Inflammation is the body's natural response to harmful stimuli, such as cell surface receptors, bacteria, or viruses (Nordqvist, 2015). These foreign stimuli trigger the immune response, which allow for increased blood flow to the inflamed site (MedlinePlus). The increased blood flow carries immune cells to the inflammatory site in order to kill off invaders and clean up dead cells (Wallach et al., 2013; Hochreiter-Hufford & Ravichandran, 2013). Inflammation is characterized by the Latin phrase, "calor, dolor, rubor, and tumor," which means heat, pain, redness, and swelling (Ciaccia L et al. 2011).
GRANZYME B & CHRONIC INFLAMMATION ("The Secret Killer")
While inflammation is normally a beneficial and even essential part of the immune response, chronic inflammation (also known as prolonged inflammation) is associated with a multitude of different diseases, such as diabetes, heart diseases, arthritis, prolonged wound healing, autoimmune diseases, and even various cancers (Russell, 2014; Cullen et al., 2010). In fact, due to its role in various diseases, chronic inflammation become known as the Secret Killer (Gibbons, 2012; Figure 1).
Chronic inflammation begins when the normal immune response is stimulated, but the immune cells do not shut down on cue. These immune cells become hyperactive and interfere with healthy cells and tissues, which ultimately results in tissue damage.
GzmB, a serine protease, is an essential part of the immune system that is overexpressed during inflammation, (Granville et al., 2010). GzmB is normally produced by T cells and natural killer cells during inflammation, and can recognize and enter tumor cells to induce apoptosis. We refer to this important immune role as GzmB's intracellular function. Outside of cells, GzmB is also capable of cleaving proteins in the extracellular matrix (ECM) (Ida et al., 2005). The ECM is a collection of proteins that exists outside of cells and functions to provide both structure and support for cells and tissues. GzmB activity outside of the cells is to cleave around tumor cells, thereby jeopardizing tissue integrity and causing the death of tumor cells (Buzza et al., 2005). We refer to this as GzmB’s extracellular function.
GzmB levels are elevated during chronic inflammation, which leads to excess cleavage of important proteins in the ECM, and ultimately results in tissue damage (Figure 2) and various diseases (Hiebert & Granville, 2012) (Figure 3). For example, increased GzmB cleavage of cartilage proteoglycan leads to and worsens rheumatoid arthritis; and excess cleavage of ECM fibronectin, vitronectin, or decorin prolongs wound healing and contributes to photoaging (Hiebert et al., 2013).
Our project aim is to prevent tissue damage from chronic inflammation by limiting GzmB activity in the ECM without affecting its intracellular functions.
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