**6. Macrophage and T-cell differentiation**

In pathogen infection, dendritic cells (DCs) and macrophages primarily act as phagocytotic antigen-presenting cells (APCs) that degrade infected pathogens into fragments, and then move those fragments to the nearby lymphoid organs. The pathogen fragments combine with cell surface histocompatibility complex (major histocompatibility complex) to activate and differentiate T cells. **Figure 3** displays the cooperation of the antigen-presenting cells, costimulatory molecules and cytokines.

The metabolic organs, such as the liver, pancreas and adipose tissue, are composed of parenchymal and stromal cells, which include macrophages to maintain metabolic homeostasis. Bacterial infection innately activates macrophages, causing the secretion of proinflammatory cytokines, such as TNF-α, IL-6 and IL-1β. This promotes peripheral insulin resistance and reduces nutrient storage during the metabolic reaction. Furthermore, some additional physiological mechanism can lead to the activation of macrophages. For these latest, the regulatory T cells (Treg), the Fcγ receptors, the apoptotic cells and the prostaglandins are increasing the number of macrophages involved in the regulation of inflammation and antitumour defences [84]. These inflammatory mediators are involved in activating anti-microbial defence mechanisms, including oxidative processes that contribute to killing pathogens and the secreted IL-12 and IL-23. These direct the differentiation and expansion of anti-microbial TH1 and TH17 cells that help to drive inflammatory responses [85]. Recent research shows that intestinal antigen-presenting cells can be divided into CD11c+ CD11b− , CD11c+ CD11b+ and CD11cdullCD11b+ categories. Particularly, the CD11cdullCD11b+ cells are CD103− F4/80+ macrophages, with efficient role in inducing the Foxp3+ regulatory T (Treg) cells [86]. Tumour cells affect the surrounding cellular environment by promoting tumour growth and metastasis by establishing a tumour microenvironment that is conducive to tumour development [87–90]. In the tumour microenvironment, tumour cells secrete inflammatory cytokines, such as TGFβ and IL-10. These cytokines stimulate differentiation of regulatory T and Treg cells [91, 92] as well as differentiation of tumour-associated macrophages (TAMs) into M2 macrophages. This causes the host immune system to locate and attack cancer cells, which generates subsequent tumour cell evasion of this immune surveillance and attack, which enhances tumour growth and metastasis [87, 93–98]. Various cytokines, chemokines and growth factors in the tumour microenvironment are the primary elements that affect the host's anti-tumour ability and evasion of tumour cells [89, 99]. Tumour microenvironments are complicated cellular microcosms [89, 97], and numerous immune cells are located throughout tumour microenvironments. Macrophages are the most crucial and abundant immune cells in the tumour microenvironment. The two most critical types of macrophages, based on function and differentiation, are M1 and M2 macrophages. M1 macrophages are characterised by tumour

**Figure 3.** The cooperation of the antigen-presenting cells, costimulatory molecules, and cytokines. Bacterial infection innately activates macrophages, causing the secretion of pro-inflammatory cytokines, such as TNF-α, IL-6, and IL-1β. This promotes peripheral insulin resistance and reduces nutrient storage during the metabolic reaction. Furthermore, several additional mechanisms can also contribute to the activation of macrophages for immune-regulatory activity.

