RNF13 protects against pathological cardiac hypertrophy through p62-NRF2 pathway.

Heart failure (HF) severely impairs human health because of its high incidence and mortality. Cardiac hypertrophy is the main cause of HF, while its underlying mechanism is not fully clear. As an E3 ubiquitin ligase, Ring finger protein 13 (RNF13) plays a crucial role in many disorders, such as liver immune, neurological disease and tumorigenesis, whereas the function of RNF13 in cardiac hypertrophy remains largely unknown. In the present study, we found that the protein expression of RNF13 is up-regulated in the transverse aortic constriction (TAC)-induced murine hypertrophic hearts and phenylephrine (PE)-induced cardiomyocyte hypertrophy. Functional investigations indicated that RNF13 global knockout mice accelerates the degree of TAC-induced cardiac hypertrophy, including cardiomyocyte enlargement, cardiac fibrosis and heart dysfunction. On the contrary, adeno-associated virus 9 (AAV9) mediated-RNF13 overexpression mice alleviated cardiac hypertrophy. Furthermore, we demonstrated that adenoviral RNF13 attenuates the PE-induced cardiomyocyte hypertrophy and down-regulates the expression of cardiac hypertrophic markers, while the opposite results were observed in the RNF13 knockdown group. The RNA-sequence of RNF13 knockout and wild type mice showed that RNF13 deficiency activates oxidative stress after TAC surgery. In terms of the mechanism, we found that RNF13 directly interacted with p62 and promoted the activation of downstream NRF2/HO-1 signaling. Finally, we proved that p62 knockdown can reverse the effect of RNF13 in cardiac hypertrophy. In conclusion, RNF13 protects against the cardiac hypertrophy via p62-NRF2 axis.

Role of GALNT4 in protecting against cardiac hypertrophy through ASK1 signaling pathway.

Pathological myocardial hypertrophy is regulated by multiple pathways. However, its underlying pathogenesis has not been fully explored. The goal of this work was to elucidate the function of polypeptide N-acetylgalactosaminyltransferase 4 (GALNT4) in myocardial hypertrophy and its underlying mechanism of action. We illustrated that GALNT4 was upregulated in the models of hypertrophy. Two cardiac hypertrophy models were established through partial transection of the aorta in GALNT4-knockout (GALNT4-KO) mice and adeno-associated virus 9-GALNT4 (AAV9-GALNT4) mice. The GALNT4-KO mice demonstrated accelerated cardiac hypertrophy, dysfunction, and fibrosis, whereas the opposite phenotype was observed in AAV9-GALNT4 mice. Similarly, GALNT4 overexpression mitigated the degree of phenylephrine-induced cardiomyocyte hypertrophy in vitro whereas GALNT4 knockdown aggravated the hypertrophy. In terms of mechanism, GALNT4 deficiency increased the phosphorylation and activation of ASK1 and its downstream targets (JNK and p38), whereas GALNT4 overexpression inhibited activation of the ASK1 pathway. Furthermore, we demonstrated that GALNT4 can directly bind to ASK1 inhibiting its N-terminally mediated dimerization and the subsequent phosphorylation of ASK1. Finally, an ASK1 inhibitor (iASK1) was able to reverse the effects of GALNT4 in vitro. In summary, GALNT4 may serve as a new regulatory factor and therapeutic target by blocking the activation of the ASK1 signaling cascade.

Plasmakinetic enucleation of the prostate vs plasmakinetic resection of the prostate for benign prostatic hyperplasia: comparison of outcomes according to prostate size in 310 patients.

OBJECTIVE: To compare the safety and efficiency of plasmakinetic enucleation of the prostate (PKEP) with that of plasmakinetic resection of the prostate (PKRP) in the treatment of benign prostatic hyperplasia (BPH). MATERIALS AND METHODS: Three hundred ten patients diagnosed to have BPH were randomized to undergo either PKEP or PKRP. The perioperative data and postoperative outcomes followed at 1, 3, 6, 12, 18, and 24 months after surgery were recorded and compared in the groups classified according to the baseline prostate volume: ≤ 60 mL and >60 mL. RESULTS: There were no significant differences in the preoperative data. Compared with PKRP, PKEP costs longer operative time (56.1 ± 14.6 vs 41.3 ± 9.6 min; P < .001) for prostate volume ≤ 60 mL, but reduced operative time (75.6 ± 12.3 vs 88.7 ± 14.3 minutes; P <.001) and caused less blood loss (167.6 ± 44.4 vs 225.7 ± 49.5 mL; P < .001) for prostate volume >60 mL. However, regardless of prostate size, the incidence of transient incontinence after PKEP was higher. The postoperative improvement among these groups in International Prostate Symptom Score, quality of life, and maximal flow rate was similar at 24-month follow-up. CONCLUSION: PKEP and PKRP are both safe and effective treatments for BPH independent of prostate size. Despite that the incidence of transient incontinence after PKEP was higher, PKEP was significantly superior to PKRP in operative time and blood loss for prostate volume >60 mL and may become the modern alternative to PKRP for large BPH.

