Diabetic neuropathy (DN) is a serious microvascular complication of
diabetes mellitus (DM) that impacts the nervous system. Several risk factors are involved in the progression and maintenance of DN-associated
pain, such as higher expression of various inflammatory mediators, e.g.,
tumor necrotic factor-alpha (TNF-α),
nuclear factor-kappa B (NF-κB), and cyclo-oxygenase-2 (COX-2). The present research explores the neuroprotective potential of natural isolates, including
berbamine,
bergapten, and
carveol, on the DM-induced
neuroinflammation and neurodegeneration that cause
neuropathic pain. The study utilized computerized techniques, including computational analysis (a docking assay and a molecular dynamic simulation) before moving to in vivo protocols.
Diabetic neuropathy was induced by intraperitonial injection (IP) of
streptozotocin (65 mg/kg), and the animal subjects (rats) were kept for 4 weeks for the development of DN. Once
diabetic neuropathy was confirmed, the subjects were treated with
berbamine,
bergapten, and
carveol until the sixth week (i.e., 2 weeks of treatment). At the sixth week, the rats were sacrificed, and the sciatic nerve and spinal cord of each was collected for further molecular investigation. Docking and a molecular dynamic simulation (MDS) delivered the information that the natural compounds (
berbamine,
bergapten, and
carveol) were interacting with the selected target
protein (i.e.,
mitogen-activated protein kinase). After IP, it was found that
berbamine,
bergapten, and
carveol had ameliorated
mechanical allodynia and
thermal hyperalgesia by the 28th day of the study (2 weeks
after treatment) without affecting
blood glucose levels.
Berbamine,
bergapten, and
carveol markedly elevated the levels of
glutathione (GSH) and
glutathione s-transferase (GST), in both the sciatic nerve and spinal cord, and also reduced
lipid peroxidase (LPO) and
nitric oxide (NO). The abovementioned natural isolates reduced pathologic alterations provoked through DN, a finding confirmed through histopathological assays (
hematoxylin and
eosin staining and immuno-histochemical analysis). Treatment down regulated higher expressions of the inflammatory mediatorcyclooxygenase-2 (COX-2),
tumor necrosis factor-α (TNF-α), and
nuclear factor kappa B (NF-κB), as confirmed by ELISA and polymerase chain reaction (PCR). The outcomes of
berbamine,
bergapten, and
carveol are compared with those of
pregabalin as a positive control group. Compared to
pregabalin, treatment with the aforementioned three natural compounds improved nociception and reduced hyperalgesic effects, and consequently reduced pain perception and
inflammation. Our results suggest the mechanism for the neuro-protective impact of
berbamine,
bergapten, and
carveol might possibly be arbitrated via COX-2, TNF-α, and NF-κB, and regulated by
mitogen-activated protein kinase, ultimately ameliorating STZ-provoked, DM-induced
neuroinflammation and neurodegeneration, and associated
neuropathic pain.