resistance, whereas M2 macrophages are characterised by tumour promotion [98, 100]. In mouse models, macrophages present CD11b, F4/80, CSF-1R and F4/80 as the surface proteins for M1 and M2 macrophages [93, 101]. Recent studies have noted large quantities of TAMs in tumour tissue. TAMs are the most abundant and critical immune cells in the tumour microenvironment [102–104] and are the main factors that enable the tumour microenvironment to exert immune inhibitory effects [101, 102]. In the tumour microenvironment, tumour cells and the surrounding stoma cells secrete cytokines and growth factors that stimulate TAMs and activate the various expression, function, receptor regulation and secretion types of chemokines [103, 105], including anti-tumour M1 macrophages and pro-tumour M2 macrophages [98, 106–108]. In the tumour microenvironment, the proportions of M1 and M2 macrophages are unequal. Tumour microenvironments contain large amounts of transmitters, such as M-CSF, IL-6, IL-10, TGF-β and COX-2, that induce transformation of TAMs into M2 macrophages that secrete immune inhibitory chemokines and have poor antigen-presenting and cytotoxic abilities, which generates tumour growth and metastasis [49, 98, 102–104, 109–114]. M2 macrophages and TAMs have protumour and immune inhibitory effects, secrete large amounts of IL-10, TGF-β, CCL17 and CCL22, attract non-cytotoxic Treg and TH2 cells to aggregate in tumour tissue, inhibit T-cell differentiation and function, lower cytotoxic T-cell function, induce T-cell apoptosis, secrete CCL18 and attract naïve T cells [49, 98, 115]. NADPH oxidase is a major enzymatic source of cellular ROS. NADPH plays a fundamental role in maintaining normal cell functions. Recent research has focussed on this enzyme's role in cellular oxidative stress, which may eventually contribute to various pathophysiological conditions and diseases [27, 28]. Studies have found that NADPH oxidase modulates multiple redox-sensitive intra-cellular signalling pathways by generating ROS molecules. This modulation includes inhibition of protein tyrosine phosphatases and activation of certain redoxsensitive transcription factors [116, 117]. ROS consist of numerous molecular species, including H2O2, oxide ions (O2 − ) and OH−29, that act as signalling molecules involved in the migration of hepatic profibrogenic cells [118] and the functioning of peripheral blood monocytes [119]. ROS and RNS, generated endogenously or in response to environmental stress, have long been implicated in tissue injury for a variety of disease states [120, 121]. Stimulation of the mitochondrial apoptotic pathway through ROS and mitochondrial DNA damage promotes outer membrane permeabilisation, which triggers caspase-dependent or caspaseindependent cytosolic signalling events [122]. Activated inflammatory cells serve as sources of ROS and RNS that can initiate the alteration of the cell function, gathering specific cellular signalling, transcription factor activation, physiological factors release, the apoptosis process and compensatory cell proliferation. However, it remains unclear whether the ROS or the RNS production and release through neutrophils or macrophages enhance sufficient diffusion into the intra-cellular cytoplasm as to affect the cellular response [123, 124].

### **7. Wound healing**

physiological mechanism can lead to the activation of macrophages. For these latest, the regulatory T cells (Treg), the Fcγ receptors, the apoptotic cells and the prostaglandins are increasing the number of macrophages involved in the regulation of inflammation and antitumour defences [84]. These inflammatory mediators are involved in activating anti-microbial defence mechanisms, including oxidative processes that contribute to killing pathogens and the secreted IL-12 and IL-23. These direct the differentiation and expansion of anti-microbial TH1 and TH17 cells that help to drive inflammatory responses [85]. Recent research shows that

affect the surrounding cellular environment by promoting tumour growth and metastasis by establishing a tumour microenvironment that is conducive to tumour development [87–90]. In the tumour microenvironment, tumour cells secrete inflammatory cytokines, such as TGFβ and IL-10. These cytokines stimulate differentiation of regulatory T and Treg cells [91, 92] as well as differentiation of tumour-associated macrophages (TAMs) into M2 macrophages. This causes the host immune system to locate and attack cancer cells, which generates subsequent tumour cell evasion of this immune surveillance and attack, which enhances tumour growth and metastasis [87, 93–98]. Various cytokines, chemokines and growth factors in the tumour microenvironment are the primary elements that affect the host's anti-tumour ability and evasion of tumour cells [89, 99]. Tumour microenvironments are complicated cellular microcosms [89, 97], and numerous immune cells are located throughout tumour microenvironments. Macrophages are the most crucial and abundant immune cells in the tumour microenvironment. The two most critical types of macrophages, based on function and differentiation, are M1 and M2 macrophages. M1 macrophages are characterised by tumour

**Figure 3.** The cooperation of the antigen-presenting cells, costimulatory molecules, and cytokines. Bacterial infection innately activates macrophages, causing the secretion of pro-inflammatory cytokines, such as TNF-α, IL-6, and IL-1β. This promotes peripheral insulin resistance and reduces nutrient storage during the metabolic reaction. Furthermore, several additional mechanisms can also contribute to the activation of macrophages for immune-regulatory activity.