[Protective effects of snake venom antimicrobial peptide OH-CATH on E. coli induced rabbit urinary tract infection models].

To investigate the potential protective effects of the snake venom antimicrobial peptide OH-CATH, we used a series of rabbit urinary tract infection models successfully induced by cephalosporin-resistant E.coli and E. coli ATCC 25922. The experimental models were administered saline, snake venom antimicrobial peptide OH-CATH, Cefoperazone and Sulbactam through the urethra. Urine was collected on days 1, 5, 10 and 14 after model establishment and urine culture was done to check the infection in each experimental animals. On day 14, all the animals were sacrificed and the bladder tissue specimens were taken for observation by H-E staining light microscope and transmission electron microscope. We found that the snake venom antimicrobial peptide OH-CATH reduced bacterial count in urine culture in both cephalosporin-resistant E. coli and the E. coli ATCC 25922 infected animals, while Cefoperazone and Sulbactam were only able to reduce the positive rate induced by the E. coli ATCC 25922 but had no obvious effects on animal model induced by cephalosporin-resistant E. coli strains (P<0.05). We also found less necrosis, degeneration and inflammatory cell infiltration in bladder tissue in OH-CATH groups as compared with the other experimental groups. The snake venom antimicrobial peptide OH-CATH had stable antibacterial activity against cephalosporin-resistant E. coli and E. coli ATCC 25922 and exhibited protective effects on both the cephalosporin-resistant E. coli and E. coli ATCC 25922 rabbit urinary tract infection models, suggesting that the molecule may have potential clinical applications in treating urinary tract infections.

Screening of differentially expressed genes in the jejunum of rats with idiopathic hyperoxaluria.

BACKGROUND: Idiopathic hyperoxaluria (IH) may be caused by increased endogenous formation or exogenous absorption of oxalic acid. Characterization of the molecular pathogenesis of IH has been hampered by the lack of an ideal animal model. We therefore established a stabile rat IH model in order to analyze variation in gene expression profile in the jejunum and to investigate the association between IH pathogenesis and exogenous absorption of oxalic acid. METHODS: A rat model of IH was established and three female rats with IH were assigned to the study group, while three normal rats served as controls. Total RNA was isolated from the jejunum of rats in the two groups and mRNA was purified, reversely transcribed, labeled with Cy5 or Cy3 and hybridized to 27K Rat Genome Array. Differences in gene expression profile between the 2 groups were analyzed by bioinformatics methods. RESULTS: Comparative analysis revealed that the expression of 517 genes was up-regulated and that of 203 genes was down-regulated by at least two-fold in the jejunum of rats with idiopathic hyperoxaluria. These genes are related to many functions including cell signal transduction, DNA binding and transcription, ATP binding, ion binding and transport, cell receptors, immunity, cyclins, cytoskeleton structure, and metabolic proteins. Kyoto encyclopedia of genes and genomes (KEGG) signaling pathway analysis revealed that the variations of 239 pathway functional changes are statistically significant (P < 0.05). CONCLUSIONS: cDNA microarray can be used effectively to screen differentially expressed genes in the jejunum of rats with idiopathic hyperoxaluria. These differentially expressed genes may underlie idiopathic hyperoxaluria pathophysiology and provide a platform for further studying molecular pathogenetic mechanisms.

Comparison of two different formulations of botulinum toxin A for the treatment of blepharospasm and hemifacial spasm.

