Overexpression of ASMT likely enhances the resistance of transgenic sheep to brucellosis by influencing immune‐related signaling pathways and gut microbiota

Abstract

Melatonin is a pleiotropic molecule with a variety of biological functions, which include its immunoregulatory action in mammals. Brucellosis is a worldwide endemic zoonotic disease caused by the Brucella, which not only causes huge economic losses for the livestock industry but also impacts human health. To target this problem, in current study, two marker‐free transgenic sheep overexpressing melatonin synthetic enzyme ASMT (acetylserotonin O‐methyltransferase) gene were generated and these melatonin enrich transgenic sheep were challenged by Brucella infection. The results showed that the serum melatonin concentration was significantly higher in transgenic sheep than that of wild type (726.92 ± 70.6074 vs 263.10 ± 34.60 pg/mL, P < .05). Brucella challenge test showed that two thirds (4/6) of the wild‐type sheep had brucellosis, while none of the transgenic sheep were infected. Whole‐blood RNA‐seq results showed that differential expression genes (DEGs) were significantly enriched in natural killer cell‐mediated cytotoxicity, phagosome, antigen processing, and presentation signaling pathways in overexpression sheep. The DEGs of toll‐like receptors (TLRs) and NOD‐like receptors (NLRs) families were verified by qPCR and it showed that TLR1, TLR2, TLR7, CD14, NAIP, and CXCL8 expression levels in overexpression sheep were significantly higher and NLRP1, NLRP3, and TNF expression levels were significantly lower than those of wild type. The rectal feces were subjected to 16S rDNA amplicon sequencing, and the microbial functional analysis showed that the transgenic sheep had significantly lower abundance of microbial genes related to infectious diseases compared to the wild type, indicating overexpression animals are likely more resistant to infectious diseases than wild type. Furthermore, exogenous melatonin treatment relieved brucellosis inflammation by upregulating anti‐inflammatory cytokines IL‐4 and downregulating pro‐inflammatory IL‐2, IL‐6, and IFN‐γ. Our preliminary results provide an informative reference for the study of the relationship between melatonin and brucellosis.

Melatonin: highlighting its use as a potential treatment for SARS-CoV-2 infection

“…Importantly, melatonin prevented the death of premature newborn humans suffering from severe bacterial sepsis or septic shock [ 41 ] and melatonin has been suggested for use in individuals suffering from other serious bacterial infections, including necrotizing fasciitis [ 42 , 43 ]. Recently, elevated levels of endogenous melatonin were found to correlate with the ability to resist brucellosis infection [ 44 ]. As observed by Snider et al [ 45 ] in COVID-19-infected patients, excessive blood levels of sPLA2-IIA (a toxic phospholipase; see below) due to a bacterial infection are consequential in causing lung surfactant changes culminating in acute lung injury [ 46 ].…”

“…Major contributors to the switch from mitochondrial glucose oxidation to the upregulation of pyruvate metabolism in the cytosol often are accompanied by stimulation of hypoxia-inducible factor-1α (HIF-1α) and activation of NF-ҝB and other transcription factors which exaggerate inflammation [53][54][55]. In COVID-19-infected patients, macrophages convert from M2 antiinflammatory to M1 pro-inflammatory cells which, along with other immune cells that exhibit a similar switch, contribute to the cytokine storm which leads to serious damage not only to the respiratory system but also in many other organs, thereby precipitating multiple organ failure [44,56] (Fig. 1).…”

Intestinal microbiota and melatonin in the treatment of secondary injury and complications after spinal cord injury

“… Ghareghani et al (2018) and Xiong et al (2022) demonstrated that melatonin modulates intestinal immune function through the expression of nod-like receptor-related genes and TLRs. By differential expression gene (DEG) and gene ontology (GO) analysis, Tlr1 , Tlr2 , Tlr7 , Cd14 , Naip , Cxcl8 and Nlrp1 , Nlrp3 gene expression levels were found to be significantly increased in ASMT (a key enzyme in the acetyl serine synthesis melatonin pathway) overexpressing transgenic sheep ( Li et al, 2021 ). It is suggested that melanin plays an important role by regulating anti-inflammatory related factors and signaling pathways.…”

The Reserve/Maximum Capacity of Melatonin’s Synthetic Function for the Potential Dimorphism of Melatonin Production and Its Biological Significance in Mammals

“…SNAT or ASMT overexpression in sheep improves their reserve/maximum capacity of synthetic melatonin function compared to WT. As a result, these transgenic sheep exhibit a high tolerance to LPS challenge and also display enhanced resistance to the infectious disease, brucellosis, compared to WT [ 104 , 105 ]. Considering the higher reserve capacity for melatonin synthesis in women compared to in men, women seem to possess a significant advantage over men in tolerating stressful conditions, such as those of infectious diseases [ 106 ].…”