CD11b−

cells are CD103−

regulatory T (Treg) cells [86]. Tumour cells

, CD11c+

CD11b+

F4/80+

and

macro-

intestinal antigen-presenting cells can be divided into CD11c+

phages, with efficient role in inducing the Foxp3+

174 Wound Healing - New insights into Ancient Challenges

categories. Particularly, the CD11cdullCD11b+

CD11cdullCD11b+

Immune cells are involved in virtually every aspect of the wound repair process, from the initial stages, where they participate in haemostasis and work to prevent infection, to later stages where they drive scar formation [125, 126]. T lymphocytes exercise crucial in vivo effects on various parameters of healing [127–129]. Neutrophils help control infection during wound healing, but they also release harmful enzymes that damage healthy tissue surrounding the wound site [130–132]. Recent researchers have noted that several specific proteins produced by wound macrophages at the site of injury are involved: (1) in the recruitment and activation of additional macrophages infiltrating in the wound; (2) in the production of growth factors that promote cellular proliferation and tissue recovery synthesis; (3) in stimulating proteases and extra-cellular matrix growth and (4) in the process of tissue remodelling [133]. β-catenindependent Wnt pathways, which are classified according to their ability to promote stabilisation of β-catenin in the cytoplasm, act as cellular signals through cytoplasmic stabilisation and accumulation of β-catenin in the nucleus to activate gene transcription [134]. This could enhance wound healing by lymphocytes [135, 136]. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase modulates multiple redox-sensitive intra-cellular signalling pathways by generating ROS molecules. This includes inhibiting protein tyrosine phosphatases and activating certain redox-sensitive transcription factors [116, 137, 138]. This shows that ROS regulate the expression of key chemical mediators that further modulate the inflammatory response in animal models; it has also been reported that these redox-sensitive processes may include cytokine action, angiogenesis, cell motility and extra-cellular matrix formation [139–141]; this can enable reliable estimates of wound-healing capacity, which is altered by various conditions, such as inflammation. Furthermore, research on one of the ROS has indicated that H2O2 plays a critical role in wound repair, inflammation and anti-inflammation mechanisms [142, 143]. Our published research also showed that the production of ROS (i.e., H2O2 after an injury has occurred) may cause healing to generate inflammation through the apoptosis of the cell. Over-inhibition of NADPH oxidase activity may reduce the normal progress of apoptosis under the wound and might delay healing [29].

Inflammation enhances vascular permeability, active migration of blood cells and the passage of plasma constituents into the injured tissue [144]. Blood leukocytes actively participate in the defence and inflammation responses, being activated since the earliest phases of atherosclerosis process. Inflammation and atherosclerosis shelter intricate mechanisms relied to leukocytes recruitment [145]. Neuro-inflammation mediators are described to be closely related to brain cells functioning (such as microglia and astrocytes), to the complement system activation and to cytokines, and chemokines production [146]. Regarding cancer development [147], proinflammatory cytokines, including IL-1α, IL-1β, IL-6, IL-8, IL-18, chemokines, matrix metallopeptidase-9 and vascular endothelial growth factor, are primarily regulated by the transcription NF-κB, which is active in most tumours and is induced by carcinogens [148]. Cutaneous wound repair is a tightly regulated and dynamic process involving blood clotting, inflammation, formation of new tissue and tissue remodelling [149]. Thrombin is the protease involved in blood coagulation. Its deregulation can cause haemostatic abnormalities, which range from subtle subclinical problems to serious life-threatening coagulopathies (i.e., during septicaemia) [150]. Inflammation and coagulation are both parts of the natural mechanism that protects the organism against infection. The endothelial cells and the platelets are capable to react in the acute, also in the chronic inflammatory environment. They release pro-inflammatory mediators that produce adhesion of molecules, proteases and clotting factors associated to leukocytes recruitment [151]. The elements of the PAR family serve as sensors that detect blood-clotting serine proteinases in the inflamed target cells. Activation of PAR-1 by thrombin and of PAR-2 by other factors on the membrane of endothelial cells generates rapid expression and exposure of adhesive proteins that mediate an acute inflammatory reaction and of the tissue factor that initiates the blood coagulation cascade [152] as presented as **Figure 4**.