AIM: To confirm and compare the therapeutic efficacies and adverse effects of Chinese botulinum toxin type A (CBTX-A, Lanzhou Biological Products Institute, China) and current Botox (Allergan Inc., CA, USA) in the treatment of blepharospasm (BS) and hemifacial spasm (HFS). MATERIAL AND METHODS: We performed an open, prospective, comparative trial comparing CBTX-A and Botox for the treatment of BS and HFS in 273 patients since 2006. 107 patients were treated with current Botox and 166 with CBTX-A, with the age, disease durations and severity of spasm matched. The patients enrolled were followed up for 6 months. RESULTS: There were no significant differences in the clinical effects of the two preparations, including the onset of response, peaked effect time and duration of effects (p > 0.05). The Cohen scores showed a significant reduction after BTX-A injections. Considerable improvement of symptoms for the BS and HFS patients was observed 7 days, 4 weeks, 12 weeks, and 24 weeks after the injection with either current Botox or CBTX-A (p < 0.05). There was no significant difference in the effectiveness rate for both HFS patients and BS patients between CBTX-A group and Botox group (p > 0.05). No statistical differences were noted in adverse reactions between them (p > 0.05). CONCLUSION: The two preparations were both simple and effective for the patients with blepharospasm and hemifacial spasm.

Structure-function relationship of king cobra cathelicidin.

King cobra cathelicidin (OH-CATH) is composed of 34 amino acid residues having strong antibacterial and very weak hemolytic activities as reported by us recently. OH-CATH can be served as a valuable template to develop novel therapeutic drugs. In this study, OH-CATH and six of its analogs were synthesized to explore their structure-function relationships based on their bactericidal and hemolytic activities. Experimental results of OH-CATH(3-34) and OH-CATH(5-34) indicated that the N-terminal 4 amino acid residues of OH-CATH played an important role on its hemolytic activity but had weak effects on its bactericidal activity. Among OH-CATH and its analogs, OH-CATH(5-34) had the lowest hemolytic activity while maintained strong antimicrobial activity. To evaluate its potential usage, the biological activities of OH-CATH(5-34) were compared with those of pexiganan. The bactericidal activity of OH-CATH(5-34) against 5 different species (11 laboratory strains) was 2-4 times stronger than that of pexiganan (4-16 microg/ml vs 8-32 microg/ml). Hemolytic activity of OH-CATH(5-34) against human erythrocytes was 0.69% while that of pexiganan was 16.5% at the dosage of 200 microg/ml. OH-CATH(5-34) showed very weak cytotoxic activities against primary rabbit ventricular endothelial cells and four human cancer cell lines whereas pexiganan showed strong cytotoxic activity against these five cell lines (IC(50)=20-90 microg/ml). The intravenous LD(50) value of OH-CATH(5-34) on mice was 7-fold higher than that of pexiganan (175 mg/kg vs 25mg/kg). Taken together, our results suggested that OH-CATH(5-34) should be considered as an excellent candidate for developing therapeutic drugs.

[Distribution and significance of α1-adrenoceptor subtypes in patients with chronic prostatitis in prostate, bladder detrusor and posterior urethral tissue].

OBJECTIVE: To study the distribution of alpha1-adrenoceptor (α1-AR) subtype in prostate, posterior urethra and bladder detrusor of patients with chronic prostatitis (CP). METHODS: The prostate specimens were collected at autopsy from 30 organ donors (aged 20-35 years old) dying of non-prostatic diseases. The pathological specimens of prostate peripheral zone were examined. The method of real-time reverse transcriptase polymerase chain reaction (real-time RT-PCR) was employed for quantification of α1a-AR and α1b-AR subtype expression in prostate transition zone and its surrounding zone, posterior urethra and bladder detrusor tissue. RESULTS: Among all donors, there were 24 cases with pathological inflammation in prostatic peripheral zone and 6 with pathological non-inflammation. The mRNA expression of α1-AR subtypes in bladder detrusor and posterior urethra was significantly higher in the inflammation group than in the control group (P<0.05). While the mRNA expression of α1-AR subtypes in the bladder detrusor and posterior urethra was significantly lower in the inflammation group than in the control group (P<0.05). CONCLUSION: An abnormal expression of α1-AR subtypes in bladder detrusor and posterior urethra may explain various urodynamic changes in CP and lead to the occurrence and development of CP in prostate, posterior urethra and bladder detrusor.

[Isolation of low-molecular-mass antibacterial mixtures from human seminal plasma].

