Inflammation is the host's physiological response to pathogen invasion and tissue damage. It is essential for survival, but at the same time, if not kept under control by endogenous mechanisms, can cause serious morbidity, both acute and chronic. It is well established that immune system can be no longer regarded as entirely autonomous in its regulation. Neuronal activities, by means of neurotransmitters' release, regulate the host's inflammatory response against pathogens infection and injury. One of these mechanism relies on a reflex arc called the "Cholinergic anti-inflammatory pathway"1, by which the afferent component of the vagus nerve carries information about the inflammatory processes that occur at the peripheral level. The efferent fibres of the same nerve, releasing acetylcholine (ACh), reduce the level of pro-inflammatory cytokines produced by innate immune cells. Various studies have shown that the ?7 nicotinic receptor (CHRNA7) is a key element for the functioning of this pathway. Recently, CHRFAM7A gene was discovered2. It is the product of a recombination event that occurred in human where the portion of CHRNA7 gene, from exon 5 to 10, fused to a novel gene (FAM7A) which encodes four novel exons A, B, C from the serine/threonine kinase ULK4 gene, mapping to 3p22.1, and exon D of unknown provenance. CHRFAM7A gene is located on chromosome 15 (15q13-q14 region), 1.6 Mb apart from CHRNA7 gene, in the direction of the centromere, and in the opposite orientation with respect to CHRNA7. Recently, our laboratory has shown that LPS treatment of a human leukaemic monocytic cell line (THP-1) down-regulated the expression of the CHRFAM7A gene, mainly by a transcriptional mechanism reliant on NF-?B3. This mechanism was confirmed in primary cultures of macrophages which unlike THP-1 express also CHRNA7. Treatment with LPS induces the expression of the CHRNA7 gene suggesting that in these cells CHRFAM7A may participate specifically in the innate immune system's inflammatory response by acting as a dominant negative regulator of the ?7 nicotinic receptor, a hypothesis formulated independently by other laboratories4, 5. Many recent reports6-8 have shown that the symptoms of chronic inflammatory disease can be alleviated by means of treatment with anti-TNF? antibodies or nicotine; however, the fact that trials of nicotine therapy have often been characterised by excessive side effects due to a lack of specificity for just one receptor type, underlines the importance of understanding the mechanisms of regulation of ?7 and its duplicated isoform subunits in response to pro-inflammatory stimuli, to gain further insight into their role in the immune system and the cholinergic anti-inflammatory pathway, and greatly improve the discovery of anti-inflammatory treatments. In order to study the role of CHRFAM7A in the "Cholinergic anti-inflammatory pathway" we decided to isolate and characterize the CHRFAM7A 5' flanking region, which, to date, is unknown. The gene encoding CHRFAM7A is expressed both in cells of innate immunity and in neuronal cells; experiments in two cell models, a human monocytic cell line (THP-1), and a neuroblastoma cell line (SH-SY5Y) revealed the presence of different regulatory regions important for proper CHRFAM7A gene expression in different tissues.
The regulatory regions of the CHRFAM7A gene, the alpha7 nicotinic acetylcholine receptor subunit duplicate form, involved in the cholinergic anti-inflammatory pathway
R Benfante
2014
Abstract
Inflammation is the host's physiological response to pathogen invasion and tissue damage. It is essential for survival, but at the same time, if not kept under control by endogenous mechanisms, can cause serious morbidity, both acute and chronic. It is well established that immune system can be no longer regarded as entirely autonomous in its regulation. Neuronal activities, by means of neurotransmitters' release, regulate the host's inflammatory response against pathogens infection and injury. One of these mechanism relies on a reflex arc called the "Cholinergic anti-inflammatory pathway"1, by which the afferent component of the vagus nerve carries information about the inflammatory processes that occur at the peripheral level. The efferent fibres of the same nerve, releasing acetylcholine (ACh), reduce the level of pro-inflammatory cytokines produced by innate immune cells. Various studies have shown that the ?7 nicotinic receptor (CHRNA7) is a key element for the functioning of this pathway. Recently, CHRFAM7A gene was discovered2. It is the product of a recombination event that occurred in human where the portion of CHRNA7 gene, from exon 5 to 10, fused to a novel gene (FAM7A) which encodes four novel exons A, B, C from the serine/threonine kinase ULK4 gene, mapping to 3p22.1, and exon D of unknown provenance. CHRFAM7A gene is located on chromosome 15 (15q13-q14 region), 1.6 Mb apart from CHRNA7 gene, in the direction of the centromere, and in the opposite orientation with respect to CHRNA7. Recently, our laboratory has shown that LPS treatment of a human leukaemic monocytic cell line (THP-1) down-regulated the expression of the CHRFAM7A gene, mainly by a transcriptional mechanism reliant on NF-?B3. This mechanism was confirmed in primary cultures of macrophages which unlike THP-1 express also CHRNA7. Treatment with LPS induces the expression of the CHRNA7 gene suggesting that in these cells CHRFAM7A may participate specifically in the innate immune system's inflammatory response by acting as a dominant negative regulator of the ?7 nicotinic receptor, a hypothesis formulated independently by other laboratories4, 5. Many recent reports6-8 have shown that the symptoms of chronic inflammatory disease can be alleviated by means of treatment with anti-TNF? antibodies or nicotine; however, the fact that trials of nicotine therapy have often been characterised by excessive side effects due to a lack of specificity for just one receptor type, underlines the importance of understanding the mechanisms of regulation of ?7 and its duplicated isoform subunits in response to pro-inflammatory stimuli, to gain further insight into their role in the immune system and the cholinergic anti-inflammatory pathway, and greatly improve the discovery of anti-inflammatory treatments. In order to study the role of CHRFAM7A in the "Cholinergic anti-inflammatory pathway" we decided to isolate and characterize the CHRFAM7A 5' flanking region, which, to date, is unknown. The gene encoding CHRFAM7A is expressed both in cells of innate immunity and in neuronal cells; experiments in two cell models, a human monocytic cell line (THP-1), and a neuroblastoma cell line (SH-SY5Y) revealed the presence of different regulatory regions important for proper CHRFAM7A gene expression in different tissues.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