stages where they drive scar formation [125, 126]. T lymphocytes exercise crucial in vivo effects on various parameters of healing [127–129]. Neutrophils help control infection during wound healing, but they also release harmful enzymes that damage healthy tissue surrounding the wound site [130–132]. Recent researchers have noted that several specific proteins produced by wound macrophages at the site of injury are involved: (1) in the recruitment and activation of additional macrophages infiltrating in the wound; (2) in the production of growth factors that promote cellular proliferation and tissue recovery synthesis; (3) in stimulating proteases and extra-cellular matrix growth and (4) in the process of tissue remodelling [133]. β-catenindependent Wnt pathways, which are classified according to their ability to promote stabilisation of β-catenin in the cytoplasm, act as cellular signals through cytoplasmic stabilisation and accumulation of β-catenin in the nucleus to activate gene transcription [134]. This could enhance wound healing by lymphocytes [135, 136]. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase modulates multiple redox-sensitive intra-cellular signalling pathways by generating ROS molecules. This includes inhibiting protein tyrosine phosphatases and activating certain redox-sensitive transcription factors [116, 137, 138]. This shows that ROS regulate the expression of key chemical mediators that further modulate the inflammatory response in animal models; it has also been reported that these redox-sensitive processes may include cytokine action, angiogenesis, cell motility and extra-cellular matrix formation [139–141]; this can enable reliable estimates of wound-healing capacity, which is altered by various conditions, such as inflammation. Furthermore, research on one of the ROS has indicated that H2O2 plays a critical role in wound repair, inflammation and anti-inflammation mechanisms [142, 143]. Our published research also showed that the production of ROS (i.e., H2O2 after an injury has occurred) may cause healing to generate inflammation through the apoptosis of the cell. Over-inhibition of NADPH oxidase activity may reduce the

176 Wound Healing - New insights into Ancient Challenges

normal progress of apoptosis under the wound and might delay healing [29].

Inflammation enhances vascular permeability, active migration of blood cells and the passage of plasma constituents into the injured tissue [144]. Blood leukocytes actively participate in the defence and inflammation responses, being activated since the earliest phases of atherosclerosis process. Inflammation and atherosclerosis shelter intricate mechanisms relied to leukocytes recruitment [145]. Neuro-inflammation mediators are described to be closely related to brain cells functioning (such as microglia and astrocytes), to the complement system activation and to cytokines, and chemokines production [146]. Regarding cancer development [147], proinflammatory cytokines, including IL-1α, IL-1β, IL-6, IL-8, IL-18, chemokines, matrix metallopeptidase-9 and vascular endothelial growth factor, are primarily regulated by the transcription NF-κB, which is active in most tumours and is induced by carcinogens [148]. Cutaneous wound repair is a tightly regulated and dynamic process involving blood clotting, inflammation, formation of new tissue and tissue remodelling [149]. Thrombin is the protease involved in blood coagulation. Its deregulation can cause haemostatic abnormalities, which range from subtle subclinical problems to serious life-threatening coagulopathies (i.e., during septicaemia) [150]. Inflammation and coagulation are both parts of the natural mechanism that protects the organism against infection. The endothelial cells and the platelets are capable to react in the acute, also in the chronic inflammatory environment. They release pro-inflammatory mediators that produce adhesion of molecules, proteases and clotting factors associated

**Figure 4.** Wound healing was initiated after the injury of the cell, tissue even the organ. In the early stage of the healing, the damaged tissue producing a lot of ROS leading to neighbour cells into the apoptosis, following the apoptotic cells collapsed and released caspases were able to induce the tissue repair. However, the imbalance inflammatory may induce over-production of blood glucose that is leading to decrease the EGF receptor expression further to impair the wound healing.
