*4.4.4 PKC*

The control of the phosphorylation function of hydroxyl groups of serine and threonine residues in proteins is associated with Protein kinase C (PKC). PKC is also cellular messenger molecule that plays a role in various pathways, including regulation of cell growth and death and response to stresses. This molecule is very sensitive to redox modification, as well [87–89]. On the other hand, some probiotics can affect PKC activity. Corresponding to the previous report (Seth et al., 2008), inhibition of Ro-32-0432 (PKC inhibitor) by soluble proteins p40 and p75 produced by *L. rhamnosus* GG improves H2O2-induced epithelial barrier disorder [85].

#### **4.5 Regulation of the ROS producing enzymes**

Production of ROS through enzymatic reactions and various chemical processes in the host body is essential [90]; because they play an important role in defense

and messaging functions [91]. The human NADPH oxidase (NOX) complex, as the main source of reactive oxygen species [92–94], has seven homologs (NOX1–5, dual oxidase 1 (DUOX1), and DUOX2) [91]. Membrane-bound NOX2 catalytic subunits and p22phox in combination with cytosolic agents (e.g., p40phox, p47phox, p67phox, and small GTPase RAC1, called by neutrophils) cause a respiratory burst (**Figure 4**) [95, 96]. However, oxidative stress occurs if there is an imbalance in the production of ROS or a decrease in the level of oxygen-scavenging proteins, which leads to tissue damage and cell death [93].

Probiotics are able to affect the production of ROS by the NOX complex. Based on researches, the probiotic *Bacillus amyloliquefaciens* SC06 reduces the activity of NOX and expression of p47phox (H2O2-induced IPEC-1) and the probiotics *Lactobacillus fermentum* CECT5716, *Lactobacillus coryniformis* CECT5711 (K8) and *Lactobacillus gasseri* CECT5714 (LC9) reduce NOX activity and decrease the mRNA expression of NOX-1 and NOX-4 enzymes (in hypertensive rats), as a result, they reduce the production level of ROS [7, 97].

On the other hand, ROS can be produced during prostaglandin biosynthesis. For example, cyclo-oxygenase (COX) participates in process of prostaglandin biosynthesis [98]. In some diseases, such as atherosclerosis, COX-2 expression is increased [99]. Therefore, it can be said that the production of vascular prostanoids is caused by overexpression of the COX-2 enzyme [100]. Studies have shown that some probiotics can reduce the expression of COX-2 in the host; for example, the commercial probiotic Lacidofil, when used in mice infected with Helicobacter pylori [101]. Furthermore, it has been established that the expression of COX-2 is reduced by *Lactobacillus acidophilus* in Catla thymus macrophages [102].

Improper functioning of cytochrome P450 (CYP) enzymes is associated with overproduction of ROS and oxidative stress conditions [103]; because they are involved in the metabolism of xenobiotic substances [104]. Some probiotics reduce the expression of these enzymes. Matuskova et al. reported *Lactobacillus casei* is involved in reducing the expression of CYP1A1 enzyme in the intestines of male rats [105].

**Figure 4.** *NADPH oxidase (NOX) complex regulated by probiotics.*

*Functional Foods and Antioxidant Effects: Emphasizing the Role of Probiotics DOI: http://dx.doi.org/10.5772/intechopen.104322*
