[Music] good morning to everybody I would like to talk about the role of tie junctions sorry the role of tight junctions on the intestinal integrity my presentation we will will be a short presentation because we will have time to discuss deeper during the coffee break if you want so as you know the intestine has took it to critical functions that ensure the intestinal health first one of the main functions of the intestine is to allow the passage the transport of nutrients electrolytes water from the lumen into the circulation but also the intestine has to restrict the passage of pathogens and ditions and also the harmful harmful substrates so the maintenance of these two critical functions are named the intestinal barrier function in poultry production some ingredients and additives improve the intestinal health and determine this improvement not only in terms of production but also in terms of quality of the products obtained consumers safety and animal welfare so one of the components of the intestinal barrier is the selectivity of the epithelium other components that also contribute to this intestinal barrier are microbiota the mucous barrier and the immune system it's important to to notice that these components work all together and they have a really tight relationship with between them let's talk now about in epithelium permeability to cross the epithelium we have two different pathways the transcellular pathway that is associated with that transport across the epithelial cell first through the apical membrane and then through the basolateral membrane we have also another pathway the para cellular pathway that is associated with the transport of the different substrates between the cells by the intercellular space the tight junctions the most apical junctional complex in the epithelia are responsible of the regulation of para cellular permeability dye junctions are formed by different proteins we have in the tie junction the transmembrane proteins distension brain proteins join one cell to the neighbor one and the most studied transmembrane proteins are occluding and also the clothing family in the tie junction we also have cytoplasmic proteins the most studied are the zio family that are the nexus between that these transmembrane proteins with the other component of the 10 Junction that is the cytoskeleton proteins also in the tide junction there are a lot of regulatory proteins that ensure the function the correct function of the digestion but I have a question for the audience which are the functions of tide junction which of these answers do you think that is the correct one ABCD si si the correct one is the t1 because tie junctions not only have not only regulate para cylinder permeability but also tie junctions are able to regulate cellular polarization because tie Junction are in the interface between the apical domain and there was a lateral domain so this tension restrict the movement of proteins from the apical domain to the basolateral domain with the objective to allow a pictorial transport moreover by junctions regulate proliferation and differentiation that is two functions that are very important in epithelial cells let's talk about personal permeability tie junctions determine two pathways the poor pathway that is described it to be a high capacity and a selective pathway this poor pathway allows the passage of mainly ions small and small molecule molecules and is regulated mainly by clothings we have another pathway is the leak pathway this pathway is described it to be a low capacity in a non selective pathway that allows the passage of larger molecules and is regulated by occluding do one underseater skeleton proteins these two pathways are not independent because it is this private that accrued II can also regulate the poor pathway in the middle cultures it is easy to determine for a cellular permeability by measuring the translational electrical resistance that inform us about the resistance of the epithelium to iron fluxes moreover we can measure para cellular permeability by determining the para cellular fluxes of some markers specific from the para cellular pathway like mannitol or some dextrans or the Lucifer yellow in an I have also a question for you in a optimal in an optimal epithelial barrier function the transitional electrical resistance values are high or low what do you think hi okay correct the epithelium resistance to ion fluxes is very high in a normal situation but when this barrier is disrupted these these values these tier values decrease in contrast a cellular fluxes of these markers of the para cellular pathway what do you think in optimal situation these fluxes are higher low low perfect an optimal barrier is characterized by low fluxes of these para cellular markers but when there is a disruption of this barrier these fluxes are increased tear is not able to difference to discriminate between the poor and the lik pathway and to discriminate with with these two pathways we have to use some larger Paris annular markers with a high molecular weight to in order to differentiate between the poor and alec pathway so a little Russian of tie Junction instructor leads to an increase in Paris annular permeability this increase in Paris annular permeability could be by different mechanism one of the mechanism involved in the disruption of the Junction structure is a decrease in the expression the genetic and also the protein expression of some tie Junction protein in this sense some tight junctions protein could regulate the gene expression but also a disruption of digestion structure could be due to the localization of digestion proteins from the plasma membrane to the citizen moreover another way to disrupt the detention instructor is to produce a contraction of the actor mucin ring in that case with a contraction of this these proteins we obtain an opening of the Opera cellular pathway so tight junctions can be regulated in response to both physiological and pathological stimuli let's see some examples one of the well-defined example of physiological regulation of tie junction is that following the activation of nutrient coal transport the transport of glucose and some amino acids with sodium leads to activate the Machine light-chain kinase this enzyme is able to produce a contraction of the actor machinery and also I produce a slight dye Junction internalisation so in that case there is a slight increase in titanium variability which which is the objective of that the objective is to increase water absorption and to increase also the para cellular transport of small nutrients but mainly that the Junction's could be regulated in pathological situations and one of the actors that that that are involved in these pathological regulations are cytokines another and also oxidative stress one of the main cytokines that has is involved in the regulation of ty Junction is TNF alpha this pro-inflammatory cytokine is able to induce also but in that case more of a more pronounced in activation of this myosin light-chain kinase in that case this activation leads to a contraction of the activation ring and also leads to an increase of the contraction of the octo machine ring and also pronounce it internalization of occluding from the tight Junction to the cytoplasm it has been described that also oxidative a stress that could be produced by different mechanism could modify the ty Junction structure but it's important to to notice that digestion can be regulated by components of the diet for example a chip DBA the Hydrox analog of methionine is able to partial protect from the disruption of the barrier from the decrease of tear values produced by the tnf-alpha in that case the main results we have obtained is that HM TVA is able to maintain the integrity of occlusion in the tie Junction moreover hm TVA is also described to partially protect from the eruption caused it by erosion peroxide and in that case by maintaining the structure of zero one so it's an example of some the Ituri components that could also regulate the junctions manova probiotics and also the sprite to enhance barrier function to prevent intestinal bowel dysfunction and mainly they do this dysfunction by immune modulation we have observed that also probiotics such as beta lactam Annan's are able to help to the microbiota and to the probiotics to change the balance of the different cytokines with the objective to register ate the epithelial barrier function after salmonella and colonization so to take home it's important to be to be sure that I Junction determine para cellular permeability these tight junctions can be regulated in response not only to physiological but also to pathological stimuli and the last important thing is that tight junctions can be regulated by the Ituri components so thank you very much [Applause] the questions the first question how important is the para cellular absorption compared to transannular depending on the different nutrients the the personal permeability is in optimal situation very low so normally nutrients has to cross the epithelium by the trans teller pathway but in some times normally when the nutrients are very high in the lumen the epithelia could regulate the junction to increase the absorption of this nutrients by the para cellular pathway and tight junctions can regulate the effect of fasting sorry tension can regulate the effect of fasting on that permeability permeability I think yes tight Junction could be regulated depending on the concentration of the different nutrients in the lumen so we we have to keep in mind that the dysregulation is not only to to protect the barrier but also to increase nutrient absorption okay thank you very much [Music]