RhoB blockade selectively inhibits autoantibody production in autoimmune models of rheumatoid arthritis and lupus

During the development of autoimmune disease, a switch occurs in the antibody repertoire of B cells so that the production of pathogenic rather than non-pathogenic autoantibodies is enabled. However, there is limited knowledge concerning how this pivotal step occurs. Here, we present genetic and pharmacological evidence of a positive modifier function for the vesicular small GTPase RhoB in specifically mediating the generation of pathogenic autoantibodies and disease progression in the K/BxN preclinical mouse model of inflammatory arthritis. Genetic deletion of RhoB abolished the production of pathogenic autoantibodies and ablated joint inflammation in the model. Similarly, administration of a novel RhoB-targeted monoclonal antibody was sufficient to ablate autoantibody production and joint inflammation. In the MRL/lpr mouse model of systemic lupus erythematosus (SLE), another established preclinical model of autoimmune disease associated with autoantibody production, administration of the anti-RhoB antibody also reduced serum levels of anti-dsDNA antibodies. Notably, the therapeutic effects of RhoB blockade reflected a selective deficiency in response to self-antigens, insofar as RhoB-deficient mice and mice treated with anti-RhoB immunoglobulin (Ig) both mounted comparable productive antibody responses after immunization with a model foreign antigen. Overall, our results highlight a newly identified function for RhoB in supporting the specific production of pathogenic autoantibodies, and offer a preclinical proof of concept for use of anti-RhoB Ig as a disease-selective therapy to treat autoimmune disorders driven by pathogenic autoantibodies

Meglumine Exerts Protective Effects against Features of Metabolic Syndrome and Type II Diabetes

<div><p>Metabolic syndrome, diabetes and diabetes complications pose a growing medical challenge worldwide, accentuating the need of safe and effective strategies for their clinical management. Here we present preclinical evidence that the sorbitol derivative meglumine (N-methyl-D-glucamine) can safely protect against several features of metabolic syndrome and diabetes, as well as elicit enhancement in muscle stamina. Meglumine is a compound routinely used as an approved excipient to improve drug absorption that has not been ascribed any direct biological effects <i>in vivo</i>. Normal mice (SV129) administered 18 mM meglumine orally for six weeks did not display any gastrointestinal or other observable adverse effects, but had a marked effect on enhancing muscle stamina and at longer times in limiting weight gain. In the established KK.Cg-Ay/J model of non-insulin dependent diabetes, oral administration of meglumine significantly improved glycemic control and significantly lowered levels of plasma and liver triglycerides. Compared to untreated control animals, meglumine reduced apparent diabetic nephropathy. Sorbitol can improve blood glucose uptake by liver and muscle in a manner associated with upregulation of the AMPK-related enzyme SNARK, but with undesirable gastrointestinal side effects not seen with meglumine. In murine myoblasts, we found that meglumine increased steady-state SNARK levels in a dose-dependent manner more potently than sorbitol. Taken together, these findings provide support for the clinical evaluation of meglumine as a low-cost, safe supplement offering the potential to improve muscle function, limit metabolic syndrome and reduce diabetic complications.</p></div

Meglumine reduces hyperglycemia.

<p>The figure presents the proportion of hyperglycemic mice that survived to the experimental endpoint of 7 months after receiving drinking water that was either untreated (<b>left bar</b>) or treated with meglumine (<b>right bar</b>).</p

Serum and liver triglycerides are lowered by meglumine treatment.

<p>Seven month old KK.Cg-Ay/J mice were analyzed in this experiment having received drinking water that was untreated or treated with meglumine. A<b>:</b> Serum triglyceride levels. In untreated mice, levels were ∼750–800 mg/dL (<b>left bar, white</b>) whereas meglumine-treated mice displayed significantly lower levels of ∼300 mg/dL (<b>right bar, black</b>). Values are mean ± SE shown in the error bar. n = 10 for both groups. P = 0.00007. B<b>:</b> Liver triglyceride levels. Values are mean ± SE shown in the error bar. Water group, n = 10; meglumine group, n = 9. P = 0.043.</p

Meglumine increases SNARK levels in myoblasts.

<p>Panels show the results of Western analyses of total protein isolated from C2C12 murine myoblasts treated with meglumine, sorbitol or glucosamine at various concentrations and times. Actin levels were used as a control for equal protein loading in the gel lanes. A: Cells were treated with varying amounts of meglumine for 60 minutes (left side) or 200 mM meglumine for varying times (right side). B: Myoblasts were treated with various levels of meglumine or sorbitol for 30 min (left panel) or with 200 mM meglumine or sorbitol for various times (right panel). C: Cells were treated with varying amounts of meglumine or sorbitol for 60 minutes before analysis of the levels of SNARK or total or phospho-specific levels of its substrate MYPT1 phosphorylated at Ser507, Ser668 or Thr696. D: Cells were treated with varying amounts of meglumine or glucosamine for 60 minutes before analysis of SNARK levels.</p

Trend in amelioration of nephropathy by meglumine in female diabetic mice.

<p>Kidney sections obtained from KK.Cg-Ay/J mice treated with or without meglumine in their drinking water for seven months were examined blindly by a kidney pathologist for evidence of nephritis, hydronephrosis, atrophy-fibrosis, glomerulosclerosis and tubular dilation. Severity was ranked qualitatively using a 0–4 scale where 0 = normal and 4 = severe lesion. The values presented in the Table represent the mean ± SE using this scale. Females in this model exhibit more nephropathy than males, the latter of which did not exhibit the beneficial trend seen in females. ♂, male; ♀, female; n, number of mice examined.</p

Kidney weight in diabetic animals is reduced by meglumine treatment.

<p>Kidney weights were measured postmortem in KK.Cg-Ay/J mice euthanized 7 months after initiation of the experiment. Untreated mice display higher kidney weights averaging ∼290 mg (<b>left bar, white</b>) whereas meglumine-treated mice display lower kidney weights averaging ∼260 mg (<b>right bar, black</b>). Values are mean ± SE shown in the error bar. n = 20 in both groups. P = 0.017.</p

Meglumine reduces fasting blood glucose levels.

<p>KK.Cg-Ay/J mice treated with meglumine exhibited better glucose control and overall lower glucose levels than untreated mice. Most untreated hyperglycemic mice died between 3–7 months of age. Values are mean ± SE shown in the error bar. n = 20 for both groups (although not all time-points included measurements from all animals in each group). Asterisk designates P<0.05.</p