IDO1 and IDO2 gene expression analysis by quantitative polymerase chain reaction

Differential expression of biomarkers in saliva related to SARS-CoV-2 infection in patients with mild, moderate and severe COVID-19

BACKGROUND

Severe COVID-19 is a disease characterized by profound dysregulation of the innate immune system. There is a need to identify highly reliable prognostic biomarkers that can be rapidly assessed in body fluids for early identification of patients at higher risk for hospitalization and/or death. This study aimed to assess whether differential gene expression of immune response molecules and cellular enzymes, detected in saliva samples of COVID-19 patients, occurs according to disease severity staging.

METHODS

In this cross-sectional study, subjects with a COVID-19 diagnosis were classified as having mild, moderate, or severe disease based on clinical features. Transcripts of genes encoding 6 biomarkers, IL-1β, IL-6, IL-10, C-reactive protein, IDO1 and ACE2, were measured by RT‒qPCR in saliva samples of patients and COVID-19-free individuals.

RESULTS

The gene expression levels of all 6 biomarkers in saliva were significantly increased in severe disease patients compared to mild/moderate disease patients and healthy controls. A significant strong inverse relationship between oxemia and the level of expression of the 6 biomarkers (Spearman's correlation coefficient between -0.692 and -0.757; p < 0.001) was found.

CONCLUSIONS

Biomarker gene expression determined in saliva samples still needs to be validated as a potentially valuable predictor of severe clinical outcomes early at the onset of COVID-19 symptoms.

An Ancient Mutation in the TPH1 Gene is Consistent with the Changes in Mammalian Reproductive Rhythm

The reproductive rhythm undergoes several changes during the evolution of mammals to adapt to local environmental changes. Although the critical roles of melatonin (MLT) in the formation of reproductive rhythm have been well established, the genetic basis for the changes of reproductive rhythm remains uncertain. Here, we constructed the phylogenetic trees of 13 melatonin synthesis, metabolism and receptor genes, estimated their divergence times, and calculated their selection pressures. Then, we evaluated the effect of positively selected and functionally related mutations on protein activity. Our results showed that there were significant positive selection sites in the three major genes, including tryptophan hydroxylase 1 (TPH1), tryptophan hydroxylase 2 (TPH2) and indoleamine-2,3-dioxygenase 1 (IDO1) that are involved in melatonin synthesis, metabolism and function. At the protein level, amino acids at the 442nd site of TPH1 protein and the 194th, 286th, 315th and 404th sites of IDO1 protein were under positive selection, and the variants of the amino acid in these sites might lead to the changes in protein function. Remarkably, the 442nd site of these positive selection sites is in the tetramerization domain of TPH1 protein, and it is proline or leucine. At this site, 89.5% of the amino acid of non-seasonal reproducing mammals was proline, while that of 88.9% of seasonal reproducing mammals was leucine. This variation of the amino acid was derived from the T/C polymorphism at the 1325th site of the TPH1 gene coding sequence, which significantly altered the TPH1 activity (p < 0.01). Interestingly, the predicted age of the allele C in the mammalian genome appeared about 126.6 million years ago, and allele T appeared about 212.6 million years ago, indicating that the evolution of the TPH1 gene was affected by the two mammalian split events and the K-T extinction event. In conclusion, the T/C polymorphism at the 1325th site in the TPH1 gene coding sequence altered TPH1 activity, suggesting that this polymorphism is consistent with the reproductive rhythm of mammals.

Influence of Xiaoyaosan on depressive-like behaviors in chronic stress-depressed rats through regulating tryptophan metabolism in hippocampus

BACKGROUND

Tryptophan metabolism has always been considered to play a vital role in mental disorder diseases, and how traditional Chinese formula Xiaoyaosan regulates the tryptophan metabolism is a complement to the pathogenesis of depression. This study established a depression rat model by the chronic immobilization stress (CIS) method and observed the change in tryptophan metabolism in hippocampus and the effects of Xiaoyaosan.

METHODS

Forty-eight male Sprague Dawley (SD) rats were randomly divided into the following four groups: control group, CIS group, Xiaoyaosan group, and fluoxetine group. The depression model was established by the 21-day CIS. The food intake and body weight were recorded, and the sucrose preference test (SPT), novelty suppressed feeding (NSF) test and open field test (OFT) were also used to evaluate the model. Then, the contents of tryptophan and 5-hydroxytryptamine (5-HT) in hippocampus were detected by the ELISA method, and the expression levels of tryptophan hydrogenase 2 (TPH2) and indoleamine 2,3-dioxygenase 1 (IDO1) in hippocampus were determined by quantitative reverse transcriptase polymerase chain reaction reaction (qRT-PCR) and Western blot methods.

RESULTS

The behavioral data showed a significant difference between the model group and the normal group. The 5-HT content in the hippocampi of CIS rats was significantly reduced, whereas the tryptophan content in the hippocampi of model rats was significantly increased. The TPH2 level in hippocampus of the model group was significantly decreased, and the IDO1 level was significantly increased. Xiaoyaosan and fluoxetine could significantly reverse these changes and had obvious curative effects.

CONCLUSION

The abnormal tryptophan metabolism existed in the hippocampi of chronic stress-depressed rats, which was closely related to the pathogenesis of depression. Xiaoyaosan could improve the tryptophan metabolism by regulating the expression levels of TPH2 and IDO1, thus exerting an antidepressant-like effect.

Interferon Lambda Upregulates IDO1 Expression in Respiratory Epithelial Cells After Influenza Virus Infection

Influenza infection causes an increase in indoleamine 2, 3-dioxygenase (IDO) activity in the lung parenchyma. IDO catabolizes tryptophan into kynurenine, leading to immune dampening. Multiple cell types express IDO, and while IFN-γ upregulates IDO in dendritic cells and macrophages, it is unclear how IDO is affected in respiratory epithelial cells during influenza infection. In this study, the role of IFN-λ in IDO regulation was investigated after influenza infection of respiratory epithelial cells. IDO1 expression increased concurrently with IFN-λ expression. In differentiated NHBE cells, the IDO metabolite was released basolaterally. Recombinant IFN-λ upregulated IDO1 activity, and silencing of IFN-λ decreased IDO1 expression during influenza infection. During IFN-λ stimulation, most differentiated cell types are able to express IDO but during influenza infection, IDO is primarily expressed in uninfected cells. These studies show a role for IDO in the host response to influenza infection, and they provide insights into novel approaches for enhancing vaccine responses and therapeutic approaches.