OBJECTIVE: To isolate low-molecular-mass antibacterial mixtures from healthy human seminal plasma. METHODS: Semen was obtained by masturbation after at least three days of abstinence from healthy donors. Semen samples were allowed to liquefy at room temperature and then centrifuged at 10,000 r/min for 10 min to separate spermatozoa from seminal plasma. High sensitive antimicrobial activity was measured with radial diffusion assay. Antibacterial activity toward E. coli (ATCC25922) was monitored for each purification steps. The mixture of seminal plasma samples was applied to a SP-Sepharose column. Fractions which showed strong bactericidal activities, were combined and lyophilized. The lyophilized components were dissolved with Milli-Q water and applied to AKTA Superdex 75 column. Peak II of the Superdex 75 column, which showed antibacterial activity and represented the low-molecular-weight cationic fractions of the seminal plasma, was collected and lyophilized. Finally, peak II of the Superdex 75 column was applied to reverse phase HPLC C18 column. Fractions which showed strong antibacterial activity, were lyophilized and store at -20 degrees C. The molecular weight of the low-molecule-mass antibacterial mixtures was determined by Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. RESULTS: The low-molecular-mass mixtures with obviously higher antibacterial activity, which were termed HSLAMs(Human semen low-molecular-mass antibacterial mixtures), were isolated from the healthy human seminal plasma. Based on the mass spectrometry results, some molecules of RP-HPLC peaks were confirmed to be the semenogelin I derived peptides. CONCLUSION: The low-molecule-mass antibacterial mixtures may play an important role in males innate immunity. Semenogelin I derived peptides may be one of the sources of the low-molecule-mass antimicrobial mixtures in human seminal plasma.

[Changes of seminal parameters, zinc concentration and antibacterial activity in patients with non-inflammatory chronic prostatitis/chronic pelvic pain syndrome].

OBJECTIVE: To investigate the seminal parameters, zinc concentration and antibacterial activity in patients with non- inflammatory chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS). METHODS: Seminal parameters, zinc concentration and antibacterial activity of seminal plasma were detected in 60 CP/CPPS patients and 20 normal men. RESULTS: Statistically significant differences were found in the duration of semen liquefaction, sperm vitality, sperm motility, zinc concentration and antibacterial activity of the seminal plasma between the CP/CPPS and the control males ( P < 0.01). Zinc concentration was significantly correlated with the duration of sperm motility (r = 0. 272, P = 0.015) and antibacterial activity of the seminal plasma (r = 0.449, P < 0.01) in the CP/CPPS patients. CONCLUSION: CP/CPPS has a significant negative impact on semen liquefaction, sperm motility and vitality, zinc concentration and antibacterial activity of seminal plasma. The antibacterial activity of seminal plasma is positively correlated with zinc concentration and sperm motility.

Identification and characterization of novel reptile cathelicidins from elapid snakes.

Three cDNA sequences coding for elapid cathelicidins were cloned from constructed venom gland cDNA libraries of Naja atra, Bungarus fasciatus and Ophiophagus hannah. The open reading frames of the cloned elapid cathelicidins were all composed of 576bp and coded for 191 amino acid residue protein precursors. Each of the deduced elapid cathelicidin has a 22 amino acid residue signal peptide, a conserved cathelin domain of 135 amino acid residues and a mature antimicrobial peptide of 34 amino acid residues. Unlike the highly divergent cathelicidins in mammals, the nucleotide and deduced protein sequences of the three cloned elapid cathelicidins were remarkably conserved. All the elapid mature cathelicidins were predicted to be cleaved at Valine157 by elastase. OH-CATH, the deduced mature cathelicidin from king cobra, was chemically synthesized and it showed strong antibacterial activity against various bacteria with minimal inhibitory concentration of 1-20microg/ml in the presence of 1% NaCl. Meanwhile, the synthetic peptide showed no haemolytic activity toward human red blood cells even at a high dose of 200microg/ml. Phylogenetic analysis of cathelicidins from vertebrate suggested that elapid and viperid cathelicidins were grouped together in the tree. Snake cathelicidins were evolutionary closely related to the neutrophilic granule proteins (NGPs) from mouse, rat and rabbit. Snake cathelicidins also showed a close relationship with avian fowlicidins (1-3) and chicken myeloid antimicrobial peptide 27. Elapid cathelicidins might be used as models for the development of novel therapeutic drugs.

Identification of novel semenogelin I-derived antimicrobial peptide from liquefied human seminal plasma.

