constructing a hypoxia-related lncRNAs-miRNAs-mRNAs ceRNA network of H9c2 cells regulated by LRMA.
By using RNA-seq technique and biological information analysis, 862 hypoxia-related diferentially expressed lncRNAs, 7 miRNAs, and 351 mRNAs were found to be involved in the regulation of LRMA. To predict the function of lncRNAs, this study performed functional enrichment analysis of the source genes involved in the regulation of hypoxia-related diferentially expressed lncRNAs in H9c2 rat cardiomyocytes, and the results showed that the hypoxiarelated genes regulated by LRMA were mainly enriched in cell proliferation and division, cell energy metabolism, infammatory response, and cell development. Te above functions and pathways may be potential pathways involved in the regulation of LRMA-mediated lncRNAs in hypoxiainduced H9c2 rat cardiomyocytes. Finally, we obtained fve diferent pairs of ceRNAs i.e., ENSRONG09184-ASL-rno-miR-98-6p-FOXP1, AABR0758158.1-217-rno-miR-98-6p-FOXP1, AABR0758158.1-217-rno-miR-29c-3p-FOXP1, AABR0758158.1-217-rno-miR-29c-3p-CCNT2, Pspc1-204rno-miR-29c-3p-CCNT2, and the qRT-PCR validation results were consistent with the RNA-seq results, indicating that under hypoxic conditions, LRMA signifcantly regulates the key genes CCNT2 and FOXP1 mRNA expression under hypoxic conditions. Te heterodimer formed by CCNT2/CDK9 has been reported to be functionally distinct from other CDK/cyclin complexes that can regulate cell cycle processes but maintains structural afnity with these complexes. CCNT2/CDK9 promotes gene transcription extension, cell proliferation, diferentiation, and inhibits apoptosis [42]. It was shown that in mouse embryonic stem cells, attenuation of CCNT2/CDK9 inhibits muscle cell proliferation [43]. FOXP1, a member of the P subfamily of the FOX transcription factor superfamily, can efectively promote cardiomyocyte proliferation and myocardial remodeling [44]. In addition, degradation of FOXP1 enhances cellular infammatory responses and hypoxia-induced injury [45]. In this experiment, we found that LRMA could alleviate the cell cycle arrest of H9c2 rat cardiomyocytes under hypoxic conditions and promote the proliferation of H9c2 rat cardiomyocytes by increasing the mRNA and protein level expression of CCNT2, CDK9, and FOXP1 in hypoxia-induced H9c2 rat cardiomyocytes. And the regulatory efect of LRMA on hypoxia-induced proliferation of H9c2 rat cardiomyocytes under hypoxic conditions was not signifcantly diferent from that of Sal. Te above results suggest that LRMA may promote hypoxia-induced proliferative efects in H9c2 rat cardiomyocytes through the regulation of lncRNAs-related ceRNA coregulatory network, but the related molecular mechanisms need to be further validated.

Conclusions
In this study, the efect of LRMA on the proliferation and apoptosis of H9c2 rat cardiomyocytes under hypoxia was investigated for the frst time, and the optimal induction protocol of LRMA under hypoxic conditions was screened: 50 μg/mL LRMA pretreatment for 12 h, and the cells were then placed under hypoxia + LRMA conditions for 24 h. LRMA was able to promote hypoxia-induced proliferation and inhibit apoptosis in H9c2 rat cardiomyocytes, efectively protecting the cellular activity of H9c2 rat cardiomyocytes under hypoxic conditions. Tis study also found that LRMA may promote the proliferative efect of hypoxia-induced H9c2 rat cardiomyocytes through regulating the coregulatory network of 5 pairs of lncRNAs-related ceRNAs, but the related molecular mechanisms need to be further verifed ( Figure 5).