Many cancerous solid tumors metastasize to the bone and induce pain (cancer-induced bone pain [CIBP]). Cancer-induced bone pain is often severe because of enhanced inflammation, rapid bone degradation, and disease progression. Opioids are prescribed to manage this pain, but they may enhance bone loss and increase tumor proliferation, further compromising patient quality of life. Angiotensin-(1-7) (Ang-(1-7)) binds and activates the Mas receptor (MasR). Angiotensin-(1-7)/MasR activation modulates inflammatory signaling after acute tissue insult, yet no studies have investigated whether Ang-(1-7)/MasR play a role in CIBP. We hypothesized that Ang-(1-7) inhibits CIBP by targeting MasR in a murine model of breast CIBP. 66.1 breast cancer cells were implanted into the femur of BALB/cAnNHsd mice as a model of CIBP. Spontaneous and evoked pain behaviors were assessed before and after acute and chronic administration of Ang-(1-7). Tissues were collected from animals for ex vivo analyses of MasR expression, tumor burden, and bone integrity. Cancer inoculation increased spontaneous pain behaviors by day 7 that were significantly reduced after a single injection of Ang-(1-7) and after sustained administration. Preadministration of A-779 a selective MasR antagonist prevented this reduction, whereas pretreatment with the AT(2) antagonist had no effect; an AT(1) antagonist enhanced the antinociceptive activity of Ang-(1-7) in CIBP. Repeated Ang-(1-7) administration did not significantly change tumor burden or bone remodeling. Data here suggest that Ang-(1-7)/MasR activation significantly attenuates CIBP, while lacking many side effects seen with opioids. Thus, Ang-(1-7) may be an alternative therapeutic strategy for the nearly 90% of patients with advanced-stage cancer who experience excruciating pain.

Denervation leads to skeletal muscle atrophy, which is a decrease in muscle mass and force; the latter exceeding expectation from mass loss. In some cases, nerve regeneration following an injury takes several months. During this time, muscle mass and force loss become severe as fibers are replaced by connective and fat tissue, which can further prolongs normal muscle function recovery once reinnervation occurs. The objectives of this study were 1) document the angiotensin 1-7 (Ang 1-7) hypertrophic effect in innervated mouse skeletal muscle; 2) test the hypothesis that Ang 1-7 prevents muscle atrophy and maintain force following short 2 and 4 week denervation; 3) as well as following long 16 week denervation. Innervated and denervated mice were treated with Ang 1-7 or diminazene aceturate (DIZE), an ACE2 activator, to increase plasma Ang 1-7 level. In normal innervated extensor digitorum longus (EDL) and soleus muscle, Ang 1-7 increased muscle weight, cross sectional area (CSA) and tetanic force, which represents the muscle maximum force. During the short denervation period (2-4 weeks), Ang 1-7 did not prevent muscle mass and CSA loss, but fully abolished the loss of normalized tetanic force to CSA while accentuating twitch force. Normalized tetanic force was maintained as Ang 1-7 partially reduced the extent of membrane depolarization which normally observed with denervation, and it fully prevented the loss of membrane excitability. The protective effect of Ang 1-7 on maximum tetanic force was also observed after 16 weeks of denervation, but only in EDL not in soleus. About 35-40% of denervated EDL and soleus muscle fibers became reinnervated over the 16 week period and Ang 1-7 enhanced the recovery of muscle mass and tetanic force in both EDL and soleus. All Ang 1-7 effects on twitch and tetanic force were completely blocked by A779, a Mas receptor (MasR) antagonist, and were not observed in MasR deficient (MasR / ) muscles. Ang 1-7 did not affect how denervation modulates changes in the protein content MuRF-1 atrogin-1, two atrophic proteins, total and phosphorylated Akt, S6K and 4EPB, three hypertrophic proteins. So, the Ang 1-7 effect involves an activation of its MasR, but it is not clear which intracellular pathway it then affects. This is the first study providing evidence that Ang 1-7 maintains normal muscle function in terms of tetanic force and membrane excitability during 2, 4 and 16 week denervation periods.