Melatonin shapes bacterial clearance function of porcine macrophages during enterotoxigenic Escherichia coli infection

Due to the immature gastrointestinal immune system,weaning piglets are highly susceptible to pathogens,e.g.,enterotoxigenic Escherichia coli(ETEC).Generally,pathogens activate the immune cells(e.g.,macrophages)and shape intracellular metabolism(including amino acid metabolism);nevertheless,the metabolic cues of tryptophan(especially melatonin pathway)in directing porcine macrophage function during ETEC infection remain unclear.Therefore,this study aimed to investigate the changes in the serotonin pathway of porcine macrophages during ETEC infection and the effect of melatonin on porcine macrophage functions.Porcine macrophages(3D4/21 cells)were infected with ETEC,and the change of serotonin pathway was analysed by reverse transcription PCR and metabolomic analysis.The effect of melatonin on porcine macrophage function was also studied with proteomic analysis.In order to investigate the effect of melatonin on bacterial clearance function of porcine macrophages during ETEC infection,methods such as bacterial counting,reverse transcription PCR and western blotting were used to detect the corresponding indicators.The results showed that ETEC infection blocked melatonin production in porcine macrophages(P<0.05)which is largely associated with the heat-stable enterotoxin b(STb)of ETEC(P<0.05).Interestingly,melatonin altered porcine macrophage functions,including bacteriostatic and bactericidal activities based on proteomic analysis.In addition,melatonin pretreatment significantly reduced extracellular lactate dehydrogenase(LDH)activity(P<0.05),indicating that melatonin also attenuated ETEC-triggered macrophage death.Moreover,melatonin pretreatment resulted in the decrease of viable ETEC in 3D4/21 cells(P<0.05),suggesting that melatonin enhances bacterial clearance of porcine macrophages.These results suggest that melatonin is particularly important in shaping porcine macrophage function during ETEC infection.

Genetic structure and domestication footprints of the tusk,coat color,and ear morphology in East Chinese pigs

The domestication and artificial selection of wild boars have led to dramatic morphological and behavioral changes,especially in East Chinese(ECN)pigs.Here,we provide insights into the population structure and current genetic diversity of representative ECN pig breeds.We identify a 500-kb region containing six tooth development-relevant genes with almost completely different haplotypes between ECN pigs and Chinese wild boars or European domestic pigs.Notably,the c.195A>G missense mutation in exon 2 of AMBN may cause alterations in its protein structure associated with tusk degradation in ECN pigs.In addition,ESR1 may play an important role in the reproductive performance of ECN pigs.A major haplotype of the large lop ear-related MSRB3 gene and eight alleles in the deafness-related GRM7 gene may affect ear morphology and hearing in ECN pigs.Interestingly,we find that the two-end black(TEB)coat color in Jinhua pigs is most likely caused by EDNRB with genetic mechanisms different from other Chinese TEB pigs.This study identifies key loci that may be artificially selected in Chinese native pigs related to the tusk,coat color,and ear morphology,thus providing new insights into the genetic mechanisms of domesticated pigs.