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Inhibition of TLR4 protects rat islets against lipopolysaccharide-induced dysfunction
Xiao Wang1, Qin Min Ge1, Fan Bian2
1Department of Emergency, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, P.R. China.
Abstract:
Oxidative stress leads to dysfunction in pancreatic cells, causing a reduction in insulin secretion following exposure to glucose. Toll-like receptor 4 (TLR4) may be activated by exposure to lipopolysaccharide (LPS) stress. TLR4 may mediate the initiation of inflammatory and immune defense responses; however, the importance of the LPS/TLR4 interaction in apoptosis induced by oxidative stress in pancreatic β cells remains to be elucidated. The present study aimed to investigate the importance of TLR4 during LPS‑induced oxidative stress, apoptosis and dysfunction of insulin secretion in isolated islets of rats. LPS‑induced stimulation of TLR4 increased the production of reactive oxygen species and promoted apoptosis by upregulating the expression levels of caspase‑3, poly ADP ribose polymerase and altering the expression ratio of B‑cell lymphoma‑2 (Bcl‑2)/Bcl‑2 associated X protein. Additionally, the insulin secretion of islets cells was reduced. Anti‑TLR4 antibody and a knockdown of TLR4 by TLR4‑short hairpin RNA were used to inhibit TLR4 activity, which may reverse LPS‑induced events. The present study determined that in islets exposed to LPS oxidative stress, dysfunction may be partly mediated via the TLR4 pathway. Inhibition of TLR4 may prevent dysfunction of rat islets due to oxidative stress. The present study revealed that targeting the LPS/TLR4 signaling pathway and antioxidant therapy may be a novel treatment for the severely septic patients with hyperglycemia stress.
Insights
Lipopolysaccharide (LPS) stress activates Toll-like receptor 4 (TLR4), causing pancreatic beta cell dysfunction and reduced insulin secretion. Inhibiting TLR4 may protect against LPS-induced oxidative stress and apoptosis in islets.
Area of Science:
- Endocrinology
- Immunology
- Cell Biology
Background:
- Oxidative stress impairs pancreatic beta cell function, reducing insulin secretion.
- Toll-like receptor 4 (TLR4) activation by lipopolysaccharide (LPS) is implicated in inflammatory responses.
- The role of LPS/TLR4 in oxidative stress-induced pancreatic beta cell apoptosis is unclear.
Purpose of the Study:
- To investigate the role of TLR4 in LPS-induced oxidative stress, apoptosis, and insulin secretion dysfunction in rat islets.
- To determine if inhibiting TLR4 can mitigate these LPS-induced effects.
Main Methods:
- Isolated rat islets were exposed to LPS to stimulate TLR4.
- Apoptosis markers (caspase-3, PARP, Bcl-2/Bax ratio) and reactive oxygen species (ROS) production were measured.
- Insulin secretion was assessed.
- TLR4 activity was inhibited using anti-TLR4 antibody and TLR4-short hairpin RNA (shRNA).
Main Results:
- LPS stimulation of TLR4 increased ROS production and promoted apoptosis.
- LPS exposure upregulated caspase-3 and PARP, and altered the Bcl-2/Bax ratio.
- Insulin secretion from islets was significantly reduced following LPS exposure.
- Inhibition of TLR4 reversed LPS-induced oxidative stress, apoptosis, and insulin secretion dysfunction.
Conclusions:
- The LPS/TLR4 pathway partly mediates oxidative stress, apoptosis, and dysfunction in rat islets.
- Inhibiting TLR4 may prevent LPS-induced islet dysfunction.
- Targeting the LPS/TLR4 pathway combined with antioxidant therapy could be a novel treatment for hyperglycemia in septic patients.
