BIOCHEMICAL AND HISTOPATHOLOGICAL EFFECTS OF CATECHIN ON EXPERIMENTAL PERIPHERAL NERVE INJURIES

AIm:Catechin is a type of polyphenol, which along with epicatechin, epigallocatechin, and epigallocatechin-gallate (EGCG). This study aims to investigate the effect of EGCG, a major metabolite of catechin, which is the principle bioactive compound in green tea, on rats with peripheral nerve injury.

Method:A total of 74 rats were divided into six groups, namely the control, the trauma, the normal saline, a 25 mg/kg EGCG, a 50 mg/kg EGCG and a daily consumption group (10 mg/kg EGCG was given intraperitoneally for 14 days before the trauma). Except the first group, other groups underwent a 1-minute sciatic nerve compression by clip with 50 gr/cm2 pressure. Nerve samples were obtained at day 28 after trauma for the biochemical and histopathological analysis

Results:Our study showed that Daily consumption, 25 mg/kg EGCG and 50 mg/kg EGCG groups demonstrated statistically significant decreased lipid peroxidation levels and particularly daily consumption, and 25 mg/kg EGCG groups showed a favourable reduction of degeneration and edema histologically

ConclusIon:This study shows that Catechin and its derivatives have a protective effect on peripheral nerve injury.

Keywords:Axonal degeneration, Epigallocatechin-gallate, Electron microscope, Light microscope, Lipid peroxidation, Peripheral nerve injury

INTRODUCTIONPeripheral nerve injury causes loss in the labor force, economic loss and psychological problems. It is a topic of much interest, due to lack of available treatment options. The severity of a nerve compression lesion depends on several factors, including compression pressure, length of pressure, and the area which the pressure affects. Neuronal tissue damage continues after the compression is resolved (25). Compression injury to the nerve induces Wallerian degeneration and axon regeneration, whereas after central nervous system (CNS) injury axons fail to regenerate. These findings were first described by Ramon Y. Cajal under light microscope examinations in 1928 (33). Similarly, the process has also been shown by electron microscopic studies. The post-traumatic nerve tissue changes, observed by electron microscope, include intracytoplasmic edema, and changes in the nucleus, mitochondria, axon and myelin sheath (24).Similar to the blood–brain barrier in the CNS, there is a blood–nerve barrier in the peripheral nervous system. The blood-nerve barrier regulates the endoneurial microenvironment. Many studies have examined the effect of local experimental compression and intraneural microcirculation, and concluded that 20 – 30 mm Hg external pressure induces a blockage of venous blood flow in the epineurium. Pressure of 80 mm Hg leads to complete cessation of intraneural blood flow (19).

Injury to a peripheral nerve triggers an initiation of a response that incorporates a sequence of biochemical alterations. Severe injury can lead to neuronal edema, more intense neutrophil infiltration, and apoptosis. Increased neutrophil infiltration, myeloperoxidase activity, and the level of tissue malondialdehyde (MDA) lead to an increased level of lipid peroxidation (15). Lipid peroxidation is a toxic process and a self-propagating chain-reaction (6, 15). Lipid peroxidation can impair membrane function directly and damage cell components indirectly. A marked increase in lipid peroxidation is observed after injury. Hall and Braugler reported that lipid peroxidation increases to a peak level at 1, 24 and 48 hours after spinal cord trauma (17)The tea plant, Camellia sinensis, is a member of the Theaceae family (4, 14, 37). Tea leaves contain polyphenol and polyphenol oxidase enzymes. The main component of green tea extract polyphenol is called catechins. Black tea contains 250 mg/L of catechin, compared to green tea which contains 420 mg/L (40). Approximately 25-35% of the dry weight of tea leaves is catechins. A single cup of green tea contains 100-200 milligrams of catechin (39, 41). The anticancer, antitumor, antimutagenic, chemopreventive, antiproliferative, antiinflammatory, antioxidant, antidiabetic, antiallergic, antihypertensive, antiplatelet, antiobesity, hypocholesterolemic, and neuroprotective effects of catechins have been shown in various in vivo and in vitro studies (36).The flavonoids contain a double bond and eight isomers. The main catechin group consists of eight polyphenolic flavonoid- type compounds, namely, catechin (C), epicatechin (EC), gallo-catechin (GC), epigallo-catechin (EGC), catechin-gallate (CG), epicatechin-gallate (ECG), gallocatechin-gallate (GCG) and epigallocatechin gallate (EGCG). EGCG is the most prominent flavonoid compound in tea leaves, and has the highest antioxidant activity of all the green tea catechins (ECG > EGCG > EGC > EC) (1, 7, 8, 27, 28, 32). Tea catechins and polyphenols are effective scavengers of physiologically relevant reactive oxygen and nitrogen species, including superoxide, peroxyl radicals, singlet oxygen, and peroxynitrite (10, 13, 16, 29).The best treatment approach for peripheral nerve injuries remains unclear. In the treatment of peripheral nerve injury, non-steroidal anti-inflammatory and steroids can be used to reduce inflammation, and nerve growth factors, thyroid hormones, growth hormone, ACTH, and insulin like peptides to improve regeneration (11, 20, 31, 35, 38). The aim of this study was to examine favourable antioxidant and anti-inflammatory effects of catechin on peripheral nerve injury.