Team:UniSalento Lecce/Application2

Probiotics to sequester the nickel excess in the intestine

Nickel is a heavy metal, known today primarily as a pollutant. But naturally, this substance also has a role in biological systems, where it is present in very small quantities: the biological function of nickel is involved in hormonal metabolism, in maintaining the integrity of cell membranes, as a component of certain enzymes (arginase, trypsin, carboxylases), in the metabolism of glucose and lipids and in the stabilization of nucleic acids.

In recent decades, nickel has become famous for the increase in individuals allergic to this chemical element: Italy is the first country in Europe to the prevalence of individuals allergic to nickel, equal to about 32%. How does it manifest this allergy? According to two forms: allergic contact dermatitis (mainly when the metal comes in contact with skin and mucous membranes) and systemic nickel allergy syndrome, SNAS (mainly when the metal enters the human body through food). Food usually contains a few micrograms of nickel, but with the pollution of soils, levels go up to hundreds of micrograms (cereals and legumes are among the nickel richest foods). Since the absorption of nickel takes place for the most part in the intestine, and knowing the efficient homeostasis of nickel in Helicobacter pylori, our team thought it would be useful to engineer some species of bacteria commonly used as probiotics with the protein Hpn, which has the characteristic to bind the nickel with high affinity, removing it from the bowel. The idea is to use gram-negative species harmless to human health, such as Bacillus or Lactobacillus: the former tends to form spores in their life cycle, so they may easily pass the gastric barrier and germinate in the gut, going to compete with the resident flora. Lactobacillus species are normal constituents of the flora present in milk, yogurt and other dairy foods. In particular, just transforming Lactobacilli with Hpn you could create yoghurt or milk suitable for nickel allergic people: they would be not only a safe food but also a real drug. These microorganisms accumulate the metal at cytosolic level through bioconcentration, then they would normally be expelled via the fecal-oral route.