Saliva induces disturbance of antimicrobial peptides and promotes intracellular killing of bacteria in keratinocytes by epidermal growth factor receptor transactivation.
Wounds in the mouth, constantly exposed to both saliva and bacteria, heal quickly without infection. Furthermore, during licking of skin wounds, saliva increase wound healing and plays a role in keeping the wound free of infection.
To investigate whether saliva leads to expression of antimicrobial peptides (AMPs) in human epidermal keratinocytes and whether saliva pincrease clearance of intracellular bacteria in these cells.
Expression of AMPs was investigated in the oral mucosa and ex vivo injured skin by immunohistochemistry. Human beta-defensin-3 expression was investigated in epidermal keratinocytes after saliva stimulation, using real-time polymerase chain reaction and immunofluorescence.
We found higher expression of AMPs in the oral mucosa than in the epidermis. Saliva accelerated the injury-induced expression of AMPs in human skin ex vivo and was a potent inducer of the expression of AMPs in epidermal keratinocytes. The expression of AMPs was induced by metalloproteinase-dependent epidermal growth factor receptor (EGFR) transactivation mediated by a salivary lipid. Saliva increased the intracellular clearance of Staphylococcus aureus in keratinocytes through EGFR activation
These findings suggest a previously unreported role of saliva in innate immunity and demonstrate for the first time that saliva induces gene expression in epidermal keratinocytes.
A study published online in The FASEB Journal delves into the mystifying fact that wounds in your mouth heal faster and more efficiently than wounds elsewhere. Until now, it was understood that saliva played a part in the wound healing process, though the extent of its role was unknown. The study examined the effects of salivary peptide histatin-1 on angiogenesis (blood vessel formation), which is critical to the efficiency of wound healing. Researchers found that histatin-1 promotes angiogenesis, as well as cell adhesion and migration.
"These findings open new alternatives to better understand the biology underlying the differences between oral and skin wound healing," said Vicente A. Torres, Ph.D., associate professor at the Institute for Research in Dental Sciences within the Faculty of Dentistry at the University of Chile in Santiago, Chile. "We believe that the study could help the design of better approaches to improve wound healing in tissues other than the mouth."
The study involved experiments at three levels: endothelial, or blood vessel- forming, cells in culture, chicken embryos as animal models, and saliva samples obtained from healthy donors. Using these three models, histatin-1 and saliva were found to increase blood vessel formation. Researchers are now taking the next step in this line of study - using these molecules to generate materials and implants to aid in wound healing.
Cats, dogs, mice and primates. Apart from them all being mammals, each of these groups of animals, us included, tend to lick their wounds. If you’ve ever had a paper cut or something similar, you may have quickly sucked on the finger or thumb that was cut. Many domesticated pets lick their wounds to promote healing, so should we be licking our wounds too?
Well, yes and no. There are health benefits and health hazards associated with humans licking their wounds.
The mucosa (membrane lining) of our mouths heals faster than our skin. This suggests that our saliva may have properties that aid in healing wounds. As it turns out, it does! Enzymes in our saliva, like lysozyme and peroxidase, are antibacterial in their nature. Even antibodies are present in our saliva that can ward off bacteria and viruses. Growth factors, like histatin, can also induce antimicrobial peptides. Licking can also remove any dead, damaged or infected tissue, to improve the healing potential of any remaining healthy tissue. It can also remove any gross contamination of the wound.
But there is a risk of severe consequences that arise from licking one’s wounds. There’s a reason why human bites are regarded as being more dangerous than animal bites. That’s because our saliva also contains a wide range of bacteria that are harmless to us while in the mouth, but can cause further infection to a wound if introduced. The New England Journal of Medicine had a letter published in its April 2002 edition that described how doctors in Germany had to amputate a diabetic man’s thumb after he cut it in a bicycle accident. He licked his wound. The bacteria Eikenella corrodens resides in the mouth and is fine there but, particularly for diabetics, it can have dire consequences.
Wound licking: good or bad?
A 2008 study published by Dutch researchers suggests putting saliva in contact with an open wound comes with many benefits. It seems a certain compound of saliva called histatin not only kills bacteria, preventing infections, but also accelerates healing.
The researchers first collected epithelial cells from the inner cheek then cultured them in multiple petri dishes until the surface was completely covered in cells. An incision was then made in the cell layer by scratching away a small area of the cells.
One dish was bathed in isotonic fluid containing the same number of dissolved particles as blood. But other dishes were bathed in glorious human saliva. Sixteen hours later, the scientists reported the saliva-treated artificial wound was almost completely closed while untreated dishes had a substantial part of the ‘wound’ still open. Then, it was only a matter of singling each saliva component to find out which one was responsible for the accelerated healing property.
Extra :
Swallowing gum: Is it harmful?
Although chewing gum is designed to be chewed and not swallowed, it generally isn't harmful if swallowed. Folklore suggests that swallowed gum sits in your stomach for seven years before it can be digested. But this isn't true. If you swallow gum, it's true that your body can't digest it. But the gum doesn't stay in your stomach. It moves relatively intact through your digestive system and is excreted in your stool.
On rare occasions, large amounts of swallowed gum combined with constipation have blocked intestines in children. It's for this reason that frequent swallowing of chewing gum should be discouraged, especially in children.
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SOURCES :
https://www.ncbi.nlm.nih.gov/pubmed/27453053
https://www.sciencedaily.com/releases/2017/08/170807110331.htm
https://blogs.unimelb.edu.au/sciencecommunication/2013/10/15/do-our-tongues-harm-or-heal/
https://www.zmescience.com/science/licking-wounds-good-or-bad/
https://www.mayoclinic.org/digestive-system/expert-answers/faq-20058446
Source: https://www.ncbi.nlm.nih.gov/m/pubmed/27453053/
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