HF constitutes the advanced phase of various cardiovascular disorders, such as cardiomyocyte injury and death, fibrosis and hypertrophy, inflammation reactions, neuroendocrine imbalance, etc. The management of HF predominantly involves symptomatic and neuroendocrine therapeutic approaches. Among them, neuroendocrine therapies, such as ACEI/ARB, β-blockers and aldosterone receptor antagonists, have been scientifically demonstrated to improve the prognosis of HF patients. However, the 5-year survival rate for HF patients remains suboptimal(17). Exploration of new intervention targets, pathways, and treatment methods for HF is necessary.
In the development of HF, autophagy dysfunction can lead to cardiomyocyte apoptosis, inflammatory response, and metabolic disorder, thus promoting the progression of HF. Currently, there is increasing research on the mechanism of HF and autophagy. Research has shown that in elderly mice, the insulin-like growth factor 1 receptor (IGF1R) can inhibit autophagic flux in the heart, leading to an increase in hypertrophic cardiomyocytes and hindering the recovery of heart function. However, low IGF1R activity can consistently improve aging heart function and myocardial bioenergetics in an autophagy-dependent manner. The IGF1R exhibits higher signal activity in HF of humans(18). In I/R injury, during ischemia, insufficient nutrient supply to myocardial cells can activate autophagy through AMPK, thereby maintaining energy production and promoting survival of myocardial cells during ischemia. However, prolonged ischemia can also suppress autophagic flux(19). During the reperfusion phase, autophagy flux can be restored, while the recovery of oxygen results in a noteworthy rise in the generation of ROS which also stimulates autophagy flux in cardiomyocytes and reduces cardiomyocytes loss and acute I/R injury(20). Every coin has two sides, the increase of ROS can also lead to an increase in BECLIN 1 expression, which will activate autophagic flux. This activation of autophagic flux is harmful and can lead to an increase in I/R injury(19). In pressure overload-induced HF, autophagy flux is also increased, and its role is both beneficial and harmful. When stressed, increased autophagy flux can exacerbate the production of myocardial fibrosis, leading to myocardial hypertrophy(21). On the contrary, there are studies proving that autophagy serves as an adaptive response to stress overload, during which AMPK or metformin can enhance autophagic response, thereby reducing myocardial hypertrophy(22). The above mechanisms elucidate that autophagy is an complicated process that exhibits notable dynamism. The regulation of autophagy, either up or down, is largely contingent upon the environmental factors that tissue cells encounter. The degree of adjustment can also lead to different outcomes, which poses many challenges for related research.
Our analysis commences at the level of gene, offering potential insights for subsequent research endeavors. Based on the GSE 57338 dataset and 803 ARGs, we employed the R package "limma" to screen for differentially expressed genes and ultimately identified 4 key genes via a series of algorithms and subsequent verification processes.
TPCN1 (Two Pore Segment Channel 1) is a gene that encodes for a protein called two-pore channel 1. This protein belongs to the family of two-pore channels, which are ion channels found within the endolysosomal system of cells(23). TPCN1 is very important in regulating calcium ion homeostasis and lysosomal function, and has been linked to various physiological processes such as autophagy, apoptosis, and viral infection. The presence of TPC1 and TPC2 is critical to maintaining proper levels of basal and induced autophagy in cardiomyocytes. On the contrary, the lack of these proteins can lead to a decrease in cell viability under stressful conditions(24). Studies on the mechanism of TPCN1 in HF are not in-depth, but its effect on cardiomyocytes and its relationship with autophagy can furnish different directions on exploring HF.
The gene MAP2K1, responsible for encoding the MAP kinase kinase protein, belongs to the category of dual specificity protein kinases. This protein actively participates in the phosphorylation cascade of the mitogen-activated protein (MAP) kinase pathway. MAP kinases are integral to numerous cellular processes including cell proliferation, differentiation, survival, and apoptosis. MAP2K1 is also known as MEK1. In the signaling hierarchy of a cardiac myocyte, the MEK1-ERK1/2 pathway is likely to hold a central regulatory position(25). In a myocardial ischemia-reperfusion model, the activation of ERK1/2 has been found to reduce apoptosis caused by reperfusion injury, indicating that the MAP2K1 signaling pathway may provide cardioprotective effects(26). Furthermore, the Raf/MEK/ERK pathway is capable of regulating the expression levels of LC3B and SQSTM1/p62 within cells, which act as important markers for autophagy within cells(27).
