Transcriptomic Analysis of Long Noncoding RNA and mRNA Expression Profiles in the Amygdala of Rats with Bone Cancer Pain-Depression Comorbidity

Epigenetic mechanisms of bone cancer pain

The management and treatment of bone cancer pain (BCP) remain significant clinical challenges, imposing substantial economic burdens on patients and society. Extensive research has demonstrated that BCP induces changes in the gene expression of peripheral sensory nerves and neurons, which play crucial roles in the onset and maintenance of BCP. However, our understanding of the epigenetic mechanisms of BCP underlying the transcriptional regulation of pro-nociceptive (such as inflammatory factors and the transient receptor potential family) and anti-nociceptive (such as potassium channels and opioid receptors) genes remains limited. This article reviews the epigenetic regulatory mechanisms in BCP, analyzing the roles of histone modifications, DNA methylation, and noncoding RNAs (ncRNAs) in the expression of pro-nociceptive and anti-nociceptive genes. Finally, we provide a comprehensive view of the functional mechanisms of epigenetic regulation in BCP and explore the potential of these epigenetic molecules as therapeutic targets for BCP.

Characterization of a Cancer-Induced Bone Pain Model for Use as a Model of Cancer Cachexia

Cancer cachexia is a debilitating syndrome characterized by progressive weight loss, muscle wasting, and systemic inflammation. Despite the prevalence and severe consequences of cancer cachexia, effective treatments for this syndrome remain elusive. Therefore, there is a greater need for well-characterized animal models to identify novel therapeutic targets. Certain manifestations of cachexia, such as pain and depression, have been extensively studied using animal models of cancer-induced bone pain (CIBP). In contrast, other aspects of cachexia have received less attention in these models. To address this issue, we established the CIBP model by injecting Lewis lung carcinoma into the intramedullary cavity of the femur, observed cachexia-related symptoms, and demonstrated the utility of this model as a preclinical platform to study cancer cachexia. This model accurately recapitulates key features of cancer cachexia, including weight loss, muscle atrophy, adipose tissue depletion, CIBP, and anxiety. These findings suggest that psychological factors, in addition to physiological and metabolic factors, play significant roles in cancer cachexia development. Our model offers a valuable resource for investigating the underlying mechanisms of cancer cachexia and for developing innovative therapeutic strategies that target physical and psychological components.

LncRNA 51325 Alleviates Bone Cancer Induced Hyperalgesia Through Inhibition of Pum2

Background

Bone cancer pain (BCP) represents one of the most challenging comorbidities associated with cancer metastasis. Long non-coding RNAs (lncRNAs) have garnered attention as potential therapeutic agents in managing neuropathic pain. However, their role in the regulation of nociceptive information processing remains poorly understood. In this study, we observed a significant down-regulation of the spinal lncRNA ENSRNOG00000051325 (lncRNA51325) in a rat model of bone cancer pain. Our study sought to elucidate the potential involvement of lncRNA51325 in the development of BCP by modulating the expression of molecules associated with pain modulation.

Methods

We established the BCP model by injecting Walker 256 cells into the tibial plateau of rats. We conducted tests on the pain behaviors and anxiety-like responses of rats through von-Frey test, Gait analysis, and Open Field Test. Spinal lumbar expansion was harvested for molecular biology experiments to explore the relationship between lncRNA51325 and Pumilio RNA binding family member 2 (Pum2).

Results

Notably, the overexpression of lncRNA51325 effectively attenuated mechanical allodynia in rats afflicted with BCP, whereas the knockdown of lncRNA51325 induced pain behaviors and anxiety-like responses in naïve rats. Additionally, we observed a time-dependent increase in the expression of Pum2 in BCP-afflicted rats, and intrathecal injection of Pum2-siRNA alleviated hyperalgesia. Furthermore, our investigations revealed that lncRNA51325 exerts a negative modulatory effect on Pum2 expression. The overexpression of lncRNA51325 significantly suppressed Pum2 expression in BCP rats, while the knockdown of lncRNA51325 led to elevated Pum2 protein levels in the spinal cord of naïve rats. Subsequent treatment with Pum2-siRNA mitigated the downregulation of lncRNA51325-induced mechanical allodynia in naïve rats.

Conclusion

Our findings indicate that lncRNA51325 plays a role in regulating bone cancer pain by inhibiting Pum2 expression, offering a promising avenue for novel treatments targeting nociceptive hypersensitivity induced by bone metastatic cancer.

