Gallium nitrate suppresses lupus in MRL/lpr mice

Gallium (Ga) nitrate, a drug which prevents a variety of experimental autoimmune diseases, was investigated in a murine model of systemic lupus erythematosus (SLE). In one experiment, female MRL/Mp lpr/lpr (MRL/lpr) mice were randomized into 2 groups of 6:1) vehicle (trisodium citrate) and 2) Ga. Subcutaneous injections began at 3 weeks of age and continued weekly until the mice were euthanized a week after the thirteenth injection. The loading dose of Ga (calculated as elemental Ga) was 45 mg/kg, followed by 15 mg/kg/week. In another experiment ( n = 18) with 3 males and 3 females per group, mice received 1) vehicle, 2) Ga × 1 (one 45 mg/kg dose), and 3) Ga × 13. In the experiment with 12 mice, axillary lymph nodes from Ga-treated mice were significantly smaller than those from vehicle-treated mice (91 ± 42 and 360 ± 358 mg respectively, mean ± SD), and spleens as well as lymph nodes from the former showed significantly less lymphoid infiltrate. In the experiment with 18 mice, prescapular lymph nodes weighed 312 ± 98, 217 ± 52, and 42 ± 34 mg, and spleens weighed 732 ± 492, 409 ± 164, and 192 ± 93 mg in the groups which received vehicle, Ga × 1, and Ga × 13 respectively. Control mice had significantly more lymphoid infiltrates in the lungs, spleen, and lymph nodes and, unlike Ga × 13 mice, exhibited glomerulitis and renal vasculitis. Within groups, females developed more severe disease than males. The Ga × 13 group had increased percentages of CD4-bearing and CD8-bearing lymphocytes in lymph nodes and increased CD4-bearing lymphocytes in the spleen, with an increased proliferative response to mitogen stimulation in vitro in lymph nodes, although not in the spleen. The Ga × 13 group also gained less weight and developed osteosclerosis. Although preliminary, our findings suggest that clinical trials with Ga in SLE are merited.