Is Galanin a Promising Therapeutic Resource for Neural and Nonneural Diseases?

Increased galanin-galanin receptor 1 signaling, inflammation, and insulin resistance are associated with affective symptoms and chronic fatigue syndrome due to long COVID

BACKGROUND

Patients with Long COVID (LC) often experience neuropsychiatric symptoms such as depression, anxiety, and chronic fatigue syndrome (CFS), collectively referred to as the physio-affective phenome of LC. Activated immune-inflammatory pathways and insulin resistance significantly contribute to the physio-affective phenome associated with LC.

METHODS

In a cohort of 90 individuals, categorized into those with and without LC, we evaluated, 3-6 months following acute SARS-CoV-2 infection, the correlations between the Hamilton Depression (HAMD), Hamilton Anxiety (HAMA), and Fibro-Fatigue (FF) Rating Scale scores, and serum C-reactive protein (CRP), prostaglandin E2 (PGE2), galanin-galanin receptor 1 (GAL-GALR1) signaling, insulin resistance, insulin-like growth factor (IGF-1), plasminogen activator inhibitor-1 (PAI1), S100B and neuron-specific enolase (NSE).

RESULTS

HAMD, HAMA, FF scores, CRP, PGE2, GAL-GALR1 signaling, insulin resistance, PAI1, NSE, and S100B are all higher in people with LC compared to those without LC. The HAMD/HAMA/FF scores were significantly correlated with PGE, CRP, GAL, GALR1, insulin resistance, and PAI1 levels, and a composite score based on peak body temperature (PBT) - oxygen saturation (SpO2) (PBT/SpO2 index) during the acute infectious phase. A combination of biomarkers explained a large part of the variance in CFS and affective scores (33.6%-42.0%), with GAL-GALR1 signaling, PGE2, and CRP being the top 3 most important biomarkers. The inclusion of the PBT/SpO2 index increased the prediction (55.3%-67.1%). The PBT/SpO2 index predicted the increases in GAL-GALR1 signaling.

CONCLUSION

These results indicate that the CFS and affective symptoms that are linked to LC are the consequence of metabolic aberrations, activated immune-inflammatory pathways, and the severity of inflammation during the acute phase of SARS-CoV-2 infection.

Locus coeruleus injury modulates ventral midbrain neuroinflammation during DSS-induced colitis

Parkinson's disease (PD) is characterized by a decades-long prodrome, consisting of a collection of non-motor symptoms that emerges prior to the motor manifestation of the disease. Of these non-motor symptoms, gastrointestinal dysfunction and deficits attributed to central norepinephrine (NE) loss, including mood changes and sleep disturbances, are frequent in the PD population and emerge early in the disease. Evidence is mounting that injury and inflammation in the gut and locus coeruleus (LC), respectively, underlie these symptoms, and the injury of these systems is central to the progression of PD. In this study, we generate a novel two-hit mouse model that captures both features, using dextran sulfate sodium (DSS) to induce gut inflammation and N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) to lesion the LC. We first confirmed the specificity of DSP-4 for central NE using neurochemical methods and fluorescence light-sheet microscopy of cleared tissue, and established that DSS-induced outcomes in the periphery, including weight loss, gross indices of gut injury and systemic inflammation, the loss of tight junction proteins in the colonic epithelium, and markers of colonic inflammation, were unaffected with DSP-4 pre-administration. We then measured alterations in neuroimmune gene expression in the ventral midbrain in response to DSS treatment alone as well as the extent to which prior LC injury modified this response. In this two-hit model we observed that DSS-induced colitis activates the expression of key cytokines and chemokines in the ventral midbrain only in the presence of LC injury and the typical DSS-associated neuroimmune is blunted by pre-LC lesioning with DSP-4. In all, this study supports the growing appreciation for the LC as neuroprotective against inflammation-induced brain injury and draws attention to the potential for NEergic interventions to exert disease-modifying effects under conditions where peripheral inflammation may compromise ventral midbrain dopaminergic neurons and increase the risk for development of PD.