Semenogelin I (SgI) is one of the most abundant proteins in human seminal plasma. SgI plays a key role in sperm coagulation and spermatozoon immobilization. In addition, SgI and/or its proteolytic fragments are involved in regulating spermatozoon motility, capacitation and inhibin-like activity. However, little is known about the antibacterial activity of SgI-derived peptides. By a combination of ion-exchange, gel filtration and high-performance liquid chromatography, peptides from liquefied human seminal plasma from 40 healthy donors were isolated and characterized. N-terminal amino-acid sequencing and fast atom bombardment mass spectrometry revealed that four isolated peptides were SgI-derived, namely SgI-29 (85-113), SgI-46 (85-130), SgI-47 (85-131) and SgI-52 (85-136). Interestingly, SgI-29, SgI-46 and SgI-47 are newly identified SgI-derived peptides. Antimicrobial activity assay results indicated that synthesized SgI-29 had strong antibacterial activity toward various bacterial strains. Our results indicate that SgI can be digested into small fragments like newly identified SgI-29, SgI-46 and SgI-47 and may have diversified functions.

[Sonic hedgehog and prostate growth regulation].

Sonic hedgehog (Shh) is a key signal regulatory factor in embryonic development. It is reported that Shh signaling plays important roles in prostatic duct differentiation and matrix-epithelium interaction, and thus regulates the development, growth and cell proliferation of the prostate. A disorder in Shh signaling will lead to the production and proliferation of tumor cells. An exploration into the mechanism of Shh signaling in the normal growth and diseased condition of the prostate will offer some significant ideas for the studies on the pathogenesy of prostate diseases.

[Facilitation of Shengjingbao to spermatogenesis in oligospermia mouse models and its action mechanisms].

OBJECTIVE: To investigate the effects of Shengjingbao on spermatogenesis in the mouse model of oligospermia and its action mechanisms. METHODS: Sixty male mice were randomly divided into 4 groups, Shengjingbao (Group 1), Vitamin E (Group 2), blank model control (Group 3) and normal blank control (Group 4). The first three groups were treated by celiac injection of cyclophosphamide for 5 successive days to make models, followed by intragastric administration of Shengjingbao and Vitamin E to Group I and 2, respectively, for 36 days. And then all the mice were sacrificed. The serum testosterone (T) level was determined by radioimmunology, and a suspension was made from the testis and epididymis of one side for sperm analysis, while the testis of the other side was sliced up and stained by HE method and TUNEL technique to detect the count of Leydig cells, the layers of spermatogenic epithelia and the apoptosis of spermatogenic cells. RESULTS: Compared with Group 3, the serum T level, the layers of spermatogenic epithelia and the count of Leydig cells were obviously improved and even exceeded those in Group 2. The positive expression rate of spermatogenic cell apoptosis in Group 1 was evidently lower than Group 2 and 3. The above differences were statistically significant (P < 0.01 or P < 0.05), but no significant difference was noted between Group 1 and 4. CONCLUSION: Shengjingbao can significantly increase the count of Leydig cells, elevate the T level that influences the layers of spermatogenic epithelia, and thus enhance spermatogenesis. The action mechanisms of Shengjingbao may lie in its capacity of inhibiting the apoptosis of spermatogenic cells, increasing the layers of spermatogenic epithelia and facilitating spermatogenesis. T may play a role in inhibiting the apoptosis of spermatogenic cells.

Cloning of novel bombesin precursor cDNAs from skin of Bombina maxima.

Amphibian skin is a rich resource of bioactive peptides like proline-rich bombesin from frog Bombina maxima. A novel cDNA clone encoding a precursor protein that comprises proline-rich bombesin and a novel peptide, designated as bombestatin, was isolated from a skin cDNA library of B. maxima. The predicted primary structure of the novel peptide is WEVLLNVALIRLELLSCRSSKDQDQKESCGMHSW, in which two cysteines form a disulfide bond. A BLAST search of databases did not detect sequences with significant similarity. Bombestatin possesses dose-dependent contractile activity on rat stomach strips. The differences between cDNAs encoding PR-bombesin plus bombestatin and PR-bombesin alone are due to fragment insertions located in 3'-coding region and 3'-untranslational region, respectively.

Identification and molecular cloning of a novel neuromedin U analog from the skin secretions of toad Bombina maxima.

