preproenkephalin and Arthritis

Rheumatoid arthritis is characterized by erosive inflammation of the joints, new bone proliferation, and ankylosis, leading to severely reduced locomotion and intense chronic pain. In a model of this disease, adjuvant-induced polyarthritis in the rat, neurons involved in pain transmission and control undergo plastic changes, especially at the spinal level. These changes affect notably neurons that contain opioids, such as enkephalins deriving from preproenkephalin A (PA) precursor protein. Using recombinant herpes simplex virus containing rat PA cDNA, we enhanced enkephalin synthesis in sensory neurons of polyarthritic rats. This treatment markedly improved locomotion and reduced hyperalgesia. Furthermore, the progression of bone destruction slowed down, which is the most difficult target to reach in the treatment of patients suffering from arthritis. These data demonstrate the therapeutic efficacy of enkephalin overproduction in a model of systemic inflammatory and painful chronic disorder.

Topics: Animals; Arthritis; Arthritis, Experimental; Disease Models, Animal; Disease Progression; Enkephalins; Freund's Adjuvant; Ganglia, Spinal; Genes, Reporter; Genetic Therapy; Genetic Vectors; Herpesvirus 1, Human; Hindlimb; Hyperalgesia; Male; Neurons, Afferent; Pain Measurement; Protein Precursors; Rats; Rats, Sprague-Dawley; Severity of Illness Index; Terminal Repeat Sequences; Treatment Outcome

Changes in the spinal expression of the opioid precursor and prodynorphin, which has been implicated in the response to peripheral inflammation, were examined with semi-quantitative in situ hybridization histochemistry in rats subjected to collagen II-induced arthritis. The effects of glucocorticosteroid treatment on the basal and inflammation-induced prodynorphin expression were evaluated. Collagen II-induced arthritis caused a 16-fold increase in prodynorphin mRNA levels which comprised all neurons expressing low levels under normal conditions. In the superficial dorsal horn, one group of neurons of a large size reacted with a dramatic increase of prodynorphin mRNA, while another group of small neurons exhibited a moderate elevation of prodynorphin mRNA levels. In the deep dorsal horn of arthritic rats, most prodynorphin neurons were large and showed high prodynorphin mRNA levels. Systemic treatment with the glucocorticosteroid budesonide attenuated the arthritis-induced increase of prodynorphin mRNA expression in a topospecific manner. The budesonide-induced reduction of prodynorphin mRNA levels was more pronounced in the deep dorsal horn than in the superficial dorsal horn. Budesonide treatment of control animals caused a small, but significant increase in prodynorphin mRNA levels in the superficial laminae I/II without affecting prodynorphin mRNA levels in the deep dorsal horn. The degree of arthritis correlated closely with spinal prodynorphin mRNA levels. The tight correlation between severity of arthritis and prodynorphin mRNA levels in non-treated and corticosteroid-treated arthritic rats suggests that spinal prodynorphin expression is a good parameter for the evaluation of the influence of peripheral inflammation and of the efficacy of analgesic/anti-inflammatory drugs in its treatment. Opposite effects of budesonide on basal and inflammation-induced prodynorphin expression may involve a spinal site of action in addition to peripheral anti-inflammatory mechanisms. We suggest that the collagen II-induced arthritis in the rat is an excellent model for human rheumatoid arthritis allowing for the study of molecular plasticity of anti-inflammatory and anti-nociceptive drug action at different levels of the neuroaxis.

Topics: Administration, Topical; Animals; Anti-Inflammatory Agents; Arthritis; Budesonide; Collagen; DNA Probes; Enkephalins; Female; Gene Expression; Glucocorticoids; Hindlimb; Image Processing, Computer-Assisted; In Situ Hybridization; Pregnenediones; Protein Precursors; Rats; RNA, Messenger; Spinal Cord; Up-Regulation

