CARDIOVASCULAR JOURNAL OF AFRICA • Volume 33, No 6, November/December 2022 AFRICA 307 surgery group (3.70 ± 0.67) compared with that in the control group (0.30 ± 0.48). VASs of VRP-pretreated groups (group 3: 1.70 ± 0.67 vs 3.70 ± 0.67, p < 0.01; group 4: 1.40 ± 0.52 vs 3.70 ± 0.67, p < 0.01) were significantly decreased compared with those of group 2 (3.70 ± 0.67) (Fig. 2A). Number of rats that presented with AVBs Type I and II second-degreeAVBs occurred in the VRP-pretreated model groups. Third-degree AVB did not occur in the two VRP-pretreated surgery groups. Type I second-degree AVBs occurred in four out of 10 rats in group 3 and six out of 10 rats in group 4. Type II second-degree AVBs were present in five out of 10 rats in group 3 and eight out of 10 rats in group 4 (Fig. 2B). Identification of DEGs A total of 1 433 DEGs were identified, of which 36 were upregulated and 1 397 were downregulated. Volcano plots were used to demonstrate integral gene expression variation between low- and high-dose VRP-pretreated (0.5 and 1 mg/kg, respectively) rat hearts after TAC surgery (Fig. 3). The top 10 up- and downregulated DEGs are shown in Table 1A and B. Hierarchical cluster analysis of the top 100 DEGs among three randomly selected rats in groups 2 and 4 are shown in Fig. 4. The expression heat map of the top 100 DEGs could effectively function as a biomarker and target of anti-arrhythmic effects of VRP related to pressure overload. GO and KEGG pathway analyses The top 10 most enriched GO terms of up- and downregulated DEGs between groups 2 and 4 for biological processes (BPs), cellular components (CCs), and molecular functions (MFs) Table 1. Top 10 up- and downregulated DEGs A. The top 10 upregulated DEGs Gene Log 2(fold change) p-value LOC102723236 1.25960218 0 Rmrp 1.46606767 2.65E-237 Nppa 1.86134455 1.44E-96 Nppb 1.77349742 3.55E-33 Hbb 1.63335752 3.23E-27 Tnnc1 1.27125195 5.72E-27 Rps21 1.84461994 8.54E-21 LOC100134871 2.4277748 1.22E-18 Ndufb9 1.39795852 2.00E-16 Rpl37a-ps1 1.41753224 3.41E-16 B. The top 10 downregulated DEGs Gene Log 2 (foldchange) p-value Trnm –1.4951322 0 LOC103692592 –2.9743556 0 Trnl1 –3.5924716 0 LOC102547101 –1.651693 0 Fth1 –1.8826853 0 LOC310926 –2.6822775 0 LOC102553290 –3.902779 0 Trnn –1.3458582 3.65E-307 Hspb7 –2.4361902 8.59E-254 Hspb6 –3.257822 5.77E-246 DEGs, differentially expressed genes; log 2(fold change) = log 2[mean expression ratio (group 4/group 2)]. –4 –2 –1 0 1 2 4 log 2 (fold change) –log10 (Q-value) 15 10 5 1.3 0 gene down: 1 397 gene up: 36 Fig. 3. Volcano plot of gene expression alterations among three randomly selected rats in each group (groups 2 and 4). The threshold values were log 2(fold change) > 1 and p < 0.05. The red and green dots represent upregulated and downregulated genes, respectively. The black dots indicate genes with no statistically significant difference. Table 2. Top 10 GO-BP analysis of DEGs between groups 2 and 4 Term Description Count p-value GO:0045449 Regulation of transcription 204 3.35E-23 GO:0051252 Regulation of RNA metabolic process 164 1.23E-19 GO:0006355 Regulation of transcription, DNA-dependent 159 1.00E-18 GO:0045935 Positive regulation of nucleobase, nucleoside, nucleotide and nucleic acid metabolic process 100 1.98E-18 GO:0010557 Positive regulation of macromolecule biosynthetic process 102 2.10E-18 GO:0006357 Regulation of transcription from RNA polymerase II promoter 99 3.83E-18 GO:0045941 Positive regulation of transcription 91 8.59E-18 GO:0010628 Positive regulation of gene expression 92 1.31E-17 GO:0051173 Positive regulation of nitrogen compound metabolic process 100 1.52E-17 GO:0031328 Positive regulation of cellular biosynthetic process 103 3.30E-17 GO: gene ontology; BP: biological processes; DEGs: differentially expressed genes. Table 3. Top 10 GO-CC analysis of DEGs between groups 2 and 4 Term Description Count p-value GO:0031981 Nuclear lumen 108 1.81E-11 GO:0005829 Cytosol 122 5.21E-11 GO:0044451 Nucleoplasm part 61 7.01E-10 GO:0043233 Organelle lumen 126 9.10E-10 GO:0031974 Membrane-enclosed lumen 127 2.62E-09 GO:0070013 Intracellular organelle 121 2.87E-09 GO:0000267 Cell fraction 103 9.34E-09 GO:0005654 Nucleoplasm 81 1.06E-08 GO:0045121 Membrane raft 31 2.20E-08 GO:0005901 Caveola 17 1.13E-07 GO: gene ontology; CC: cellular component; DEGs: differentially expressed genes.
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