Mechanisms of bee venom-induced acute renal failure

A novel analog of antimicrobial peptide Polybia-MPI, with thioamide bond substitution, exhibits increased therapeutic efficacy against cancer and diminished toxicity in mice

Polybia-MPI (MPI), a short cationic α-helical antimicrobial peptide, exhibited excellent anticancer activity and selectivity in vitro in our previous studies. To improve its in vivo application, we synthesized an analog (MPI-1) of MPI by replacing the C terminal amide -[CO-NH(2)] with thioamide -ψ[CS-NH(2)]. Although there is just one atom difference, the MPI-1 exhibited some surprising properties. In vitro studies revealed that MPI-1 exhibited relatively high lytic activity over MPI, whereas its stability to enzymatic degradation in serum was improved remarkably. Despite the enhanced toxicity in vitro, MPI-1 exhibited significantly lower mortality to mice than MPI at 75 mg/kg. Importantly, in vivo anticancer activity study indicated that MPI-1 could remarkably suppress the growth of sarcoma xenograft tumors more efficiently than MPI. Therefore, the significantly improved anticancer activity and predominantly lower in vivo toxicity might allow MPI-1 to be a good candidate for future anticancer treatment.

Acute physiopathological effects of honeybee (Apis mellifera) envenoming by subcutaneous route in a mouse model

Bee stings are a health concern in the Americas, where fatal envenomings due to massive attacks by Africanized honeybees have been documented in the last decades. Most studies on the toxic effects of honeybee venom in experimental animals have been performed using the intravenous or intraperitoneal injection routes. The aim of this study was to develop a mouse model that would better resemble a massive honeybee attack by using the subcutaneous (s.c.) route to induce a severe, sublethal systemic envenoming. An array of acute venom effects were characterized, including biochemical, hematological, histological, and inflammatory alterations, after the s.c. injection of 0.5 median lethal dose of venom. Rapid increases in serum alanine (ALT) and aspartate (AST) transaminases, creatinine, urea nitrogen, uric acid, sodium and chloride electrolytes, and creatine kinase (CK) were recorded, indicating damage to liver, kidneys, and skeletal muscle. Also, coagulation disturbances (fibrinogen decrease, and moderate delay in prothrombin and partial thromboplastin times) were demonstrated. Circulating platelet and leukocyte numbers remained unaltered, but a hemoconcentration effect (hematocrit and hemoglobin increase) was observed. This effect might be related to the marked edema induced by the venom. In addition, this inflammatory response included a systemic increase in cytokines (IL-1 beta, IL-6, TNF-alpha), together with an elevation of serum malondialdehyde and nitric oxide. The myotoxic effects of venom, melittin, and phospholipase A(2) were demonstrated after injection by s.c. route. No synergistic myotoxicity between melittin and PLA(2) was observed. Moreover, these two components, when injected at equivalent concentrations to those present in venom, induced a lower increase in serum CK than venom, suggesting that other components also contribute to its strong systemic toxicity towards skeletal muscle. The model here presented may be useful in preclinical studies to assess therapeutic antivenoms developed to cope with the problem of massive bee attacks.

Honeybee venom induces calcium-dependent but caspase-independent apoptotic cell death in human melanoma A2058 cells

Honeybee (Apis mellifera) venom (BV) has been reported to exhibit anticancer effects, but its mode of action at the cellular and molecular levels remains largely unknown. We found that honeybee venom induced apoptosis in human melanoma A2058 cells but not in normal skin fibroblast Detroit 551 cells. The BV-induced apoptosis was accompanied by generation of reactive oxygen species and alteration of mitochondrial membrane potential transition. Treatment with antioxidants significantly attenuated BV-induced apoptosis. Although caspase-2 and -3 were slightly activated by BV, inhibitors of caspase-2 and -3 could not block BV-induced apoptosis in A2058 cells. Data from immunostaining indicated that EndoG and AIF were translocated from mitochondria to the cytosol or nucleus, suggesting that BV induces apoptosis in A2058 cells via a caspase-independent pathway. In addition, cJun N-terminal kinases (JNK) and ERK were rapidly activated after a 5 min incubation with BV, while p38 and AKT were inactivated after 30 min administration of BV. Inhibition of JNK significantly attenuated BV-triggered apoptotic death. Moreover, BV induced a rapid and marked increase in cytosolic calcium ion. Incubation of cells under calcium-free conditions effectively diminished BV-induced apoptosis. Furthermore, when the calcium-free treatment was combined with ouabain, the recovery of cellular calcium fluctuation protected A2058 cells against BV-induced apoptosis. Finally, treatment of A2058 cells with melittin, the major component of BV, resulted in similar elevation of calcium levels and cell killing effects, suggesting that melittin is the major determinant in BV-triggered cell death. These observations provide a molecular explanation for the antiproliferative properties of BV, and suggest that this agent may be useful in treating melanoma.

Pathological findings in dogs after multiple Africanized bee stings

This retrospective study included 19 dogs that died by intoxication due to multiple Africanized bee stings. Bee accidents occurred in rural and urban areas of the Rio Grande do Sul state, southern Brazil. Although bee stings were associated with edema and hyperemia in several regions of the body, head and neck were the most commonly and massively affected areas. Stingers and bees were also observed in the digestive tract. Dark-colored kidneys, dark-red urine, splenomegaly, and dark red lungs were the main gross changes. Histologically, all the dogs had kidney tubular degeneration and necrosis, which were associated with tubular pigment accumulation in most cases. Other lesions included muscular necrosis, hemorrhage in different organs, marked congestion of the spleen and pulmonary edema and congestion.