The response of dynorphinergic neurons in the lumbosacral spinal cord of the rat to chronic arthritic inflammation was studied by the combined use of biochemical and immunohistochemical procedures. In polyarthritic rats, in which all four limbs showed a swelling, inflammation and hyperalgesia, a pronounced elevation was seen in the level of messenger ribonucleic acid encoding prodynorphin (pro-enkephalin B) in the lumbosacral spinal cord. In addition, the levels of immunoreactive dynorphin A1-17, a primary gene product of this precursor, were greatly increased. This activation was reflected in a striking intensification of the immunohistochemical staining of both dynorphin and alpha/beta-neo-endorphin, a further major product of pro-dynorphin. In control animals perikarya were stained exceedingly rarely and encountered only in laminae I and II. Stained fibres and varicosities were seen throughout the dorsal and ventral gray matter, being most concentrated in laminae I, II, IV and V of the dorsal horn and dorsolateral to the central canal. In polyarthritic rats, fibres and varicosities were much more intensely stained throughout the cord, particularly in laminae I/II, IV and V and dorsolateral to the central canal. Many strongly-stained perikarya could be seen: these comprised many small diameter cells in laminae I and II, and some large diameter marginal neurons and large diameter cells, heterogenous in appearance, in the deeper laminae IV and V. Monolaterally inflamed rats injected in the right hind-paw showed pathological changes only in this limb. Correspondingly, in unilateral inflammation, an elevation in immunoreactive dynorphin was seen exclusively in the right dorsal horn and the above-described intensification of staining for dynorphin and neo-endorphin was seen only in this quadrant. This reveals the neuroanatomical specificity of the response. Thus, in the lumbosacral cord of the rat, pro-dynorphin neurons are most preponderant in laminae I, II, IV and V. A pronounced intensification of the immunohistochemical staining of these neurons is seen in chronic arthritis. Furthermore, there is a parallel elevation in the levels of messenger ribonucleic acid encoding pro-dynorphin and of its primary products dynorphin and neo-endorphin. These findings demonstrate an enhancement in the functional activity of spinal cord localized dynorphin neurons in the response to chronic arthritic inflammation.

Topics: Animals; Arthritis; Dynorphins; Enkephalins; Gene Expression Regulation; Immunohistochemistry; Male; Pain; Protein Precursors; Rats; Rats, Inbred Strains; RNA, Messenger; Spinal Cord

The influence of adjuvant-induced arthritis of the rat on central and peripheral peptide neuroanatomy was investigated by immunohistochemistry. The most striking feature of arthritic rats was the differential intensification of neuronal proenkephalin- and prodynorphin-related staining in dorsal horn. Changes were ipsilateral in monoarthritic and bilateral in polyarthritic rats as compared to controls. Opioid responsive neurons were target of substance P (SP) and calcitonin gene-related peptide (CGRP) fibers. Changes of SP and CGRP predominated in peripheral inflamed tissue and consisted of intensified immunostaining and an apparent sprouting of sensory fibers particularly around venules, in the epidermis and in areas infiltrated by immunocompetent cells. Opioid staining was absent from primary afferents but present in some immune cells of inflamed tissue. Endogenous antinociceptive opioids and pro-nociceptive/pro-inflammatory SP and CGRP may be crucial in the concerted response of the neuroimmune system to chronic inflammatory pain.

Topics: Animals; Arthritis; Arthritis, Experimental; Calcitonin Gene-Related Peptide; Enkephalins; Ganglia, Spinal; Immunohistochemistry; Nerve Fibers; Neuropeptides; Protein Precursors; Rats; Rats, Inbred Strains; Skin; Spinal Cord; Substance P

The influence of chronic arthritic pain upon the levels of mRNA encoding prodynorphin (mRNADYN) in the spinal cord of rats was evaluated by use of the RNA blot technique. Rats were rendered arthritic by inoculation of the tail-base with a suspension of Mycobacterium butyricum. Three weeks post inoculation, levels of mRNADYN revealed a pronounced alteration in arthritic rats by a factor of greater than or equal to 2.5 as compared to control animals. This rise was specific in that there was no change in total RNA content. These data indicate that the biosynthetic activity of the dynorphin system is facilitated under chronic pain. Together with our previous biochemical and behavioural data, a functional role of this system in the response to chronic pain is suggested.

Topics: Animals; Arthritis; Arthritis, Experimental; Body Weight; Enkephalins; Gene Expression Regulation; Male; Nucleic Acid Hybridization; Organ Size; Pain; Protein Precursors; Rats; Rats, Inbred Strains; RNA; RNA, Messenger; Spinal Cord