Locus coeruleus injury modulates ventral midbrain neuroinflammation during DSS-induced colitis

Parkinson's disease (PD) is characterized by a decades-long prodrome, consisting of a collection of non-motor symptoms that emerges prior to the motor manifestation of the disease. Of these non-motor symptoms, gastrointestinal dysfunction and deficits attributed to central norepinephrine (NE) loss, including mood changes and sleep disturbances, are frequent in the PD population and emerge early in the disease. Evidence is mounting that injury and inflammation in the gut and locus coeruleus (LC), respectively, underlie these symptoms, and the injury of these systems is central to the progression of PD. In this study, we generate a novel two-hit mouse model that captures both features, using dextran sulfate sodium (DSS) to induce gut inflammation and N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) to lesion the LC. We first confirmed the specificity of DSP-4 for central NE using neurochemical methods and fluorescence light-sheet microscopy of cleared tissue, and established that DSS-induced outcomes in the periphery, including weight loss, gross indices of gut injury and systemic inflammation, the loss of tight junction proteins in the colonic epithelium, and markers of colonic inflammation, were unaffected with DSP-4 pre-administration. We then measured alterations in neuroimmune gene expression in the ventral midbrain in response to DSS treatment alone as well as the extent to which prior LC injury modified this response. In this two-hit model we observed that DSS-induced colitis activates the expression of key cytokines and chemokines in the ventral midbrain only in the presence of LC injury and the typical DSS-associated neuroimmune is blunted by pre-LC lesioning with DSP-4. In all, this study supports the growing appreciation for the LC as neuroprotective against inflammation-induced brain injury and draws attention to the potential for NEergic interventions to exert disease-modifying effects under conditions where peripheral inflammation may compromise ventral midbrain dopaminergic neurons and increase the risk for development of PD.

The GAL/GALR2 axis promotes the perineural invasion of salivary adenoid cystic carcinoma via epithelial-to-mesenchymal transition

BACKGROUND

Perineural invasion (PNI) is a typical pathological characteristic of salivary adenoid cystic carcinoma (SACC) and other neurotrophic cancers. The mechanism of the neural microenvironment controlling tumor progression during the PNI process is unclear. In the present study, we investigated the role and molecular mechanisms of nerve-derived neuropeptide galanin (GAL) and its receptor (GALR2) in the regulation of PNI in SACC.

METHODS

Immunohistochemistry staining and clinical association studies were performed to analyze the expression of GAL and GALR2 in SACC tissues and their clinical value. Dorsal root ganglion or SH-SY5Y cells were co-cultured with SACC cells in vitro to simulate the interactions between the neural microenvironment and tumor cells, and a series of assays including transcriptome sequencing, Western blot, and Transwell were performed to investigate the role and molecular mechanism of GAL and GALR2 in the regulation of SACC cells. Moreover, both the in vitro and in vivo PNI models were established to assess the potential PNI-specific therapeutic effects by blocking the GAL/GALR2 axis.

RESULTS

GAL and GALR2 were highly expressed in SACC tissues, and were associated with PNI and poor prognosis in SACC patients (p < 0.05). Nerve-derived GAL activated GALR2 expression in SACC cells and induced epithelial-to-mesenchymal transition (EMT) in SACC cells. Adding human recombinant GAL to the co-culture system promoted the proliferation, migration, and invasion of SACC cells significantly, but inhibited the apoptosis of SACC cells. Adding M871, a specific antagonist of GALR2, significantly blocked the above effects (p < 0.05) and inhibited the PNI of SACC cells in vitro and in vivo (p < 0.05).

CONCLUSIONS

This study demonstrated that nerve-derived GAL activated GALR2 expression, and promoted EMT in SACC cells, thereby enhancing the PNI process. Interruption of the GAL/GALR2 axis might be a novel strategy for anti-PNI therapy for SACC.

Integrative analysis of potential biomarkers and immune cell infiltration in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disease in the elderly population. However, there are no reliable diagnostic biomarkers for PD, and the pathogenesis of PD still needs further study. The aim of the current study was to identify potential biomarkers and explore the pathogenesis of PD.