S100A9(S100 calcium binding protein A9) encodes for a protein called S100A9 or Calgranulin B which is expressed by various cells of the immune system and is involved in a range of biological processes, including chemotaxis, antimicrobial activity, and cell signaling. The translocation of S100A9 to the nucleus allows for the regulation of MDSC differentiation by IL-10 secreted by macrophages, thereby achieving the role of protecting against HF(28). In addition, S100A9 can directly induce autophagy and apoptosis(29, 30).
CD38 (CD38 molecule) encodes for a non-lineage-restricted, type II transmembrane glycoprotein and it also functions as an enzymatic ectoenzyme. CD38 knockout mice were observed to have a protective effect on the heart when subjected to ischemic/reperfusion injury. This protective mechanism operates through the activation of the antioxidative stress pathway mediated by SIRT1/FOXOs. CD38 also serves as a crucial factor in cardiac hypertrophy by inhibiting SIRT3 expression and activating the Ca2+-NFAT signaling pathway(31). Research has shown that overexpression of CD38 can downregulate the expression of Rab7 and its adaptor protein, pleckstrin homology domain-containing protein family member 1 (PLEKHM1). The loss of Rab7/PLEKHM1 impairs autophagosome-lysosome fusion, which leads to a blockade of autophagy flux and results in heart dysfunction under H/I conditions. These findings indicate that targeted inhibition of CD38 overexpression could be a promising therapeutic strategy(32).
Moreover, we performed enrichment analysis on 15 AR-DEGs. The results showed that significantly enriched GO terms were “regulation of cell growth”, “inflammatory response”, and “regulation of transport”, and signal pathways, such as “IL-17 signaling pathway”, “NOD-like receptor signaling pathway” and so on. Autophagy serves as a mechanism for clearing out dysfunctional or unnecessary materials within the cell and recycling them for energy production and the maintenance of cellular homeostasis, so it is essential in regulating cell growth and coping with various stresses such as starvation, infection, and inflammation(33). IL-17 (Interleukin-17) plays a vital role in regulating cardiac disorders. The concentration of IL-17 in the blood plasma was determined to be significantly elevated amongst individuals with HF in comparison to those without the condition. A negative correlation was found between the IL-17 levels and cardiac ejection fraction as well as fractional shortening. An increase in IL-17 disrupts calcium handling and cardiac remodeling via the NF-κB pathway, leading to impaired cardiac function. Inhibiting the IL-17 signaling pathway may become a potential treatment method for heart failure(34). In addition, IL-17 triggers autophagy by activating the ERK1/2-Beclin-1-p62 pathway, while suppresses through the BCL2-Beclin-1 and PI3K-GSK3β pathways. Conversely, autophagy suppresses IL-17 production by activating p38 MAPK signaling(35). The NOD-like receptor (NLR) signaling pathway is an essential factor within the innate immune system that detects and responds to microbial infection and cellular damage. NLRs are a group of endogenous cytosolic sensors responsible for detecting pathogen-related molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs). When activated, these receptors trigger a signaling cascade that ultimately leads to the secretion of pro-inflammatory cytokines, chemokines, and antimicrobial peptides(36). Many literatures indicated the NLR signaling pathway exerted a strong effect in the heart(37, 38). The vital role of the NLR pathway and its binding autophagy-related pathways in the pathological development of HF has been extensively studied(39, 40). These studies have offered insights that can be used to delve into the mechanistic aspects of autophagy-related HF.
Utilizing single-sample GSEA (ssGSEA), we investigated the extent of immune infiltration present in each sample according to a total of 28 immune cell types. Various T cells, including activated CD4 T cells, activated CD8 T cells, effector memory CD4 T cells, and Type 2 T helper cells, are positively correlated with the progression of HF, providing insight into the role of immune genes in the disease.
In addition, we constructed TF-gene regulatory networks and predicted target drugs, such as Cyclosporine and Estradiol based on 4 key genes of HF, which further expanded the scope of research and offered valuable insights for the development of novel drugs and precise clinical targeting therapies for HF.
This study has certain limitations for it relies on the transcriptome information that is publicly accessible in databases. In addition, integrating the findings of this investigation with single-cell sequencing and advancements in multi-omics research is imperative. In future research endeavors, a more in-depth analysis should be conducted on the molecular mechanisms of the 4 pivotal genes. This analysis will be utilized to explore the diagnostic and prognostic potential of these genes, as well as enhance our comprehension of autophagy-related mechanisms involved in HF.