Investigating the ID3/SLC22A4 as immune-related signatures in ischemic stroke

BACKGROUND

Ischemic stroke (IS) is a fearful disease that can cause a variety of immune events. Nevertheless, precise immune-related mechanisms have yet to be systematically elucidated. This study aimed to identify immune-related signatures using machine learning and to validate them with animal experiments and single cell analysis.

METHODS

In this study, we screened 24 differentially expressed genes (DEGs) while identifying immune-related signatures that may play a key role in IS development through a comprehensive strategy between least absolute shrinkage and selection operation (LASSO) regression, support vector machine (SVM) and immune-related genes. In addition, we explored immune infiltration using the CIBERSORT algorithm. Finally, we performed validation in mouse brain tissue and single cell analysis.

RESULTS

We identified 24 DEGs for follow-up analysis. ID3 and SLC22A4 were finally identified as the better immune-related signatures through a comprehensive strategy among DEGs, LASSO, SVM and immune-related genes. RT-qPCR, western blot, and immunofluorescence revealed a significant decrease in ID3 and a significant increase in SLC22A4 in the middle cerebral artery occlusion group. Single cell analysis revealed that ID3 was mainly concentrated in endothelial_2 cells and SLC22A4 in astrocytes in the MCAO group. A CIBERSORT finds significantly altered levels of immune infiltration in IS patients.

CONCLUSIONS

This study focused on immune-related signatures after stroke and ID3 and SLC22A4 may be new therapeutic targets to promote functional recovery after stroke. Furthermore, the association of ID3 and SLC22A4 with immune cells may be a new direction for post-stroke immunotherapy.

Screening genes associated with elevated neutrophil‑to‑lymphocyte ratio in chronic heart failure

Neutrophil‑to‑lymphocyte ratio (NLR) is commonly considered a useful prognostic index for many cardiovascular diseases; however, it has limited sensitivity and specificity. Factors associated with elevated NLR may aid in the prediction of prognosis with heart failure (HF) in combination with NLR. The present study sought to identify decisive factors associated with NLR in HF patients and investigate their association with elevated NLR. The gene expression profile for blood samples from 197 individuals with chronic heart failure (CHF), with corresponding hematological parameters and clinical data were obtained from the public database, GSE77343. Differentially expressed genes (DEGs) were identified, and Gene Ontology and pathway enrichment analyses were performed. The protein‑protein interaction network was constructed with the Search Tool for the Retrieval of Interacting Genes along with Cytoscape. Receiver operating characteristic curves for predictive power, sensitivity and specificity were constructed. The present study identified specific associated DEGs by using Pearson linear correlation and logistic regression analysis. A mean NLR of 3.96 was determined as the cutoff value in the analysis. In total, 31 genes were initially identified as DEGs associated with elevated NLR. They were mainly enriched in neutrophil activation and neutrophil mediated immunity, in fluid shear stress and atherosclerosis, and transcriptional misregulation in cancer. Three focused DEGs, solute carrier family 22 member 4 (SLC22A4), interleukin‑1 receptor 2 (IL1R2) and vanin 3 (VNN3), were finally revealed to be independently associated with elevated NLR in CHF patients. The present study demonstrated that the three genes SLC22A4, IL1R2 and VNN3 may be independently associated with elevated NLR in CHF patients as potential decisive factors of NLR.

Prenatal exposure to brain-specific anion transporter-1-specific monoclonal antibodies impairs cognitive function in post-natal life

Subclinical hypothyroidism is caused by thyroid hormone deficit and can lead to impairments in mood and cognition. In brain, supply with thyroxine (T4) is mediated by thyroid hormone transporters including the brain-specific anion transporter-1 (BSAT-1). In humans and rodents, BSAT-1 is expressed in brain microvessels and astrocytes. In this study, we tested whether exposure in utero with BSAT-1-specific monoclonal antibodies (MabBSAT) will affect the cognitive function of the progeny. On gestation day 16th, females were intravenously treated with MabBSAT, non-specific antibodies (control 1), and saline (control 2). 72h after injection, MabBSAT were still detectable in the rat brain while non-specific antibodies were found. Immunocytochemistry showed that MabBSAT can bind to cultured primary cerebrovascular rat cells. At the age of 1month, the progeny was subjected to the Y-maze test, novel object recognition test, passive avoidance test, and Morris water maze, which revealed significant impairments in the cognitive function in the MabBSAT-exposed progeny compared to both control progeny groups. Therefore, prenatal exposure to MabBSAT blocks brain BSAT-1 and limits T4 influx to the brain. This impairs the cognitive function in exposed progeny in the post-natal life.