Amphibian skin contains rich neuropeptides. In the present study, a novel neuromedin U (NmU) analog was isolated from skin secretions of Chinese red belly toad Bombina maxima. Being 17-amino acids long, its primary structure was established as DSSGIVGRPFFLFRPRN-NH2, in which the C-terminal 8-residue segment (FFLFRPRN) is the same as that of rat NmU, while the N-terminal part DSSGIVGRP shows a great sequence variation compared with those of NmU peptides from different resources. The peptide, named Bm-NmU-17, was found to elicit concentration-dependent contractile effects on smooth muscle of rat uterus horns. The cDNA structure of the peptide, as obtained by a 3'-RACE strategy and subsequently cloning from a skin cDNA library, was found to contain a coding region of 438 nucleotides. The encoded precursor is composed of 145 amino acids with a single copy of Bm-NmU-17 located towards the C-terminus. The sequence of the peptide is preceded by a dibasic site (Lys-Arg) and followed by the sequence of Gly-Arg-Lys, providing the sites of cleavage and releasing of the mature peptide.

Cloning of bradykinin precursor cDNAs from skin of Bombina maxima reveals novel bombinakinin M antagonists and a bradykinin potential peptide.

Bombinakinin M (DLPKINRKGP-bradykinin) is a bradykinin-related peptide purified from skin secretions of the frog Bombina maxima. As previously reported, its biosynthesis is characterized by a tandem repeats with various copy numbers of the peptide and sometimes co-expressed with other structure-function distinguishable peptides. At present study, two novel cDNAs encoding bombinakinin M and its variants were cloned from a cDNA library from the skin of the frog. The encoded two precursor proteins are common in that each contains three repeats of a novel 16-amino acid peptide unit and one copy of kinestatin at their N- and C-terminal parts, respectively. They differ in that the first precursor contains two copies of bombinakinin M and the second one contains one copy of a novel bombinakinin M variant. Bombinakinin M was found to elicit concentration-dependent contractile effects on guinea pig ileum, with an EC50 value of 4 nM that is four times higher than that of bradykinin (1 nM). Interestingly, the synthetic peptide (DYTIRTRLH-amide), as deduced from the 16-amino acid peptide repeats in the newly cloned cDNAs, possessed weak inhibitory activity on the contractile effects of bombinakinin M, but not on that of bradykinin. Furthermore, the newly identified bombinakinin M variant (DLSKMSFLHG-Ile1-bradykinin), did not show contractile activity on guinea pig ileum, but showed potentiation effect on the myotropic activity of bradykinin. In a molar ratio of 1:58, it augmented the activity of bradykinin up to two-fold.

Maximins S, a novel group of antimicrobial peptides from toad Bombina maxima.

Amphibian skin secretions are rich in antimicrobial peptides acting as important components of innate defense system against invading microorganisms. A novel type of peptide, designated as maximin S, was deduced by random sequencing of 793 clones from a constructed Bombina maxima skin cDNA library. The putative primary structures of maximin S peptides can be grouped into five species, in which maximin S1 has 14 amino acid residues and the rest of maximin S peptides (S2-S5) all have 18 amino acid residues. Unlike most of the amphibian antimicrobial peptides so far identified, the newly characterized four maximin S precursors are composed of maximin S1 and different combinations of tandem repeated maximin S2-S5 linked by internal peptides. Except maximin S1, the predicted secondary structures of maximin S2-S5 show a similar amphipathic alpha-helical structure. MALDI-TOF mass spectrometry analysis of partially isolated skin secretions of the toad indicates that most of the deduced maximin S peptides are expressed. Two deduced maximin S peptides (S1, S4) were synthesized and their antimicrobial activities were tested. Maximin S4 only had an antibiotic activity against mycoplasma and had no antibacterial or antifungal activity toward tested strains. Maximin S1 had no activity under the same conditions.

Antimicrobial peptides from skin secretions of Chinese red belly toad Bombina maxima.

Two groups of antimicrobial peptides have been isolated from skin secretions of Bombina maxima. Peptides in the first group, named maximins 1, 2, 3, 4 and 5, are structurally related to bombinin-like peptides (BLPs). Unlike BLPs, sequence variations in maximins occurred all through the molecules. In addition to the potent antimicrobial activity, cytotoxicity against tumor cells and spermicidal action of maximins, maximin 3 possessed a significant anti-HIV activity. Maximins 1 and 3 were toxic to mice with LD(50) values of 8.2 and 4.3 mg/kg, respectively. Peptides in the second group, termed maximins H1, H2, H3 and H4, are homologous with bombinin H peptides. cDNA sequences revealed that one maximin peptide plus one maximin H peptide derived from a common larger protein.