hCLOCK induction by hypoxia promotes inflammatory responses by activating the NF‑κB pathway

Area of Science:

• Molecular Biology
• Cell Biology
• Immunology

Background:

• Hypoxia is known to induce inflammation-associated cytokines.
• The Circadian locomotor output cycles protein kaput (CLOCK) pathway activates nuclear factor-kappa B (NF-κB), a key transcription factor in hypoxia.
• The role of the NF-κB pathway in CLOCK-induced inflammation requires further elucidation.

Purpose of the Study:

• To investigate the role of the NF-κB pathway in the CLOCK-induced inflammatory response under hypoxic conditions.
• To determine if inhibiting NF-κB affects the expression of proinflammatory cytokines induced by CLOCK during hypoxia.

Main Methods:

• Utilized human umbilical vein endothelial cells (HUVECs) under hypoxic and control conditions.
• Employed small hairpin RNA (shRNA) to silence CLOCK expression.
• Administered pyrrolidine dithiocarbamate (PDTC) to inhibit NF-κB activity.

Main Results:

• Hypoxia significantly increased NF-κB and proinflammatory cytokine expression (IL-1, IL-1β, IL-6, ICAM-1, COX-2, TNF-α).
• CLOCK silencing reversed these increases under hypoxia.
• NF-κB inhibition with PDTC reduced cytokine expression and abolished the CLOCK-induced inflammatory response.

Conclusions:

• CLOCK induces inflammation primarily through the activation of the NF-κB signaling pathway.
• The NF-κB pathway is a critical mediator of CLOCK-driven inflammation in response to hypoxia.
• Targeting the CLOCK-NF-κB axis may offer therapeutic strategies for hypoxia-related inflammatory diseases.