Transmission of HIV-1 CTL escape variants provides HLA-mismatched recipients with a survival advantage

One of the most important genetic factors known to affect the rate of disease progression in HIV-infected individuals is the genotype at the Class I Human Leukocyte Antigen (HLA) locus, which determines the HIV peptides targeted by cytotoxic T-lymphocytes (CTLs). Individuals with HLA-B*57 or B*5801 alleles, for example, target functionally important parts of the Gag protein. Mutants that escape these CTL responses may have lower fitness than the wild-type and can be associated with slower disease progression. Transmission of the escape variant to individuals without these HLA alleles is associated with rapid reversion to wild-type. However, the question of whether infection with an escape mutant offers an advantage to newly infected hosts has not been addressed. Here we investigate the relationship between the genotypes of transmitted viruses and prognostic markers of disease progression and show that infection with HLA-B*57/B*5801 escape mutants is associated with lower viral load and higher CD4+ counts.

Following infection with HIV, it is well established that a person's genetic makeup is a major determinant of how quickly they will progress to AIDS. Particularly important is the class I Human leukocyte antigen (HLA) gene that is responsible for alerting the immune system to HIV's presence. One of the reasons our immune systems are unable to beat HIV is that the virus can mutate to forms that our HLA genes no longer recognise. However, some people have versions of the HLA gene (for example HLA-B*57 and HLA-B*5801) that are known to force HIV to tolerate mutations that damage its ability to reproduce. Slower HIV reproduction is thought to be one reason that HLA-B*57 and HLA-B*5801 positive people progress to AIDS more slowly than most other HIV infected persons. We report here on a study of HLA-B*57 and HLA-B*5801 negative women in which better control of disease tended to be associated with their being infected with viruses carrying mutations that have been previously shown to reduce replication. These mutations characterise viruses found infecting HLA-B*57 and HLA-B*5801 positive people. This indicates for the first time that HLA-B*57 or HLA-B*5801 negative people that are infected by such reproductively compromised viruses may also experience better survival prospects.

Membrane localization and pH-dependent transport of a newly cloned organic cation transporter (PMAT) in kidney cells

Plasma membrane monoamine transporter (PMAT) is a novel membrane transporter recently cloned and characterized in our laboratory. We previously demonstrated that PMAT functions as a polyspecific organic cation transporter and efficiently transports many organic cations such as monoamine neurotransmitters and 1-methyl-4-phenylpyridinium (MPP(+)). In this study, we explored the role of PMAT in the renal handling of organic cations. Using a polyclonal antibody generated toward the NH(2)-terminal 66 amino acid residues of human PMAT, we showed that the PMAT protein (approximately 55 kDa) is expressed in the human kidney and is primarily targeted to the apical membranes when expressed in polarized Madin-Darby canine kidney (MDCK) cells. Using MDCK cells stably expressing human PMAT, we showed that PMAT-mediated MPP(+) uptake is strongly dependent on extracellular pH. Lowering extracellular pH from 7.4 to 6.6 greatly stimulated PMAT-mediated MPP(+) uptake, whereas elevating extracellular pH to 8.2 abolished transporter activity. Kinetic analysis revealed that the apparent V(max) at pH 6.6 is about fourfold higher than that at pH 7.4, whereas the apparent K(m) values were not statistically different at these two conditions. Under acidic conditions (pH 6.6), the proton ionophore, carbonyl cyanide p-trifluormethoxyphenylhydrazone, drastically reduced PMAT-mediated MPP(+) uptake, suggesting that the stimulatory effect of proton may be due to transporter coupling with a proton gradient. Taken together, our data suggest that PMAT is expressed on the apical membranes of renal epithelial cells and may use luminal proton gradient to drive organic cation reabsorption in the kidney.

MUC1 cytoplasmic tail detection using CT33 polyclonal and CT2 monoclonal antibodies in breast and colorectal tissue

The immunohistochemical detection (IHC) of MUC1-CT employing a polyclonal antibody (CT33) in relation to CT2 monoclonal antibody (MAb) was analyzed. Western blot (WB) was used to determine the molecular mass of CT.

MATERIALS AND METHODS

We studied 163 breast and 89 colorectal cancer specimens, 10 breast and 14 colorectal benign conditions, and 12 breast and 20 colorectal normal samples. From each tumor sample, subcellular fractions were obtained and analyzed by SDS-PAGE and WB. A nonparametric statistical analysis was employed; data were standardized and a Kendall-Tau correlation was applied.

