Histone deacetylases--a new target for suppression of cartilage degradation?

A randomized phase II trial of Arginine Butyrate with standard local therapy in refractory sickle cell leg ulcers

Sickle cell leg ulcers are often debilitating, refractory to healing, and prone to recurrence. Healing of leg ulcers was incidentally observed during dose-ranging trials of Arginine Butyrate in beta haemoglobinopathies. Here, a controlled Phase II trial was performed in sickle cell patients who had lower extremity ulcers refractory to standard care for at least 6 months. Patients were randomized to receive standard local care alone (Control Arm) or standard care with Arginine Butyrate administered 5 d/week (Treatment Arm), for 12 weeks. Ulcers were photographed weekly, traced, and ulcer areas were calculated by computerized planimetry and compared between the two study arms. Twenty-seven study courses were evaluated. Control Arm subjects had 25 ulcers with a mean area of 25·7 cm(2) initially and 23·2 cm(2) after 12 weeks; 2/25 (8%) healed completely. Treatment Arm subjects had 37 ulcers with a mean area of 50·6 cm(2) initially and 28·3 cm(2) at 12 weeks; 11/37 of these (30%) healed completely. After 3 months, proportions of ulcers which healed were 6/25 (24%) and 29/37 (78%), in the Control and Treatment Arms respectively (P < 0·001). These findings strongly suggest that Arginine Butyrate merits further evaluation for the treatment of refractory sickle cell leg ulcers in larger trials.

Regulation of type II collagen expression by histone deacetylase in articular chondrocytes

Histone deacetylase (HDAC) regulates various cellular processes by modulating gene expression. Here, we investigated the role of HDAC in the expression of type II collagen, a marker of differentiated chondrocytes. We found that HDAC activity in primary articular chondrocytes decreases during dedifferentiation induced by serial monolayer culture and that the activity recovered during redifferentiation induced by three-dimensional culture in a cell pellet. Inhibition of HDAC with trichostatin A or PXD101 was sufficient to block type II collagen expression in primary culture chondrocytes. HDAC inhibition also blocked the redifferentiation of dedifferentiated chondrocytes by suppressing the synthesis and accumulation of type II collagen. HDAC inhibition promoted the expression of Wnt-5a, which is known to inhibit type II collagen expression, and knockdown of Wnt-5a blocked the ability of HDAC inhibitors to suppress type II collagen expression. In addition, the induction of Wnt-5a expression by HDAC inhibitors was associated with acetylation of the Wnt-5a promoter. Taken together, our results suggest that HDAC promotes type II collagen expression by suppressing the transcription of Wnt-5a.

Anti-rheumatic activities of histone deacetylase (HDAC) inhibitors in vivo in collagen-induced arthritis in rodents

BACKGROUND AND PURPOSE

Rheumatoid arthritis (RA) is a chronic inflammatory disease. Histone deacetylase inhibitors (HDACi), a new class of anti-cancer agents, have recently been reported to exhibit potent anti-inflammatory activities. A proof of concept study was carried out with suberoylanilide hydroxamic acid (SAHA) and MS-275, two HDACi currently undergoing clinical investigations for various oncological indications.

EXPERIMENTAL APPROACH

The anti-rheumatic effects of SAHA and MS-275 were assessed in both mouse and rat collagen induced arthritis (CIA) models.

KEY RESULTS

SAHA exhibited moderate prophylactic efficacy. It attenuated paw swelling due to inflammation, decreased bone erosion in both mice and rats and reduced slightly the RA-induced bone resorption in rats. However, SAHA could not inhibit the onset of arthritis. In contrast, MS-275 displayed dramatic anti-rheumatic activities. In prophylactic intervention, high doses of MS-275 prevented bone erosion and markedly delayed the onset of arthritis; at low doses, MS-275 strongly attenuated paw swelling, bone erosion, and bone resorption associated with RA. Furthermore, the therapeutic efficacy of MS-275 was also documented. After the onset of arthritis, it could stop the disease progression and joint destruction. An anti inflammatory effect of MS-275 was also confirmed through its capacity to decrease serum IL-6 and IL-1beta levels in the CIA induced mouse model. The anti-rheumatic activity of MS-275 was also confirmed through histological observation. No synovial hyperplasia, pannus formation, cartilage or bone destruction were observed in the high dose prophylactic intervention in mice.

CONCLUSION AND IMPLICATION

This study strongly supported HDACi as an innovative therapeutic strategy for RA.