Background and Purpose:
Hemorrhage-caused gene changes in the thalamus likely contribute to thalamic pain genesis. RNA N
6
-methyladenosine modification is an additional layer of gene regulation. Whether FTO (fat-mass and obesity-associated protein), an N
6
-methyladenosine demethylase, participates in hemorrhage-induced thalamic pain is unknown.
Methods:
Expression of
Fto
mRNA and protein was assessed in mouse thalamus after hemorrhage caused by microinjection of Coll IV (type IV collagenase) into unilateral thalamus. Effect of intraperitoneal administration of meclofenamic acid (a FTO inhibitor) or microinjection of adeno-associated virus 5 (AAV5) expressing Cre into the thalamus of
Fto
fl/fl
mice on the Coll IV microinjection–induced TLR4 (Toll-like receptor 4) upregulation and nociceptive hypersensitivity was examined. Effect of thalamic microinjection of AAV5 expressing
Fto
(AAV5-
Fto
) on basal thalamic TLR4 expression and nociceptive thresholds was also analyzed. Additionally, level of N
6
-methyladenosine in
Tlr4
mRNA and its binding to FTO or YTHDF2 (YTH N
6
-methyladenosine RNA binding protein 2) were observed.
Results:
FTO was detected in neuronal nuclei of thalamus. Level of FTO protein, but not mRNA, was time-dependently increased in the ipsilateral thalamus on days 1 to 14 after Coll IV microinjection. Intraperitoneal injection of meclofenamic acid or adeno-associated virus-5 expressing Cre microinjection into
Fto
fl/fl
mouse thalamus attenuated the Coll IV microinjection–induced TLR4 upregulation and tissue damage in the ipsilateral thalamus and development and maintenance of nociceptive hypersensitivities on the contralateral side. Thalamic microinjection of AAV5-
Fto
increased TLR4 expression and elicited hypersensitivities to mechanical, heat and cold stimuli. Mechanistically, Coll IV microinjection produced an increase in FTO binding to
Tlr4
mRNA, an FTO-dependent loss of N
6
-methyladenosine sites in
Tlr4
mRNA and a reduction in the binding of YTHDF2 to
Tlr4
mRNA in the ipsilateral thalamus.
Conclusions:
Our findings suggest that FTO participates in hemorrhage-induced thalamic pain by stabilizing TLR4 upregulation in thalamic neurons. FTO may be a potential target for the treatment of this disorder.
Thalamic Pain Misdiagnosed as Cervical Disc Herniation