METHODS

We conducted an integrative analysis of messenger RNA (mRNA), microRNA (miRNA), and long noncoding RNA (lncRNA) expression profiles of PD using data from the Gene Expression Omnibus (GEO). The GSE110720, GSE110719 and GSE133347 data sets were selected and analysed. Gene ontology (GO) enrichment and gene set variation analysis (GSVA) were performed for annotation, visualization, and integrated discovery. Protein-protein interaction (PPI) and competing endogenous RNA (ceRNA) networks were constructed, and hub genes were identified. Meanwhile, the immune infiltration analysis of hub genes was analysed. Moreover, receiver operating characteristic (ROC) curves were generated to verify the diagnostic value of the differentially expressed genes (DEGs). Finally, the genes with high area under the curve (AUC) values were verified by human samples.

RESULTS

We identified 464 DEGs closely related to PD, including 154 mRNAs, 134 miRNAs, and 176 lncRNAs. The GO analyses indicated that changes in PD were mainly enriched in receptor ligand activity and cytokine receptor binding. The KEGG enrichment analysis showed that these DEGs were significantly involved in cytokine-cytokine receptor interactions, signalling pathways regulating the pluripotency of stem cells and Th17 cell differentiation. GSVA suggested that growth factor binding, IL2-stat5 signalling, and IL6-jak-stat3 signalling were crucial in the development of PD. A total of five hub genes (NPBWR2, CXCL10, CXCL5, S1PR5, and GALR1) were selected via the PPI network. A ceRNA network of the CXCL5, CXCL10 and S1PR5 genes was constructed, and target genes of the three genes were screened. The immune infiltration analysis showed that there were significant differences in a variety of immune cells between the hub genes. The expression of DEGs was validated in clinical human samples by quantitative reverse transcription polymerase chain reaction (qRT-PCR). The expression levels of hsa-miR6895-5p, hsa-miR6791-5p, hsa-miR518f-5p, hsa-miR455-3p and TEKT4P2 were decreased, while the levels of TPTE2P6 were increased in human samples. These findings are consistent with the bioinformatics analysis results.

CONCLUSION

We found that the immune inflammatory response and immune cell regulation were involved in the pathogenesis of PD. Five hub genes involved in the immune infiltration biological processes of PD based on bioinformatics. We verified the DEGs with significant differences by qRT-PCR. These findings might provide new insight into the pathogenesis of PD and the development of diagnostic and therapeutic strategies for PD.

Regulatory Influence of Galanin and GALR1/GALR2 Receptors on Inflamed Uterus Contractility in Pigs

Uterine inflammation is a very common and serious pathology in domestic animals, the development and progression of which often result from disturbed myometrial contractility. We investigated the effect of inflammation on the protein expression of galanin (GAL) receptor subtypes (GALR)1 and GALR2 in myometrium and their role in the contractile amplitude and frequency of an inflamed gilt uterus. The gilts of the E. coli and SAL groups received E. coli suspension or saline in their uteri, respectively, and only laparotomy was performed (CON group). Eight days later, the E. coli group developed severe acute endometritis and lowered GALR1 protein expression in the myometrium. Compared to the pretreatment period, GAL (10⁻⁷ M) reduced the amplitude and frequency in myometrium and endometrium/myometrium of the CON and SAL groups, the amplitude in both stripes and frequency in endometrium/myometrium of the E. coli group. In this group, myometrial frequency after using GAL increased, and it was higher than in other groups. GALR2 antagonist diminished the decrease in amplitude in myometrium and the frequency in endometrium/myometrium (SAL, E. coli groups) induced by GAL (10⁻⁷ M). GALR1/GALR2 antagonist and GAL (10⁻⁷ M) reversed the decrease in amplitude and diminished the decrease in frequency in both examined stripes (CON, SAL groups), and diminished the drop in amplitude and abolished the rise in the frequency in the myometrium (E. coli group). In summary, the inflammation reduced GALR1 protein expression in pig myometrium, and GALR1 and GALR2 participated in the contractile regulation of an inflamed uterus.