The effect of ex vivo lipopolysaccharide stimulation and nutrient availability on transition cow innate immune cell AKT/mTOR pathway responsiveness

Molecular Mechanisms Associated with the Development of the Metritis Complex in Dairy Cattle

The metritis complex (MC), a group of post-partum uterine diseases, is associated with increased treatment costs and reduced milk yield and fertility. The goal of this study was to identify genetic variants, genes, or genomic regions that modulate MC disease. A genome-wide association study was performed using a single-locus mixed linear model of 1967 genotypes (624,460 SNPs) and metritis complex records. Then, in-silico functional analyses were performed to detect biological mechanisms and pathways associated with the development of MC. The ATP8A2, COX16, AMN, and TRAF3 genes, located on chromosomes 12, 10, and 21, were associated with MC at p ≤ 0.0001. These genes are involved in the regulation of cholesterol metabolism in the stromal tissue of the uterus, which can be directly associated with the mode of transmission for pathogens causing the metritis complex. The modulation of cholesterol abundance alters the efficiency of virulence factors and may affect the susceptibility of the host to infection. The SIPA1L1, DEPDC5, and RNF122 genes were also significantly associated with MC at p ≤ 0.0001 and are involved in the PI3k-Akt pathway, responsible for activating the autophagic processes. Thus, the dysregulation of these genes allows for unhindered bacterial invasion, replication, and survival within the endometrium.

Inhibition of mTOR in bovine monocyte derived macrophages and dendritic cells provides a potential mechanism for postpartum immune dysfunction in dairy cows

Dairy cattle experience a profound nutrient deficit postpartum that is associated with immune dysfunction characterized by heightened inflammation and reduced pathogen clearance. The activation of the central nutrient-sensing mTOR pathway is comparatively reduced in leukocytes of early postpartum dairy cows during this time of most pronounced nutrient deficit. We assessed the effect of pharmacological mTOR inhibition (Torin-1, rapamycin) on differentiation of monocyte derived classically (M1) and alternatively (M2) activated macrophages (MPh) and dendritic cells (moDC) from 12 adult dairy cows. Treatment with mTOR inhibitors generated M1 MPh with increased oxidative burst and expression of IL12 subunits but decreased phagocytosis and expression of IL1B, IL6, and IL10. In M2 MPh, treatment inhibited expression of regulatory features (CD163, ARG2, IL10) skewing the cells toward an M1-like phenotype. In moDC, mTOR inhibition increased expression of pro-inflammatory cytokines (IL12A, IL12B, IL1B, IL6) and surface CD80. In co-culture with mixed lymphocytes, mTOR-inhibited moDC exhibited a cytokine profile favoring a Th1 response with increased TNF and IFNG production and decreased IL10 concentrations. We conclude that mTOR inhibition in vitro promoted differentiation of inflammatory macrophages with reduced regulatory features and generation of Th1-favoring dendritic cells. These mechanisms could contribute to immune dysregulation in postpartum dairy cows.

Pharmacological inhibition of the mTOR pathway alters phenotype and cytokine expression in bovine monocyte-derived dendritic cells

Epidemiological studies have long demonstrated the association of nutrient status and immune dysfunction in dairy cows. Postpartum dairy cows experiencing a nutrient deficit show a propensity for increased inflammatory response, decreased pathogen clearance, and increased incidence of infectious disease. Studies in cows and other species show that the nutrient sensing mechanistic target of rapamycin (mTOR) signaling pathway could be one potential causal pathway connecting the deficit in nutrient availability and the heightened inflammatory response. Our objective was to investigate the effects of pharmacological mTOR pathway inhibition on phenotype and cytokine expression of bovine monocyte derived dendritic cells (moDC). We differentiated CD14⁺ monocytes from dairy cows (n = 14) into moDC in the presence or absence of first- or second-generation mTOR inhibitor rapamycin and PP242 (both 100 nM), respectively. On day seven cells were matured with E. coli lipopolysaccharide (LPS, 100 ng/mL) or left unstimulated to represent naïve moDC. Surface expression of CD14, CD40, CD80, and MHCII was measured via flow cytometry. We measured mRNA expression of IL10, IL12A, IL12B, and TNFα by rt-qPCR, and protein concentrations of IL-10 and TFN-α in cell culture supernatants with a bead-based multiplex assay. Cultures from ten cows successfully developed the moDC phenotype in culture without inhibitors, defined as increased surface expression of CD40, CD80, and MHCII compared with naïve moDC. Only data from these cows were considered for the results on effects of mTOR inhibitors. In naïve and mature moDC mTOR inhibition increased MHCII expression compared to controls. In mature moDC, in addition to MHCII, CD80 expression was increased compared with untreated LPS-stimulated controls. Expression of IL12A mRNA was upregulated in mature, mTOR inhibited moDC compared with untreated controls. In cell culture supernatants mTOR inhibition reduced IL-10 and increased TNF-α concentrations in naïve and mature moDCs compared with untreated controls. Overall rapamycin had a more consistent effect on altering phenotype and cytokine expression of moDC than PP242. In summary we observed an increased expression of co-stimulatory molecules and antigen presentation potential in mature moDC differentiated under mTOR inhibition, and a cytokine pattern that would potentially favor a Th1 type response. This study provides novel data indicating a role for mTOR signaling in bovine moDC phenotype and mediator profile. This proof-of-concept study demonstrates the role of the mTOR pathway in shaping the bovine immune response and may help to provide mechanistic insight and opportunities for modulation of the immune response during the nutrient deficit of early lactation.

Exosomes in Epilepsy of Tuberous Sclerosis Complex: Carriers of Pro-Inflammatory MicroRNAs

Exosomes are a class of small, secreted extracellular vesicles (EV) that have recently gained considerable attention for their role in normal cellular function, disease processes and potential as biomarkers. Exosomes serve as intercellular messengers and carry molecular cargo that can alter gene expression and the phenotype of recipient cells. Here, we investigated alterations of microRNA cargo in exosomes secreted by epileptogenic tissue in tuberous sclerosis complex (TSC), a multi-system genetic disorder that includes brain lesions known as tubers. Approximately 90% of TSC patients suffer from seizures that originate from tubers, and ~60% are resistant to antiseizure drugs. It is unknown why some tubers cause seizures while others do not, and the molecular basis of drug-resistant epilepsy is not well understood. It is believed that neuroinflammation is involved, and characterization of this mechanism may be key to disrupting the "vicious cycle" between seizures, neuroinflammation, and increased seizure susceptibility. We isolated exosomes from epileptogenic and non-epileptogenic TSC tubers, and we identified differences in their microRNA cargo using small RNA-seq. We identified 12 microRNAs (including miR-142-3p, miR-223-3p and miR-21-5p) that are significantly increased in epileptogenic tubers and contain nucleic acid motifs that activate toll-like receptors (TLR7/8), initiating a neuroinflammatory cascade. Exosomes from epileptogenic tissue caused induction of key pathways in cultured cells, including innate immune signaling (TLR), inflammatory response and key signaling nodes SQSTM1 (p62) and CDKN1A (p21). Genes induced in vitro were also significantly upregulated in epileptogenic tissue. These results provide new evidence on the role of exosomes and non-coding RNA cargo in the neuroinflammatory cascade of epilepsy and may help advance the development of novel biomarkers and therapeutic approaches for the treatment of drug-resistant epilepsy.