Carvacrol abates NLRP3 inflammasome activation by augmenting Keap1/Nrf-2/p62 directed autophagy and mitochondrial quality control in neuropathic pain

ABSTRACT

Objectives: We aimed to evaluate the effect of carvacrol (CRC), a phenolic monoterpene with high nutritional value on NLRP3 activation against chronic constriction injury (CCI) of sciatic nerve induced neuropathic pain (NP) in rats and in lipopolysacharide (LPS) induced neuroinflammation in neuro2a (N2A) cells. Methods: NP was induced in male SD rats by performing CCI and CRC (30 and 60 mg/kg, p.o) was administered for 14 days. Behavioural and functional parameters were evaluated using standard procedures. Various molecular experimentations were conducted to evaluate the efficacy of CRC against CCI induced neuropathy and in LPS (1 μg/ml) primed and ATP (5 μM) treated N2A cells.

Results: CCI resulted in marked development of hyperalgesia and allodynia. Further, CCI rats, LPS and ATP treated N2A cells showed enhanced expression of NLRP3, ASC, Caspase-1 and IL-1β. In addition, CCI rats exhibited diminished levels of Nrf-2 with an increase in Keap1 expression. Also, CCI animals manifested with compromised mitochondrial function along with decreased autophagy markers and enhanced p62 levels when compared to sham rats. However, CRC administration significantly ameliorated these changes suggesting NLRP3 inhibition by CRC may be attributed to activation of autophagy via Keap1/Nrf-2/p62 forward feedback loop and augmentation of mitochondrial quality control. Intriguingly, pretreatment of CRC (50 and 100 μM) to LPS and ATP treated N2A cells resulted in decreased colocalization of NLRP3 and ASC.

Discussion: These findings revealed the neuroprotective potential of CRC against CCI induced NP and delineate the critical role of autophagy and mitochondrial quality control in NLRP3 regulation.

KEYWORDS:

• Carvacrol
• NLRP3
• neuropathic pain
• autophagy
• mitochondrial quality control
• CCI
• neuroinflammation
• neuro2A cells

Data availability statement

The data that support the findings of this study are available on request from the corresponding author upon reasonable request.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Vijay Kumar Arruri

Vijay Kumar Arruri is pursuing PhD degree at National Institute of Pharmaceutical education and research, Hyderabad, India. His doctoral research is focused on elucidating the molecular mechanisms of NLRP3 regulation and its implication in neuropathic pain.

Chayanika Gundu

Chayanika Gundu is pursuing PhD degree at National Institute of Pharmaceutical education and research, Hyderabad, India. She is working on unraveling the ER stress mechanisms behind pathogenesis of diabetic neuropathy.

Anil Kumar Kalvala

Anil Kalvala is currently a post-doctoral researcher at University College of Pharmacy, Pharmaceutical Sciences, Florida A&M University, Tallahassee, Florida, USA. His research is focused on molecular mechanisms of mitochondrial dysfunction in neuropathic pain.

Bhoomika Sherkhane

Bhoomika Sherkhane is pursuing PhD degree at National Institute of Pharmaceutical education and research, Hyderabad, India. She is working on mitochondrial mechanisms including mitochondrial quality control systems underlying pathogenesis of diabetic kidney disease.

Dharmendra Kumar Khatri

Dr. Dharmendra Kumar Khatri is currently working as faculty in the Department of Pharmacology and Toxicology at National Institute of Pharmaceutical Education & Research-Hyderabad. His research is focused in a multidisciplinary approach to investigate the cellular and molecular mechanism underlying pathogenic degeneration of specific neuronal population in the Parkinson Disease brain. He is more like behavior pharmacologist. He works on a broad NeuroScience portfolio to support the industries on existing products and especially focus on new innovative drug in development for the treatment of brain disorder. Based on his scientific contribution in the neuroscience field he has been awarded with many prestigious fellowships and awards at national and international level.

Shashi Bala Singh

Dr. Shashi Bala Singh is currently working as the Director, NIPER Hyderabad. Prior to this, she was Distinguished Scientist and Director General (Life Sciences) at DRDO HQs, New Delhi. She has the distinction of serving as the Director of Defence Institute of High Altitude Research (DIHAR), Leh and Director, Defence Institute of Physiology and Allied Sciences (DIPAS) Delhi. She is an alumnus of All India Institute of Medical Sciences (AIIMS) where she obtained her MSc and Ph.D. degree in Human Physiology with Dr. B. K. Anand Gold Medal for best graduating student. She obtained her D.Sc. from Bharathiar University, Coimbatore. She has been instrumental in guiding studies on understanding adaptation, maladaptation, performance enhancement and rapid acclimatization using intermittent hypoxia and worked extensively in the area of High Altitude physiology and has made remarkable contributions in improving the quality of life of the soldiers deployed at high altitudes. She has identified novel mechanisms of hypophagia and cognitive impairment and several signaling pathways and molecular mechanisms underlying morbidities associated with high altitude hypoxia.