RESULTS

By IHC, 146/163 (90%) and 151/163 (93%) of breast cancer were positive with CT33 and CT2, respectively; a statistically significant correlation was obtained (t=0.5199). Seven out of ten (70%) benign breast specimens were positive with CT33 while all samples stained with CT2; in normal breast sample tissues, all were positive with both Abs. In colorectal cancer samples, both antibodies stained 47/89 (53%) samples; CT2 reacted in 13/14 (93%) of benign samples while CT33 showed a positive reaction in 9/14 (64%) of benign specimens. In normal samples, CT2 showed staining in 17/20 (85%) of samples and CT33 was reactive in 12/20 (60%). By WB, in breast and colorectal cancer samples, similar results were obtained with both antibodies: a main band at about 30kDa which represents the smaller subunit.

CONCLUSION

CT33 polyclonal antibody has demonstrated its efficacy to detect MUC1 in breast and colorectal cancer tissues with similar reactivity to CT2. It is worthwhile to affirm that CT33 is a good indicator of MUC1 expression.

Epitope shared by functional variant of organic cation/carnitine transporter, OCTN1, Campylobacter jejuni and Mycobacterium paratuberculosis may underlie susceptibility to Crohn’s disease at 5q31

Campylobacter jejuni and Mycobacterium paratuberculosis have been implicated in the pathogenesis of Crohn's disease. The presence of bacterial metabolites in the colonic lumen causing a specific breakdown of fatty acid oxidation in colonic epithelial cells has been suggested as an initiating event in inflammatory bowel disease (IBD). l-Carnitine is a small highly polar zwitterion that plays an essential role in fatty acid oxidation and ATP generation in intestinal bioenergetic metabolism. The organic cation/carnitine transporters, OCTN1 and OCTN2, function primarily in the transport of l-carnitine and elimination of cationic drugs in the intestine. High-resolution linkage disequilibrium mapping has identified a region of about 250kb in size at 5q31 (IBD5) encompassing the OCTN1 and -2 genes, to confer susceptibility to Crohn's disease. Recently, two variants in the OCTN1 and OCTN2 genes have been shown to form a haplotype which is associated with susceptibility to Crohn's. We show that OCTN1 and OCTN2 are strongly expressed in target areas for IBD such as ileum and colon. Further, we have now identified a nine amino acid epitope shared by this functional variant of OCTN1 (Leu503Phe) (which decreases the efficiency of carnitine transport), and by C. jejuni (9 aa) and M. paratuberculosis (6 aa). The prevalence of this variant of OCTN1 (Phe503:Leu503) is 3-fold lower in unaffected individuals of Jewish origin (1:3.44) compared to unaffected individuals of non-Jewish origin (1:1). We hypothesize that a specific antibody raised to this epitope during C. jejuni or M. paratuberculosis enterocolitis would cross-react with the intestinal epithelial cell functional variant of OCTN1, an already less efficient carnitine transporter, leading to an impairment of mitochondrial beta-oxidation which may then serve as an initiating event in IBD. This impairment of l-carnitine transport by OCTN1 may respond to high-dose l-carnitine therapy.

OCTN3 is a mammalian peroxisomal membrane carnitine transporter

Carnitine is a zwitterion essential for the beta-oxidation of fatty acids. The role of the carnitine system is to maintain homeostasis in the acyl-CoA pools of the cell, keeping the acyl-CoA/CoA pool constant even under conditions of very high acyl-CoA turnover, thereby providing cells with a critical source of free CoA. Carnitine derivatives can be moved across intracellular barriers providing a shuttle mechanism between mitochondria, peroxisomes, and microsomes. We now demonstrate expression and colocalization of mOctn3, the intermediate-affinity carnitine transporter (Km 20 microM), and catalase in murine liver peroxisomes by TEM using immunogold labelled anti-mOctn3 and anti-catalase antibodies. We further demonstrate expression of hOCTN3 in control human cultured skin fibroblasts both by Western blotting and immunostaining analysis using our specific anti-mOctn3 antibody. In contrast with two peroxisomal biogenesis disorders, we show reduced expression of hOCTN3 in human PEX 1 deficient Zellweger fibroblasts in which the uptake of peroxisomal matrix enzymes is impaired but the biosynthesis of peroxisomal membrane proteins is normal, versus a complete absence of hOCTN3 in human PEX 19 deficient Zellweger fibroblasts in which both the uptake of peroxisomal matrix enzymes as well as peroxisomal membranes are deficient. This supports the localization of hOCTN3 to the peroxisomal membrane. Given the impermeability of the peroxisomal membrane and the key role of carnitine in the transport of different chain-shortened products out of peroxisomes, there appears to be a critical need for the intermediate-affinity carnitine/organic cation transporter, OCTN3, on peroxisomal membranes now shown to be expressed in both human and murine peroxisomes. This Octn3 localization is in keeping with the essential role of carnitine in peroxisomal lipid metabolism.