Interactions between Autophagy, Proinflammatory Cytokines, and Apoptosis in Neuropathic Pain: Granulocyte Colony Stimulating Factor as a Multipotent Therapy in Rats with Chronic Constriction Injury

Abstract

Our previous studies have shown that early systemic granulocyte colony-stimulating factor (G-CSF) treatment can attenuate neuropathic pain in rats with chronic constriction injury (CCI) by modulating expression of different proinflammatory cytokines, microRNAs, and proteins. Besides the modulation of inflammatory mediators’ expression, previous studies have also reported that G-CSF can modulate autophagic and apoptotic activity. Furthermore, both autophagy and apoptosis play important roles in chronic pain modulation. In this study, we evaluated the temporal interactions of autophagy, and apoptosis in the dorsal root ganglion (DRG) and injured sciatic nerve after G-CSF treatment in CCI rats. We studied the behaviors of CCI rats with or without G-CSF treatment and the various levels of autophagic, proinflammatory, and apoptotic proteins in injured sciatic nerves and DRG neurons at different time points using Western blot analysis and immunohistochemical methods. The results showed that G-CSF treatment upregulated autophagic protein expression in the early phase and suppressed apoptotic protein expression in the late phase after nerve injury. Thus, medication such as G-CSF can modulate autophagy, apoptosis, and different proinflammatory proteins in the injured sciatic nerve and DRG neurons, which have the potential to treat neuropathic pain. However, autophagy-mediated regulation of neuropathic pain is a time-dependent process. An increase in autophagic activity in the early phase before proinflammatory cytokines reach the threshold level to induce neuropathic pain can effectively alleviate further neuropathic pain development.

The Role of Autophagy and Apoptosis in Neuropathic Pain Formation

“…There are three types of autophagy: macroautophagy, microautophagy, and chaperone-mediated autophagy (CMA) [ 6 , 8 ]. Different animal pain models have demonstrated alterations in macroautophagic activities in the injured nerve, dorsal root ganglia [ 23 , 24 , 25 , 26 , 27 , 28 , 29 ], spinal cord [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ], and brain [ 43 ] after peripheral nerve damage. At the beginning of the macroautophagic process, Beclin-1 and Ambra1 (both are the upper stream proteins of the macroautophagy process) at the endoplasmic reticulum respond to the stress signaling pathway and initiate phagophore formation.…”

“…LAMP2A expressions increased on the sciatic nerve of rats with chronic inflammatory demyelinating polyneuropathy (CIDP) [ 60 ]. Many studies focused on macroautophagy changes in the neurons of animals after nerve damage with rapamycin or 3-MA treatment [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. Most studies proposed that when macroautophagic activities increase, the expression levels of LC3-II, Bclin-1, and Atg5-Atg12 increase, but p62 levels (delivering ubiquitinated cargoes to autophagosomes) decrease [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ].…”

“…Many studies focused on macroautophagy changes in the neurons of animals after nerve damage with rapamycin or 3-MA treatment [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. Most studies proposed that when macroautophagic activities increase, the expression levels of LC3-II, Bclin-1, and Atg5-Atg12 increase, but p62 levels (delivering ubiquitinated cargoes to autophagosomes) decrease [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. However, some authors stated that, lately, increased LC3-II expressions indicate that the autophagic flux is blocked and autophagic activities are decreased [ 35 ].…”

“…However, there is no direct evidence that inhibition of apoptotic activities in the injured neurons can attenuate pain behavior. In contrast to apoptosis, many studies with different animal models have shown changed autophagic activities in the injured nerve [ 23 , 24 , 25 , 26 , 27 , 28 , 29 ], spinal cord [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ], and even brain [ 43 ] after nerve injury. These studies also showed that upregulated autophagic activities can directly alleviate neuropathic pain [ 24 , 26 , 27 , 32 , 33 , 37 , 38 ].…”

Potamogeton perfoliatus L. Extract Attenuates Neuroinflammation and Neuropathic Pain in Sciatic Nerve Chronic Constriction Injury-Induced Peripheral Neuropathy in Rats

“…Apoptosis and oxidative stress play a role in the onset and progression of neuropathic pain (Areti et al, 2014). Apoptotic changes in the spinal cord following CCI is well documented (Giardini et al, 2017;Liao et al, 2021). In our study, we assessed the apoptotic changes of the sciatic nerve and the neurons of brainstem 14 days after CCI.…”