The 2210408F21Rik/miR-1968-5p/Hras axis regulates synapse-related proteins in a mouse model of depressive-like behaviors through a ceRNA mechanism

Abnormal expression of long non-coding RNAs (lncRNAs) has been correlated with depressive disorders, but limited data are available on the lncRNA-microRNA (miRNA/miR)-messenger RNA (mRNA) competitive endogenous RNA (ceRNA) mechanism in depression. Herein, we address this issue based on transcriptome sequencing and in vitro experiments. Mouse hippocampus tissues were obtained from chronic unpredictable mild stress (CUMS)-induced mice to screen out differentially expressed mRNAs and lncRNAs based on the transcriptome sequencing. Next, the depression-related differentially expressed genes (DEGs) were obtained, followed by Gene Ontology (GO) and Kyoto Encylopedia of Genes and Genomes (KEGG) enrichment analysis. A total of 1018 differentially expressed mRNAs, 239 differentially expressed lncRNAs, and 58 DEGs related to depression were acquired. The miRNAs targeting Harvey rat sarcoma virus oncogene (Hras) and miRNAs sponged by Hras-related lncRNA were intersected to identify the ceRNA regulatory network. In addition, the synapse-related genes related to depression were acquired by bioinformatics analysis. Hras was identified as the core gene related to depression, mainly related to neuronal excitation. We also found that 2210408F21Rik competitively bound to miR-1968-5p that targeted Hras. The effects of 2210408F21Rik/miR-1968-5p/Hras axis on neuronal excitation were verified in primary hippocampal neurons. The experimental data indicated that the downregulation of 2210408F21Rik increased the level of miR-1968-5p to diminish Hras expression, thereby affecting neuronal excitation in CUMS mice. In conclusion, the 2210408F21Rik/miR-1968-5p/Hras ceRNA network can potentially affect the expression of synapsia-related proteins and is a promising target for preventing and treating depression.

Identification and validation of Rab11a in Rat orofacial inflammatory pain model induced by CFA

Orofacial pain (OFP) is a clinically very common and the most troubling condition; however, there is few effective way to relieve OFP. Rab11a, a small molecule guanosine triphosphate enzyme, is one of the Rab member family playing a vital role in intracellular endocytosis and the pain process. Therefore, we investigated the hub genes of rat OFP model induced by Complete Freund's Adjuvant (CFA) via re-analyzing microarray data (GSE111160). We found that Rab11a acted as a key hub gene in the process of OFP. During the validation of Rab11a, the OFP model was established by peripheral injection of CFA, which decreased the head withdrawal threshold (HWT) and head withdrawal lantency (HWL). Rab11a was observed in NeuN of Sp5C instead of GFAP/IBA-1, and double-IF of Rab11a and Fos positive cells were increased on the 7th day after CFA modeling statistically. Rab11a protein expression in TG and Sp5C of CFA group was also significantly increased. Interestingly, injection of Rab11a-targeted short hairpin RNA (Rab11a-shRNA) into Sp5C could reverse the decrease in HWT and HWL and reduce the expression level of Rab11a. Electrophysiological recording further demonstrated that the activity of Sp5C neuron was improved in CFA group, while Rab11a-shRNA considerably decreased the enhancement of Sp5C neuronal activity. Finally, we detected the expression level of p-PI3K, p-AKT, and p-mTOR in Sp5C of rats after injecting the Rab11a-shRNA virus. To our surprise, CFA upregulated the phosphorylation of PI3K, AKT and mTOR in Sp5C, and Rab11a-shRNA downregulated these molecules' expression. Our data suggest that CFA activates the PI3K/AKT signaling pathway through up-regulating Rab11a expression, which can induce OFP hyperalgesia development furtherly. Targeting Rab11a may be a novel treatment strategy for OFP.

Neuroinflammation in the medial prefrontal cortex exerts a crucial role in bone cancer pain

Bone cancer pain (BCP) is one of the most common types of pain in cancer patients which compromises the patient's functional status, quality of life, and survival. Central hyperalgesia has increasingly been identified as a crucial factor of BCP, especially in the medial prefrontal cortex (mPFC) which is the main cortical area involved in the process of pain and consequent negative emotion. To explore the genetic changes in the mPFC during BCP occurrence and find possible targets for prediction, we performed transcriptome sequencing of mPFC in the BCP rat model and found a total of 147 differentially expressed mRNAs (DEmRNAs). A protein-protein interaction (PPI) network revealed that the DEmRNAs mainly participate in the inflammatory response. Meanwhile, microglia and astrocytes were activated in the mPFC of BCP rats, further confirming the presence of neuroinflammation. In addition, Gene Ontology (GO) analysis showed that DEmRNAs in the mPFC are mainly involved in antigen processing, presentation of peptide antigen, and immune response, occurring in the MHC protein complex. Besides, the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that DEmRNAs are mainly enriched in the pathways of phagosome, staphylococcus aureus infection, and antigen processing, in which MHCII participate. Furthermore, immunostaining showed that MHCII is mainly located in the microglia. Microglia are believed to be involved in antigen processing, a key cause of BCP. In vivo, minocycline (MC) treatment inhibits the activation of microglia and reduces the expression of MHCII and proinflammatory cytokines, thereby alleviating BCP and pain-related anxiety. Taken together, our study identified differentially expressed genes in the BCP process and demonstrated that the activation of microglia participates in the inflammatory response and antigen process, which may contribute to BCP.