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Advanced Glycation End Products Impair Ca2+ Mobilization and Sensitization in Colonic Smooth Muscle Cells via the
Background/Aims:
Excessive production of advanced glycation end products (AGEs) has been implicated in diabetes-related complications. This study aimed to investigate the mechanism by which AGEs potentially contribute to diabetes-associated colonic dysmotility.
Methods:
Control and streptozotocin (STZ)-induced diabetic groups were treated with aminoguanidine (AG). The colonic transit time and contractility of circular muscle strips was measured. ELISA, immunohistochemistry and western blotting were used to measure Nε-carboxymethyl-lysine (CML) levels. Primary cultured colonic smooth muscle cells (SMCs) were used in complementary in vitro studies.
Results:
Diabetic rats showed prolonged colonic transit time, weak contractility of colonic smooth muscle strips, and elevated levels of AGEs in the serum and colon tissues. cAMP levels, protein kinase-A (PKA) activities, and inositol 1,4,5-trisphosphate receptor type 3 (IP3R3) phosphorylation were increased in the colon muscle tissues of diabetic rats, whereas RhoA/Rho kinase activity and myosin phosphatase target subunit 1 (MYPT1) phosphorylation were reduced. The inhibition of the production of AGEs (AG treatment) reduced these effects. In cultured colonic SMCs, AGE-BSA treatment increased IP3R3 phosphorylation and reduced intracellular Ca2+ concentration, myosin light chain (MLC) phosphorylation, RhoA/Rho kinase activity, and MYPT1 phosphorylation. The PKA inhibitor H-89 and anti-RAGE antibody inhibited the AGE-BSA-induced impairment of Ca2+ signaling and cAMP/PKA activation.
Conclusion:
AGEs/RAGE participate in diabetes-associated colonic dysmotility by interfering with Ca2+ signaling in colonic SMCs through targeting IP3R3-mediated Ca2+ mobilization and RhoA/Rho kinase-mediated Ca2+ sensitization via the cAMP/PKA pathway.
Insights
Advanced glycation end products (AGEs) contribute to diabetic colonic dysmotility by disrupting smooth muscle cell signaling. Aminoguanidine treatment mitigated these effects, suggesting a therapeutic target.
Area of Science:
- Gastroenterology
- Endocrinology
- Cellular Biology
Background:
- Advanced glycation end products (AGEs) are implicated in diabetes complications.
- Diabetes is associated with gastrointestinal dysmotility, including in the colon.
Purpose of the Study:
- To investigate the mechanism by which AGEs contribute to diabetes-associated colonic dysmotility.
- To explore the role of AGEs in colonic smooth muscle cell (SMC) function.
Main Methods:
- Streptozotocin (STZ)-induced diabetic rat model treated with aminoguanidine (AG).
- Assessment of colonic transit time and ex vivo colonic muscle contractility.
- Measurement of AGEs (Nε-carboxymethyl-lysine, CML) via ELISA, immunohistochemistry, and Western blotting.
- In vitro studies using primary cultured colonic SMCs treated with AGE-bovine serum albumin (AGE-BSA).
Main Results:
- Diabetic rats exhibited prolonged colonic transit, reduced muscle contractility, and elevated AGEs.
- AGEs altered intracellular signaling pathways, including increased cAMP/PKA and IP3R3 phosphorylation, and decreased RhoA/Rho kinase activity.
- AG treatment reversed these diabetic effects.
- In vitro, AGE-BSA impaired Ca2+ signaling and SMC function, effects inhibited by PKA inhibitor and anti-RAGE antibody.
Conclusions:
- AGEs, via the RAGE receptor, contribute to diabetes-associated colonic dysmotility.
- AGEs interfere with colonic SMC Ca2+ signaling by targeting IP3R3 and RhoA/Rho kinase pathways.
- The cAMP/PKA pathway is involved in AGE-induced colonic smooth muscle dysfunction.